1
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Abstract
Hox genes encode evolutionarily conserved transcription factors that are essential for the proper development of bilaterian organisms. Hox genes are unique because they are spatially and temporally regulated during development in a manner that is dictated by their tightly linked genomic organization. Although their genetic function during embryonic development has been interrogated, less is known about how these transcription factors regulate downstream genes to direct morphogenetic events. Moreover, the continued expression and function of Hox genes at postnatal and adult stages highlights crucial roles for these genes throughout the life of an organism. Here, we provide an overview of Hox genes, highlighting their evolutionary history, their unique genomic organization and how this impacts the regulation of their expression, what is known about their protein structure, and their deployment in development and beyond.
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Affiliation(s)
- Katharine A. Hubert
- Program in Genetics, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Deneen M. Wellik
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
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2
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Merabet S, Carnesecchi J. Hox dosage and morphological diversification during development and evolution. Semin Cell Dev Biol 2022:S1084-9521(22)00360-3. [PMID: 36481343 DOI: 10.1016/j.semcdb.2022.11.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 10/15/2022] [Accepted: 11/30/2022] [Indexed: 12/12/2022]
Abstract
Hox genes encode for evolutionary conserved transcription factors that have long fascinated biologists since the observation of the first homeotic transformations in flies. Hox genes are developmental architects that instruct the formation of various and precise morphologies along the body axes in cnidarian and bilaterian species. In contrast to these highly specific developmental functions, Hox genes encode for proteins that display poorly selective DNA-binding properties in vitro. This "Hox paradox" has been partially solved with the discovery of the TALE-class cofactors, which interact with all Hox members and form versatile Hox/TALE protein complexes on DNA. Here, we describe the role of the Hox dosage as an additional molecular strategy contributing to further resolve the Hox paradox. We present several cases where the Hox dosage is involved in the formation of different morphologies in invertebrates and vertebrates, with a particular emphasis on flight appendages in insects. We also discuss how the Hox dosage could be interpreted in different types of target enhancers within the nuclear environment in vivo. Altogether our survey underlines the Hox dosage as a key mechanism for shaping Hox molecular function during development and evolution.
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3
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Jia W, Zhou X, Guo N, Zhang D, Hou M, Luo Y, Peng X, Yang X, Zhang X. A novel microdeletion upstream of HOXD13 in a Chinese family with synpolydactyly. Am J Med Genet A 2021; 188:31-36. [PMID: 34467619 DOI: 10.1002/ajmg.a.62480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 08/07/2021] [Accepted: 08/13/2021] [Indexed: 11/06/2022]
Abstract
Synpolydactyly (SPD) is a digital malformation with the typical clinical phenotype of the webbing of 3/4 fingers and/or 4/5 toes, and combined with polydactyly. In this study, we investigated a Chinese family with SPD and genetic analysis found that all of the affected individuals in the family carry a heterozygous 11,451 bp microdeletion at chr2:176933872-176945322 (GRCh37), which is located upstream of HOXD13 gene, the known disease gene for SPD1. All the affected individuals in the family carry the heterozygous deletion variant, and the variant co-segregated with SPD in the family. Thus, we speculate that the 11,451 bp microdeletion is the disease-causing variant in the family. To date, the microdeletion associating with SPD1 which we identified is the smallest deletion upstream of the HOXD13 gene and not altering the sequence of the HOXD13 gene.
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Affiliation(s)
- Weimin Jia
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xiaopei Zhou
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Naiqiang Guo
- Women and Children's Hospital, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Dazhi Zhang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Meiqi Hou
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yalin Luo
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xuejie Peng
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xue Yang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xianqin Zhang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
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4
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Bolt CC, Lopez-Delisle L, Mascrez B, Duboule D. Mesomelic dysplasias associated with the HOXD locus are caused by regulatory reallocations. Nat Commun 2021; 12:5013. [PMID: 34408147 PMCID: PMC8373931 DOI: 10.1038/s41467-021-25330-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 08/05/2021] [Indexed: 02/07/2023] Open
Abstract
Human families with chromosomal rearrangements at 2q31, where the human HOXD locus maps, display mesomelic dysplasia, a severe shortening and bending of the limb. In mice, the dominant Ulnaless inversion of the HoxD cluster produces a similar phenotype suggesting the same origin for these malformations in humans and mice. Here we engineer 1 Mb inversion including the HoxD gene cluster, which positioned Hoxd13 close to proximal limb enhancers. Using this model, we show that these enhancers contact and activate Hoxd13 in proximal cells, inducing the formation of mesomelic dysplasia. We show that a secondary Hoxd13 null mutation in-cis with the inversion completely rescues the alterations, demonstrating that ectopic HOXD13 is directly responsible for this bone anomaly. Single-cell expression analysis and evaluation of HOXD13 binding sites suggests that the phenotype arises primarily by acting through genes normally controlled by HOXD13 in distal limb cells. Altogether, these results provide a conceptual and mechanistic framework to understand and unify the molecular origins of human mesomelic dysplasia associated with 2q31.
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MESH Headings
- Abnormalities, Multiple/embryology
- Abnormalities, Multiple/genetics
- Abnormalities, Multiple/metabolism
- Animals
- Bone Diseases, Developmental/embryology
- Bone Diseases, Developmental/genetics
- Bone Diseases, Developmental/metabolism
- Disease Models, Animal
- Female
- Gene Deletion
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- Humans
- Limb Deformities, Congenital/embryology
- Limb Deformities, Congenital/genetics
- Limb Deformities, Congenital/metabolism
- Loss of Function Mutation
- Male
- Mice, Inbred C57BL
- Multigene Family
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Mice
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Affiliation(s)
- Christopher Chase Bolt
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
| | - Lucille Lopez-Delisle
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Bénédicte Mascrez
- Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland
| | - Denis Duboule
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
- Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland.
- Collège de France, Paris, France.
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5
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Le Caignec C, Pichon O, Briand A, de Courtivron B, Bonnard C, Lindenbaum P, Redon R, Schluth-Bolard C, Diguet F, Rollat-Farnier PA, Sanchez-Castro M, Vuillaume ML, Sanlaville D, Duboule D, Mégarbané A, Toutain A. Fryns type mesomelic dysplasia of the upper limbs caused by inverted duplications of the HOXD gene cluster. Eur J Hum Genet 2019; 28:324-332. [PMID: 31591517 DOI: 10.1038/s41431-019-0522-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 07/12/2019] [Accepted: 09/17/2019] [Indexed: 01/09/2023] Open
Abstract
The HoxD cluster is critical for vertebrate limb development. Enhancers located in both the telomeric and centromeric gene deserts flanking the cluster regulate the transcription of HoxD genes. In rare patients, duplications, balanced translocations or inversions misregulating HOXD genes are responsible for mesomelic dysplasia of the upper and lower limbs. By aCGH, whole-genome mate-pair sequencing, long-range PCR and fiber fluorescent in situ hybridization, we studied patients from two families displaying mesomelic dysplasia limited to the upper limbs. We identified microduplications including the HOXD cluster and showed that microduplications were in an inverted orientation and inserted between the HOXD cluster and the telomeric enhancers. Our results highlight the existence of an autosomal dominant condition consisting of isolated ulnar dysplasia caused by microduplications inserted between the HOXD cluster and the telomeric enhancers. The duplications likely disconnect the HOXD9 to HOXD11 genes from their regulatory sequences. This presumptive loss-of-function may have contributed to the phenotype. In both cases, however, these rearrangements brought HOXD13 closer to telomeric enhancers, suggesting that the alterations derive from the dominant-negative effect of this digit-specific protein when ectopically expressed during the early development of forearms, through the disruption of topologically associating domain structure at the HOXD locus.
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Affiliation(s)
- Cédric Le Caignec
- CHU Nantes, Service de Génétique Médicale, Nantes, France. .,Universite de Nantes, Nantes, France.
| | - Olivier Pichon
- CHU Nantes, Service de Génétique Médicale, Nantes, France
| | - Annaig Briand
- CHU Nantes, Service de Génétique Médicale, Nantes, France
| | | | - Christian Bonnard
- Service de Chirurgie Orthopédique Pédiatrique, CHRU de Tours, Tours, France.,Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, Tours, France
| | - Pierre Lindenbaum
- INSERM, UMR_S1087, l'institut du thorax, Nantes, France.,CNRS, UMR 6291, Nantes, France
| | - Richard Redon
- INSERM, UMR_S1087, l'institut du thorax, Nantes, France.,CNRS, UMR 6291, Nantes, France
| | - Caroline Schluth-Bolard
- Department of Genetics, Lyon University Hospital, Lyon, France.,Claude Bernard Lyon I University, Lyon, France.,CRNL, CNRS UMR 5292, INSERM U1028, Lyon, France
| | - Flavie Diguet
- Department of Genetics, Lyon University Hospital, Lyon, France
| | | | | | - Marie-Laure Vuillaume
- Service de Génétique, Hôpital Bretonneau, CHU, Tours, France.,UMR 1253, iBrain, Université de Tours, Inserm, Tours, France
| | - Damien Sanlaville
- Department of Genetics, Lyon University Hospital, Lyon, France.,Claude Bernard Lyon I University, Lyon, France.,CRNL, CNRS UMR 5292, INSERM U1028, Lyon, France
| | - Denis Duboule
- University of Geneva and Federal Institute of Technology (EPFL), Lausanne, Switzerland
| | | | - Annick Toutain
- Service de Génétique, Hôpital Bretonneau, CHU, Tours, France.,UMR 1253, iBrain, Université de Tours, Inserm, Tours, France
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6
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Abstract
Vertebrate Hox genes are clustered. This organization has a functional relevance, as the transcription of each gene in time and space depends upon its relative position within the gene cluster. Hox clusters display a high organization, and all genes are transcribed from the same DNA strand. Here, we investigate the importance of this uniform transcriptional polarity by engineering alleles where one or several transcription units are inverted, with or without a CTCF site. We observe that inversions are likely detrimental to the proper implementation of this genetic system. We propose that the enhanced organization of Hox clusters in vertebrates evolved in conjunction with the emergence of global gene regulation to optimize a coordinated response of selected subsets of target genes. In many animal species with a bilateral symmetry, Hox genes are clustered either at one or at several genomic loci. This organization has a functional relevance, as the transcriptional control applied to each gene depends upon its relative position within the gene cluster. It was previously noted that vertebrate Hox clusters display a much higher level of genomic organization than their invertebrate counterparts. The former are always more compact than the latter, they are generally devoid of repeats and of interspersed genes, and all genes are transcribed by the same DNA strand, suggesting that particular factors constrained these clusters toward a tighter structure during the evolution of the vertebrate lineage. Here, we investigate the importance of uniform transcriptional orientation by engineering several alleles within the HoxD cluster, such as to invert one or several transcription units, with or without a neighboring CTCF site. We observe that the association between the tight structure of mammalian Hox clusters and their regulation makes inversions likely detrimental to the proper implementation of this complex genetic system. We propose that the consolidation of Hox clusters in vertebrates, including transcriptional polarity, evolved in conjunction with the emergence of global gene regulation via the flanking regulatory landscapes, to optimize a coordinated response of selected subsets of target genes in cis.
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7
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Rodríguez-Carballo E, Lopez-Delisle L, Zhan Y, Fabre PJ, Beccari L, El-Idrissi I, Huynh THN, Ozadam H, Dekker J, Duboule D. The HoxD cluster is a dynamic and resilient TAD boundary controlling the segregation of antagonistic regulatory landscapes. Genes Dev 2017; 31:2264-2281. [PMID: 29273679 PMCID: PMC5769770 DOI: 10.1101/gad.307769.117] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Accepted: 11/21/2017] [Indexed: 12/11/2022]
Abstract
The mammalian HoxD cluster lies between two topologically associating domains (TADs) matching distinct enhancer-rich regulatory landscapes. During limb development, the telomeric TAD controls the early transcription of Hoxd genes in forearm cells, whereas the centromeric TAD subsequently regulates more posterior Hoxd genes in digit cells. Therefore, the TAD boundary prevents the terminal Hoxd13 gene from responding to forearm enhancers, thereby allowing proper limb patterning. To assess the nature and function of this CTCF-rich DNA region in embryos, we compared chromatin interaction profiles between proximal and distal limb bud cells isolated from mutant stocks where various parts of this boundary region were removed. The resulting progressive release in boundary effect triggered inter-TAD contacts, favored by the activity of the newly accessed enhancers. However, the boundary was highly resilient, and only a 400-kb deletion, including the whole-gene cluster, was eventually able to merge the neighboring TADs into a single structure. In this unified TAD, both proximal and distal limb enhancers nevertheless continued to work independently over a targeted transgenic reporter construct. We propose that the whole HoxD cluster is a dynamic TAD border and that the exact boundary position varies depending on both the transcriptional status and the developmental context.
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Affiliation(s)
| | - Lucille Lopez-Delisle
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Ye Zhan
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Pierre J Fabre
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Leonardo Beccari
- Department of Genetics and Evolution, University of Geneva, 1205 Geneva, Switzerland
| | - Imane El-Idrissi
- Department of Genetics and Evolution, University of Geneva, 1205 Geneva, Switzerland
| | - Thi Hanh Nguyen Huynh
- Department of Genetics and Evolution, University of Geneva, 1205 Geneva, Switzerland
| | - Hakan Ozadam
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Job Dekker
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Denis Duboule
- Department of Genetics and Evolution, University of Geneva, 1205 Geneva, Switzerland
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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8
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Abstract
During embryonic development, Hox genes participate in the building of a functional digestive system in metazoans, and genetic conditions involving these genes lead to important, sometimes lethal, growth retardation. Recently, this phenotype was obtained after deletion of Haglr, the Hoxd antisense growth-associated long noncoding RNA (lncRNA) located between Hoxd1 and Hoxd3 In this study, we have analyzed the function of Hoxd genes in delayed growth trajectories by looking at several nested targeted deficiencies of the mouse HoxD cluster. Mutant pups were severely stunted during the suckling period, but many recovered after weaning. After comparing seven distinct HoxD alleles, including CRISPR/Cas9 deletions involving Haglr, we identified Hoxd3 as the critical component for the gut to maintain milk-digestive competence. This essential function could be abrogated by the dominant-negative effect of HOXD10 as shown by a genetic rescue approach, thus further illustrating the importance of posterior prevalence in Hox gene function. A role for the lncRNA Haglr in the control of postnatal growth could not be corroborated.
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9
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Possible rules for the ancestral origin of Hox gene collinearity. J Theor Biol 2016; 410:1-8. [DOI: 10.1016/j.jtbi.2016.09.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 08/12/2016] [Accepted: 09/09/2016] [Indexed: 02/07/2023]
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10
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Balogová M, Nelson E, Uhrin M, Figurová M, Ledecký V, Zyśk B. No Sexual Dimorphism Detected in Digit Ratios of the Fire Salamander (Salamandra salamandra). Anat Rec (Hoboken) 2015. [PMID: 26199217 DOI: 10.1002/ar.23197] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
It has been proposed that digit ratio may be used as a biomarker of early developmental effects. Specifically, the second-to-fourth digit ratio (2D:4D) has been linked to the effects of sex hormones and their receptor genes, but other digit ratios have also been investigated. Across taxa, patterns of sexual dimorphism in digit ratios are ambiguous and a scarcity of studies in basal tetrapods makes it difficult to understand how ratios have evolved. Here, we focus on examining sex differences in digit ratios (2D:3D, 2D:4D, and 3D:4D) in a common amphibian, the fire salamander (Salamandra salamandra). We used graphic software to measure soft tissue digit length and digit bone length from X-rays. We found a nonsignificant tendency in males to have a lower 2D:3D than females; however, no sexual differences were detected in the other ratios. We discuss our results in the context of other studies of digit ratios, and how sex determination systems, as well as other factors, might impact patterns of sexual dimorphism, particularly in reptiles and in amphibians. Our findings suggest that caution is needed when using digit ratios as a potential indicator of prenatal hormonal effects in amphibians and highlight the need for more comparative studies to elucidate the evolutionary and genetic mechanisms implicated in sexually dimorphic patterns across taxonomic groups.
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Affiliation(s)
- Monika Balogová
- Institute of Biology and Ecology, Faculty of Science, P. J. Šafárik University, Košice, Slovakia
| | - Emma Nelson
- School of Medicine, University of Liverpool, Liverpool, United Kingdom.,Archaeology, Classics and Egyptology, University of Liverpool, Liverpool, United Kingdom
| | - Marcel Uhrin
- Institute of Biology and Ecology, Faculty of Science, P. J. Šafárik University, Košice, Slovakia.,Department of Forest Protection and Wildlife Management, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Praha 6, Czech Republic
| | - Mária Figurová
- Clinic of Small Animals, University of Veterinary Medicine and Pharmacy, Košice, Slovakia
| | - Valent Ledecký
- Clinic of Small Animals, University of Veterinary Medicine and Pharmacy, Košice, Slovakia
| | - Bartłomiej Zyśk
- Department of Vertebrate Zoology and Human Biology, Institute of Biology, Cracow Pedagogical University, Kraków, Poland
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11
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Srivastava S, Dhawan J, Mishra RK. Epigenetic mechanisms and boundaries in the regulation of mammalian Hox clusters. Mech Dev 2015; 138 Pt 2:160-169. [PMID: 26254900 DOI: 10.1016/j.mod.2015.07.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 07/29/2015] [Accepted: 07/30/2015] [Indexed: 01/07/2023]
Abstract
Hox gene expression imparts segment identity to body structures along the anterior-posterior axis and is tightly governed by higher order chromatin mechanisms. Chromatin regulatory features of the homeotic complex are best defined in Drosophila melanogaster, where multiple cis-regulatory elements have been identified that ensure collinear Hox gene expression patterns in accordance with their genomic organization. Recent studies focused on delineating the epigenetic features of the vertebrate Hox clusters have helped reveal their dynamic chromatin organization and its impact on gene expression. Enrichment for the 'activating' H3K4me3 and 'repressive' H3K27me3 histone modifications is a particularly strong read-out for transcriptional status and correlates well with the evidence for chromatin loop domain structures and stage specific topological changes at these loci. However, it is not clear how such distinct domains are imposed and regulated independent of each other. Comparative analysis of the chromatin structure and organization of the homeotic gene clusters in fly and mammals is increasingly revealing the functional conservation of chromatin mediated mechanisms. Here we discuss the case for interspersed boundary elements existing within mammalian Hox clusters along with their possible roles and mechanisms of action. Recent studies suggest a role for factors other than the well characterized vertebrate boundary factor CTCF, such as the GAGA binding factor (GAF), in maintaining chromatin domains at the Hox loci. We also present data demonstrating how such regulatory elements may be involved in organizing higher order structure and demarcating active domains of gene expression at the mammalian Hox clusters.
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Affiliation(s)
- Surabhi Srivastava
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India.
| | - Jyotsna Dhawan
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India
| | - Rakesh K Mishra
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India
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12
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Hox gene regulation and timing in embryogenesis. Semin Cell Dev Biol 2014; 34:76-84. [PMID: 24930771 DOI: 10.1016/j.semcdb.2014.06.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 05/15/2014] [Accepted: 06/05/2014] [Indexed: 11/22/2022]
Abstract
Hox genes are critical regulators of embryonic development in bilaterian animals. They exhibit a unique mode of transcriptional regulation where the position of the genes along the chromosome corresponds to the time and place of their expression during development. The sequential temporal activation of these genes in the primitive streak helps determining their subsequent pattern of expression along the anterior-posterior axis of the embryo, yet the precise correspondence between these two collinear processes is not fully understood. In addition, vertebrate Hox genes evolved similar modes of regulation along secondary body axes, such as the developing limbs. We review the current understanding of the mechanisms operating during activation, maintenance and silencing of Hox gene expression in these various contexts, and discuss the evolutionary significance of their genomic organization.
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13
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Ahn Y, Mullan HE, Krumlauf R. Long-range regulation by shared retinoic acid response elements modulates dynamic expression of posterior Hoxb genes in CNS development. Dev Biol 2014; 388:134-44. [PMID: 24525295 DOI: 10.1016/j.ydbio.2014.01.027] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 01/13/2014] [Accepted: 01/31/2014] [Indexed: 10/25/2022]
Abstract
Retinoic acid (RA) signaling plays an important role in determining the anterior boundary of Hox gene expression in the neural tube during embryogenesis. In particular, RA signaling is implicated in a rostral expansion of the neural expression domain of 5׳ Hoxb genes (Hoxb9-Hoxb5) in mice. However, underlying mechanisms for this gene regulation have remained elusive due to the lack of RA responsive element (RARE) in the 5׳ half of the HoxB cluster. To identify cis-regulatory elements required for the rostral expansion, we developed a recombineering technology to serially label multiple genes with different reporters in a single bacterial artificial chromosome (BAC) vector containing the mouse HoxB cluster. This allowed us to simultaneously monitor the expression of multiple genes. In contrast to plasmid-based reporters, transgenic BAC reporters faithfully recapitulated endogenous gene expression patterns of the Hoxb genes including the rostral expansion. Combined inactivation of two RAREs, DE-RARE and ENE-RARE, in the BAC completely abolished the rostral expansion of the 5׳ Hoxb genes. Knock-out of endogenous DE-RARE lead to significantly reduced expression of multiple Hoxb genes and attenuated Hox gene response to exogenous RA treatment in utero. Regulatory potential of DE-RARE was further demonstrated by its ability to anteriorize 5׳ Hoxa gene expression in the neural tube when inserted into a HoxA BAC reporter. Our data demonstrate that multiple RAREs cooperate to remotely regulate 5׳ Hoxb genes during CNS development, providing a new insight into the mechanisms for gene regulation within the Hox clusters.
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Affiliation(s)
- Youngwook Ahn
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Hillary E Mullan
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Robb Krumlauf
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Anatomy and Cell Biology, Kansas University Medical Center, Kansas City, KS 66160, USA.
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14
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Tschopp P, Duboule D. The genetics of murine Hox loci: TAMERE, STRING, and PANTHERE to engineer chromosome variants. Methods Mol Biol 2014; 1196:89-102. [PMID: 25151159 DOI: 10.1007/978-1-4939-1242-1_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Following their duplications at the base of the vertebrate clade, Hox gene clusters underwent remarkable sub- and neo-functionalization events. Many of these evolutionary innovations can be associated with changes in the transcriptional regulation of their genes, where an intricate relationship between the structure of the gene cluster and the architecture of the surrounding genomic landscape is at play. Here, we report on a portfolio of in vivo genome engineering strategies in mice, which have been used to probe and decipher the genetic and molecular underpinnings of the complex regulatory mechanisms implemented at these loci.
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Affiliation(s)
- Patrick Tschopp
- Department of Genetics, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA
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15
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Casaca A, Santos AC, Mallo M. Controlling Hox gene expression and activity to build the vertebrate axial skeleton. Dev Dyn 2013; 243:24-36. [DOI: 10.1002/dvdy.24007] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/18/2013] [Accepted: 06/21/2013] [Indexed: 11/10/2022] Open
Affiliation(s)
- Ana Casaca
- Instituto Gulbenkian de Ciência; Oeiras Portugal
| | | | - Moisés Mallo
- Instituto Gulbenkian de Ciência; Oeiras Portugal
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16
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Transgene- and locus-dependent imprinting reveals allele-specific chromosome conformations. Proc Natl Acad Sci U S A 2013; 110:11946-51. [PMID: 23818637 DOI: 10.1073/pnas.1310704110] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
When positioned into the integrin α-6 gene, an Hoxd9lacZ reporter transgene displayed parental imprinting in mouse embryos. While the expression from the paternal allele was comparable with patterns seen for the same transgene when present at the neighboring HoxD locus, almost no signal was scored at this integration site when the transgene was inherited from the mother, although the Itga6 locus itself is not imprinted. The transgene exhibited maternal allele-specific DNA hypermethylation acquired during oogenesis, and its expression silencing was reversible on passage through the male germ line. Histone modifications also corresponded to profiles described at known imprinted loci. Chromosome conformation analyses revealed distinct chromatin microarchitectures, with a more compact structure characterizing the maternally inherited repressed allele. Such genetic analyses of well-characterized transgene insertions associated with a de novo-induced parental imprint may help us understand the molecular determinants of imprinting.
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Picchi J, Trombi L, Spugnesi L, Barachini S, Maroni G, Brodano GB, Boriani S, Valtieri M, Petrini M, Magli MC. HOX and TALE signatures specify human stromal stem cell populations from different sources. J Cell Physiol 2013; 228:879-89. [PMID: 23018864 DOI: 10.1002/jcp.24239] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 09/24/2012] [Indexed: 12/30/2022]
Abstract
Human stromal stem cell populations reside in different tissues and anatomical sites, however a critical question related to their efficient use in regenerative medicine is whether they exhibit equivalent biological properties. Here, we compared cellular and molecular characteristics of stromal stem cells derived from the bone marrow, at different body sites (iliac crest, sternum, and vertebrae) and other tissues (dental pulp and colon). In particular, we investigated whether homeobox genes of the HOX and TALE subfamilies might provide suitable markers to identify distinct stromal cell populations, as HOX proteins control cell positional identity and, together with their co-factors TALE, are involved in orchestrating differentiation of adult tissues. Our results show that stromal populations from different sources, although immunophenotypically similar, display distinct HOX and TALE signatures, as well as different growth and differentiation abilities. Stromal stem cells from different tissues are characterized by specific HOX profiles, differing in the number and type of active genes, as well as in their level of expression. Conversely, bone marrow-derived cell populations can be essentially distinguished for the expression levels of specific HOX members, strongly suggesting that quantitative differences in HOX activity may be crucial. Taken together, our data indicate that the HOX and TALE profiles provide positional, embryological and hierarchical identity of human stromal stem cells. Furthermore, our data suggest that cell populations derived from different body sites may not represent equivalent cell sources for cell-based therapeutical strategies for regeneration and repair of specific tissues.
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Affiliation(s)
- Jacopo Picchi
- Institute of Biomedical Technologies, National Research Council, Pisa, Italy
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18
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Montavon T, Duboule D. Chromatin organization and global regulation of Hox gene clusters. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120367. [PMID: 23650639 PMCID: PMC3682730 DOI: 10.1098/rstb.2012.0367] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
During development, a properly coordinated expression of Hox genes, within their different genomic clusters is critical for patterning the body plans of many animals with a bilateral symmetry. The fascinating correspondence between the topological organization of Hox clusters and their transcriptional activation in space and time has served as a paradigm for understanding the relationships between genome structure and function. Here, we review some recent observations, which revealed highly dynamic changes in the structure of chromatin at Hox clusters, in parallel with their activation during embryonic development. We discuss the relevance of these findings for our understanding of large-scale gene regulation.
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Affiliation(s)
- Thomas Montavon
- National Research Centre 'Frontiers in Genetics', School of Life Sciences, Ecole Polytechnique Fédérale, Lausanne, Switzerland
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Srivastava S, Puri D, Garapati HS, Dhawan J, Mishra RK. Vertebrate GAGA factor associated insulator elements demarcate homeotic genes in the HOX clusters. Epigenetics Chromatin 2013; 6:8. [PMID: 23607454 PMCID: PMC3639804 DOI: 10.1186/1756-8935-6-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Accepted: 04/02/2013] [Indexed: 11/10/2022] Open
Abstract
Background Hox genes impart segment identity to body structures along the anterior-posterior axis and are crucial for the proper development of all organisms. Multiple regulatory elements, best defined in Drosophila melanogaster, ensure that Hox expression patterns follow the spatial and temporal colinearity reflected in their tight genomic organization. However, the precise mechanisms that regulate colinear patterns of Hox gene expression remain unclear, especially in higher vertebrates where it is not fully determined how the distinct activation domains of the tightly clustered Hox genes are defined independently of each other. Here, we report the identification of a large number of novel cis-elements at mammalian Hox clusters that can help in regulating their precise expression pattern. Results We have identified DNA elements at all four murine Hox clusters that show poor association with histone H3 in chromatin immunoprecipitation (ChIP)-chip tiling arrays. The majority of these elements lie in the intergenic regions segregating adjacent Hox genes; we demonstrate that they possess efficient enhancer-blocking activity in mammalian cells. Further, we find that these histone-free intergenic regions bear GA repeat motifs and associate with the vertebrate homolog of the GAGA binding boundary factor. This suggests that they can act as GAGA factor-dependent chromatin boundaries that create independent domains, insulating each Hox gene from the influence of neighboring regulatory elements. Conclusions Our results reveal a large number of potential regulatory elements throughout the murine Hox clusters. We further demarcate the precise location of several novel cis-elements bearing chromatin boundary activity that appear to segregate successive Hox genes. This reflects a pattern reminiscent of the organization of homeotic genes in Drosophila, where such regulatory elements have been characterized. Our findings thus provide new insights into the regulatory processes and evolutionarily conserved epigenetic mechanisms that control homeotic gene expression.
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Affiliation(s)
- Surabhi Srivastava
- Centre for Cellular and Molecular Biology, Council for Scientific and Industrial Research, Uppal Road, Hyderabad, 500007, India.
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Impact of copy number variations (CNVs) on long-range gene regulation at the HoxD locus. Proc Natl Acad Sci U S A 2012; 109:20204-11. [PMID: 23134724 DOI: 10.1073/pnas.1217659109] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Copy number variations are genomic structural variants that are frequently associated with human diseases. Among these copy number variations, duplications of DNA segments are often assumed to lead to dosage effects by increasing the copy number of either genes or their regulatory elements. We produced a series of large targeted duplications within a conserved gene desert upstream of the murine HoxD locus. This DNA region, syntenic to human 2q31-32, contains a range of regulatory elements required for Hoxd gene transcription, and it is often disrupted and/or reorganized in human genetic conditions collectively known as the 2q31 syndrome. Unexpectedly, one such duplication led to a transcriptional down-regulation in developing digits by impairing physical interactions between the target genes and their upstream regulatory elements, thus phenocopying the effect obtained when these enhancer sequences are deleted. These results illustrate the detrimental consequences of interrupting highly conserved regulatory landscapes and reveal a mechanism where genomic duplications lead to partial loss of function of nearby located genes.
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Delpretti S, Zakany J, Duboule D. A function for all posterior Hoxd genes during digit development? Dev Dyn 2012; 241:792-802. [PMID: 22374744 DOI: 10.1002/dvdy.23756] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2012] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Four posterior Hoxd genes, from Hoxd13 to Hoxd10, are collectively regulated during the development of tetrapod digits. Besides the well-documented role of Hoxd13, the function of the neighboring genes has been difficult to evaluate due to the close genetic linkage and potential regulatory interferences. We used a combination of five small nested deletions in cis, involving from two to four consecutive genes of the Hoxd13 to Hoxd9 loci, in mice, to evaluate their combined functional importance. RESULTS We show that deletions leading to a gain of function of Hoxd13, via regulatory re-allocation, generate abnormal phenotypes, in agreement with the dominant negative role of this gene. We also show that Hoxd10, Hoxd11, and Hoxd12 all seem to play a genuine role in digit development, though less compelling than that of Hoxd13. In contrast, the nearby Hoxd9 contributed no measurable function in digits. CONCLUSIONS We conclude that a slight and transient deregulation of Hoxd13 expression can readily affect the relative lengths of limb segments and that all posterior Hoxd genes likely contribute to the final limb morphology. We discuss the difficulty to clearly assess the functional share of individual genes within such a gene family, where closely located neighbors, coding for homologous proteins, are regulated by a unique circuitry and all contribute to shape the distal parts of our appendages.
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Affiliation(s)
- Saskia Delpretti
- National Research Centre Frontiers in Genetics, School of Life Sciences, Ecole Polytechnique Fédérale, Lausanne, Switzerland
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22
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Tschopp P, Duboule D. A genetic approach to the transcriptional regulation of Hox gene clusters. Annu Rev Genet 2012; 45:145-66. [PMID: 22060042 DOI: 10.1146/annurev-genet-102209-163429] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The evolution of vertebrate genomes was accompanied by an astounding increase in the complexity of their regulatory modalities. Genetic redundancy resulting from large-scale genome duplications at the base of the chordate tree was repeatedly exploited by the functional redeployment of paralogous genes via innovations in their regulatory circuits. As a paradigm of such regulatory evolution, we have extensively studied those control mechanisms at work in-cis over vertebrate Hox gene clusters. Here, we review the portfolio of genetic strategies that have been developed to tackle the intricate relationship between genomic topography and the transcriptional activities in this gene family, and we describe some of the mechanistic insights we gained by using the HoxD cluster as an example. We discuss the high heuristic value of this system in our general understanding of how changes in transcriptional regulation can diversify gene function and thereby fuel morphological evolution.
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Affiliation(s)
- Patrick Tschopp
- National Center of Competence in Research, Frontiers in Genetics, Department of Genetics and Evolution, University of Geneva, 1211 Geneva 4, Switzerland
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A regulatory archipelago controls Hox genes transcription in digits. Cell 2012; 147:1132-45. [PMID: 22118467 DOI: 10.1016/j.cell.2011.10.023] [Citation(s) in RCA: 374] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 06/11/2011] [Accepted: 10/07/2011] [Indexed: 11/22/2022]
Abstract
The evolution of digits was an essential step in the success of tetrapods. Among the key players, Hoxd genes are coordinately regulated in developing digits, where they help organize growth and patterns. We identified the distal regulatory sites associated with these genes by probing the three-dimensional architecture of this regulatory unit in developing limbs. This approach, combined with in vivo deletions of distinct regulatory regions, revealed that the active part of the gene cluster contacts several enhancer-like sequences. These elements are dispersed throughout the nearby gene desert, and each contributes either quantitatively or qualitatively to Hox gene transcription in presumptive digits. We propose that this genetic system, which we call a "regulatory archipelago," provides an inherent flexibility that may partly underlie the diversity in number and morphology of digits across tetrapods, as well as their resilience to drastic variations.
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Tschopp P, Duboule D. A regulatory 'landscape effect' over the HoxD cluster. Dev Biol 2010; 351:288-96. [PMID: 21195707 DOI: 10.1016/j.ydbio.2010.12.034] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Revised: 12/17/2010] [Accepted: 12/20/2010] [Indexed: 12/22/2022]
Abstract
Faithful expression of Hox genes in both time and space is essential for proper patterning of the primary body axis. Transgenic approaches in vertebrates have suggested that this collinear activation process is regulated in a largely gene cluster-autonomous manner. In contrast, more recently co-opted expression specificities, required in other embryonic structures, depend upon long-range enhancer sequences acting from outside the gene clusters. This regulatory dichotomy was recently questioned, since gene activation along the trunk seems to be partially regulated by signals located outside of the cluster. We investigated these alternative regulatory strategies by engineering a large inversion that precisely separates the murine HoxD complex from its centromeric neighborhood. Mutant animals displayed posterior transformations along with subtle deregulations of Hoxd genes, indicating an impact of the centromeric landscape on the fine-tuning of Hoxd gene expression. Proximal limbs were also affected, suggesting that this 'landscape effect' is generic and impacts upon regulatory mechanisms of various qualities and evolutionary origins.
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Affiliation(s)
- Patrick Tschopp
- National Research Centre-Frontiers in Genetics, Department of Zoology and Animal Biology, University of Geneva, Sciences III, Quai Ernest-Ansermet 30, Geneva, Switzerland
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25
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Mannaert A, Amemiya CT, Bossuyt F. Comparative analyses of vertebrate posterior HoxD clusters reveal atypical cluster architecture in the caecilian Typhlonectes natans. BMC Genomics 2010; 11:658. [PMID: 21106068 PMCID: PMC3091776 DOI: 10.1186/1471-2164-11-658] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 11/24/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The posterior genes of the HoxD cluster play a crucial role in the patterning of the tetrapod limb. This region is under the control of a global, long-range enhancer that is present in all vertebrates. Variation in limb types, as is the case in amphibians, can probably not only be attributed to variation in Hox genes, but is likely to be the product of differences in gene regulation. With a collection of vertebrate genome sequences available today, we used a comparative genomics approach to study the posterior HoxD cluster of amphibians. A frog and a caecilian were included in the study to compare coding sequences as well as to determine the gain and loss of putative regulatory sequences. RESULTS We sequenced the posterior end of the HoxD cluster of a caecilian and performed comparative analyses of this region using HoxD clusters of other vertebrates. We determined the presence of conserved non-coding sequences and traced gains and losses of these footprints during vertebrate evolution, with particular focus on amphibians. We found that the caecilian HoxD cluster is almost three times larger than its mammalian counterpart. This enlargement is accompanied with the loss of one gene and the accumulation of repeats in that area. A similar phenomenon was observed in the coelacanth, where a different gene was lost and expansion of the area where the gene was lost has occurred. At least one phylogenetic footprint present in all vertebrates was lost in amphibians. This conserved region is a known regulatory element and functions as a boundary element in neural tissue to prevent expression of Hoxd genes. CONCLUSION The posterior part of the HoxD cluster of Typhlonectes natans is among the largest known today. The loss of Hoxd-12 and the expansion of the intergenic region may exert an influence on the limb enhancer, by having to bypass a distance seven times that of regular HoxD clusters. Whether or not there is a correlation with the loss of limbs remains to be investigated. These results, together with data on other vertebrates show that the tetrapod Hox clusters are more variable than previously thought.
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Affiliation(s)
- An Mannaert
- Biology Department, ECOL, Amphibian Evolution Lab, Vrije Universiteit Brussel, Brussels, Belgium
| | - Chris T Amemiya
- Benaroya Research Institute at Virginia Mason and University of Washington, Seattle, USA
| | - Franky Bossuyt
- Biology Department, ECOL, Amphibian Evolution Lab, Vrije Universiteit Brussel, Brussels, Belgium
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Iimura T, Himeno A, Nakane A, Yamaguchi A. Hox Genes, a Molecular Constraint for the Development and Evolution of the Vertebrate Body Plan. J Oral Biosci 2010. [DOI: 10.1016/s1349-0079(10)80045-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Spitz F. Control of vertebrate Hox clusters by remote and global cis-acting regulatory sequences. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 689:63-78. [PMID: 20795322 DOI: 10.1007/978-1-4419-6673-5_4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Despite apparently shared structural organisation and functional roles, vertebrate Hox genes are controlled by regulatory mechanisms rather distinct from those of the prototypic Drosophila Antennapedia (ANT-C) and Bithorax (BX-C) Complexes. If individual regulatory modules have been shown to recapitulate specific Hox expression patterns, other experimental studies underscore that vertebrate Hox clusters are controlled in many of their functions in a global manner, through distinct mechanisms. We will discuss the different models that have been proposed to account for these global regulatory modes. In this context, the studies of the regulation of the HoxD complex during limb development highlighted the role of global regulatory elements and the different mechanisms associated to transform a structural organisation into distinct temporal and spatial expression domains. We will further discuss how these mechanisms may have benefited from the structure of the vertebrate homeotic clusters and reciprocally contribute to shape their evolution towards an increased level of organisation and compaction.
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Affiliation(s)
- François Spitz
- Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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Tschopp P, Tarchini B, Spitz F, Zakany J, Duboule D. Uncoupling time and space in the collinear regulation of Hox genes. PLoS Genet 2009; 5:e1000398. [PMID: 19266017 PMCID: PMC2642670 DOI: 10.1371/journal.pgen.1000398] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2008] [Accepted: 01/30/2009] [Indexed: 12/23/2022] Open
Abstract
During development of the vertebrate body axis, Hox genes are transcribed sequentially, in both time and space, following their relative positions within their genomic clusters. Analyses of animal genomes support the idea that Hox gene clustering is essential for coordinating the various times of gene activations. However, the eventual collinear ordering of the gene specific transcript domains in space does not always require genomic clustering. We analyzed these complex regulatory relationships by using mutant alleles at the mouse HoxD locus, including one that splits the cluster into two pieces. We show that both positive and negative regulatory influences, located on either side of the cluster, control an early phase of collinear expression in the trunk. Interestingly, this early phase does not systematically impact upon the subsequent expression patterns along the main body axis, indicating that the mechanism underlying temporal collinearity is distinct from those acting during the second phase. We discuss the potential functions and evolutionary origins of these mechanisms, as well as their relationship with similar processes at work during limb development. Hox genes encode proteins that control embryonic development along the head-to-tail axis. These genes are clustered in one site on the chromosome and their respective positions within the cluster determine their time and place of activation. Here, by using a large set of targeted mutations disturbing the integrity of the gene cluster, we show that the spatial organization of expression domains does not directly depend upon the timing of activation as was previously suggested. This uncoupling between space and time in the regulation of these Hox genes coincides with the existence of two major phases of regulation. The first is time-dependent and involves global regulatory influences, located outside the gene cluster, whereas the second relies upon more local regulatory elements, likely interspersed between the genes, inside the cluster. These results provide the bases for future analyses of collinear mechanisms and indicate that different types of collinearities are not necessarily related, neither in function, nor in their evolutionary histories.
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Affiliation(s)
- Patrick Tschopp
- National Research Centre “Frontiers in Genetics”, Department of Zoology and Animal Biology, University of Geneva, Sciences III, Geneva, Switzerland
| | - Basile Tarchini
- National Research Centre “Frontiers in Genetics”, Department of Zoology and Animal Biology, University of Geneva, Sciences III, Geneva, Switzerland
| | - François Spitz
- National Research Centre “Frontiers in Genetics”, Department of Zoology and Animal Biology, University of Geneva, Sciences III, Geneva, Switzerland
| | - Jozsef Zakany
- National Research Centre “Frontiers in Genetics”, Department of Zoology and Animal Biology, University of Geneva, Sciences III, Geneva, Switzerland
| | - Denis Duboule
- National Research Centre “Frontiers in Genetics”, Department of Zoology and Animal Biology, University of Geneva, Sciences III, Geneva, Switzerland
- School of Life Sciences, Federal Institute of Technology (EPFL), Lausanne, Switzerland
- * E-mail:
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Iimura T, Denans N, Pourquié O. Establishment of Hox vertebral identities in the embryonic spine precursors. Curr Top Dev Biol 2009; 88:201-34. [PMID: 19651306 DOI: 10.1016/s0070-2153(09)88007-1] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The vertebrate spine exhibits two striking characteristics. The first one is the periodic arrangement of its elements-the vertebrae-along the anteroposterior axis. This segmented organization is the result of somitogenesis, which takes place during organogenesis. The segmentation machinery involves a molecular oscillator-the segmentation clock-which delivers a periodic signal controlling somite production. During embryonic axis elongation, this signal is displaced posteriorly by a system of traveling signaling gradients-the wavefront-which depends on the Wnt, FGF, and retinoic acid pathways. The other characteristic feature of the spine is the subdivision of groups of vertebrae into anatomical domains, such as the cervical, thoracic, lumbar, sacral, and caudal regions. This axial regionalization is controlled by a set of transcription factors called Hox genes. Hox genes exhibit nested expression domains in the somites which reflect their linear arrangement along the chromosomes-a property termed colinearity. The colinear disposition of Hox genes expression domains provides a blueprint for the regionalization of the future vertebral territories of the spine. In amniotes, Hox genes are activated in the somite precursors of the epiblast in a temporal colinear sequence and they were proposed to control their progressive ingression into the nascent paraxial mesoderm. Consequently, the positioning of the expression domains of Hox genes along the anteroposterior axis is largely controlled by the timing of Hox activation during gastrulation. Positioning of the somitic Hox domains is subsequently refined through a crosstalk with the segmentation machinery in the presomitic mesoderm. In this review, we focus on our current understanding of the embryonic mechanisms that establish vertebral identities during vertebrate development.
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Di-Poï N, Zákány J, Duboule D. Distinct roles and regulations for HoxD genes in metanephric kidney development. PLoS Genet 2008; 3:e232. [PMID: 18159948 PMCID: PMC2151092 DOI: 10.1371/journal.pgen.0030232] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2007] [Accepted: 11/14/2007] [Indexed: 11/24/2022] Open
Abstract
Hox genes encode homeodomain-containing proteins that control embryonic development in multiple contexts. Up to 30 Hox genes, distributed among all four clusters, are expressed during mammalian kidney morphogenesis, but functional redundancy between them has made a detailed functional account difficult to achieve. We have investigated the role of the HoxD cluster through comparative molecular embryological analysis of a set of mouse strains carrying targeted genomic rearrangements such as deletions, duplications, and inversions. This analysis allowed us to uncover and genetically dissect the complex role of the HoxD cluster. Regulation of metanephric mesenchyme-ureteric bud interactions and maintenance of structural integrity of tubular epithelia are differentially controlled by some Hoxd genes during renal development, consistent with their specific expression profiles. We also provide evidence for a kidney-specific form of colinearity that underlies the differential expression of two distinct sets of genes located on both sides and overlapping at the Hoxd9 locus. These insights further our knowledge of the genetic control of kidney morphogenesis and may contribute to understanding certain congenital kidney malformations, including polycystic kidney disease and renal hypoplasia. Hox genes encode proteins that control embryonic development along the head-to-tail axis and in multiple organs. Here, we show that several members of this gene family are necessary for the normal development of the mammalian kidneys. These genes are clustered in one site on the chromosome and their respective positions within the group determine which component of the kidneys they will contribute to. Using a large collection of engineered mutations in this system, we show that these genes are required both for the growth of the kidneys and for their proper organization, such that mutations in some genes reduce the size of the organs, whereas mutations in others induce polycystic kidneys. Our set of genetic rearrangements also allowed us to localize the position of regulatory sequences, which control the expression of these genes during kidney development.
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Affiliation(s)
- Nicolas Di-Poï
- Department of Zoology and Animal Biology, University of Geneva, Geneva, Swizerland
| | - József Zákány
- Department of Zoology and Animal Biology, University of Geneva, Geneva, Swizerland
| | - Denis Duboule
- Department of Zoology and Animal Biology, University of Geneva, Geneva, Swizerland
- School of Life Sciences, Ecole Polytechnique Fédérale Lausanne, Lausanne, Switzerland
- * To whom correspondence should be addressed. E-mail:
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Reno PL, McCollum MA, Cohn MJ, Meindl RS, Hamrick M, Lovejoy CO. Patterns of correlation and covariation of anthropoid distal forelimb segments correspond to Hoxd expression territories. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2008; 310:240-58. [DOI: 10.1002/jez.b.21207] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Morey C, Da Silva NR, Kmita M, Duboule D, Bickmore WA. Ectopic nuclear reorganisation driven by a Hoxb1 transgene transposed into Hoxd. J Cell Sci 2008; 121:571-7. [PMID: 18252796 DOI: 10.1242/jcs.023234] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The extent to which the nuclear organisation of a gene impacts on its ability to be expressed, or whether nuclear organisation merely reflects gene expression states, remains an important but unresolved issue. A model system that has been instrumental in investigating this question utilises the murine Hox gene clusters encoding homeobox-containing proteins. Nuclear reorganisation and chromatin decondensation, initiated towards the 3' end of the clusters, accompanies activation of Hox genes in both differentiation and development, and might be linked to mechanisms underlying colinearity. To investigate this, and to delineate the cis-acting elements involved, here we analyse the nuclear behaviour of a 3' Hoxb1 transgene transposed to the 5' end of the Hoxd cluster. We show that this transgene contains the cis-acting elements sufficient to initiate ectopic local nuclear reorganisation and chromatin decondensation and to break Hoxd colinearity in the primitive streak region of the early embryo. Significantly, in rhombomere 4, the transgene is able to induce attenuated nuclear reorganisation and decondensation of Hoxd even though there is no detectable expression of the transgene at this site. This shows that reorganisation of chromosome territories and chromatin decondensation can be uncoupled from transcription itself and suggests that they can therefore operate upstream of gene expression.
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Affiliation(s)
- Céline Morey
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, Edinburgh University, Crewe Road, Edinburgh EH4 2XU, UK
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Kleinjan DA, Lettice LA. Long-range gene control and genetic disease. ADVANCES IN GENETICS 2008; 61:339-88. [PMID: 18282513 DOI: 10.1016/s0065-2660(07)00013-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The past two decades have seen great progress in the elucidation of the genetic basis of human genetic disease. Many clinical phenotypes have been linked with mutations or deletions in specific causative genes. However, it is often less recognized that in addition to the integrity of the protein-coding sequences, human health critically also depends on the spatially, temporally, and quantitatively correct expression of those genes. Genetic disease can therefore equally be caused by disruption of the regulatory mechanisms that ensure proper gene expression. The term "position effect" is used in those situations where the expression level of a gene is deleteriously affected by an alteration in its chromosomal environment, while maintaining an intact transcription unit. Here, we review recent advances in our understanding of the possible mechanisms of a number of "position effect" disease cases and discuss the findings with respect to current models for genome organization and long-range control of gene expression.
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Affiliation(s)
- Dirk A Kleinjan
- MRC Human Genetics Unit, Western General Hospital, Edinburgh EH4 2XU, United Kingdom
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Spitz F, Duboule D. Global control regions and regulatory landscapes in vertebrate development and evolution. ADVANCES IN GENETICS 2008; 61:175-205. [PMID: 18282506 DOI: 10.1016/s0065-2660(07)00006-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
During the course of evolution, many genes that control the development of metazoan body plans were co-opted to exert novel functions, along with the emergence or modification of structures. Gene amplification and/or changes in the cis-regulatory modules responsible for the transcriptional activity of these genes have certainly contributed in a major way to evolution of gene functions. In some cases, these processes led to the formation of groups of adjacent genes that appear to be controlled by both global and shared mechanisms.
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Affiliation(s)
- Francois Spitz
- Developmental Biology Unit, EMBL, 69117 Heidelberg, Germany
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35
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Sheth R, Bastida MF, Ros M. Hoxd and Gli3 interactions modulate digit number in the amniote limb. Dev Biol 2007; 310:430-41. [PMID: 17714700 DOI: 10.1016/j.ydbio.2007.07.023] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 07/18/2007] [Accepted: 07/23/2007] [Indexed: 11/17/2022]
Abstract
During limb development, Sonic hedgehog (SHH) and HOX proteins are considered among the most important factors regulating digit number and identity. SHH signaling prevents the processing of GLI3 into a short form that functions as a strong transcriptional repressor. Gli3 mutant limbs are characterized by a severe polydactyly and associated ectopic anterior expression of 5'Hoxd genes. To genetically determine the involvement of 5'Hoxd genes in the polydactyly of Gli3 mutants, we have generated a compound mutant that simultaneously removes the three most 5'-located Hoxd genes and Gli3. Remarkably, the limbs that form in the absence of all four of these genes show the most severe polydactyly so far reported in the mouse. The analysis of gene expression performed in compound mutants allows us to propose that the increase in the number of digits is mediated by the gain in function of Hoxd10 and Hoxd9. Our results also support the notion that an adequate balance between positive and negative effects of different Hoxd genes is required for pentadactyly.
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Affiliation(s)
- Rushikesh Sheth
- Departamento de Anatomía y Biología Celular, Universidad de Cantabria, 39011, Santander, Spain
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36
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Bengani H, Ganapathi M, Singh GP, Brahmachari V. Mining of putative cis-acting elements for chromatin mediated regulation of Hox genes in mammals by in-silico analysis. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2007; 308:384-95. [PMID: 17358016 DOI: 10.1002/jez.b.21162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The remarkable conservation in developmental strategies across phyla is well reflected in the conservation of the homeotic gene complexes responsible for establishing the body plan in embryonic development. On the other hand, changes in the strategy of transcription regulation are believed to form one of the major factors in the evolution of developmental mechanisms and phenotypic evolution of species. Apart from transcription regulation by gene specific transcription factors, the role of regulators mediating modifications of chromatin proteins, especially of HOX gene clusters in Drosophila is well documented. By comparative genomics we have identified novel motifs conserved in mouse, chimpanzee and human in the noncoding upstream/intronic sequences of Hox genes by in silico analysis. These motifs lack the binding sites for known transcription factors and are significantly over represented in the target genes of one of the core components of Polycomb Repressive Complex namely Supressor of zeste 12 (SUZ12) in human embryonic cells reported by Lee et al. [2006a. Cell 125:301-313]. Therefore, we predict that they could be the sites of interaction of chromatin modifying complexes for epigenetic regulation.
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Affiliation(s)
- Hemant Bengani
- Dr. B.R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi, India
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37
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Zakany J, Zacchetti G, Duboule D. Interactions between HOXD and Gli3 genes control the limb apical ectodermal ridge via Fgf10. Dev Biol 2007; 306:883-93. [PMID: 17467687 DOI: 10.1016/j.ydbio.2007.03.517] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Revised: 03/05/2007] [Accepted: 03/26/2007] [Indexed: 10/23/2022]
Abstract
The development of the vertebrate limb is dependent upon two signaling centers, the apical ectodermal ridge (AER), which provides the underlying mesenchyme with essential growth factors, and the zone of polarizing activity (ZPA), the source of the Sonic hedgehog (SHH) product. Recent work involving gain and loss of function of Hox genes has emphasized their impact both on AER maintenance and Shh transcriptional activation. Here, we describe antagonistic interactions between posterior Hoxd genes and Gli3, suggesting that the latter product protects the AER from the deleterious effect of the formers, and we present evidence that Fgf10 is the mediator of HOX-dependent AER expansion. Furthermore, the striking similarity between some of the hereby observed Hox/Gli3-dependent morphogenetic defects and those displayed by fetuses with severely altered retinoic acid metabolism suggests a tight connection between these various pathways. The nature of these potential interactions is discussed in the context of proximal-distal growth and patterning.
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Affiliation(s)
- Jozsef Zakany
- Department of Zoology and Animal Biology and National Research Centre/Frontiers in Genetics, University of Geneva, Sciences III, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland
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38
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Abstract
Vertebrae display distinct morphological features at different levels of the body axis. Links between collinear Hox gene activation and the progressive mode of body axis elongation have provided a fascinating blueprint of the mechanisms for establishing these morphological identities. In this review, we first discuss the regulation and possible role of collinear Hox gene activation during body formation and then highlight the direct role of Hox genes in controlling cellular movements during gastrulation, therefore contributing to body formation. Additional related research aspects, such as imaging of chromatin regulation, roles of micro RNAs and evolutional findings are also discussed.
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Affiliation(s)
- Tadahiro Iimura
- Howard Hughes Medical Institute, Kansas City, Missouri 64110, USA
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39
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Gonzalez F, Duboule D, Spitz F. Transgenic analysis of Hoxd gene regulation during digit development. Dev Biol 2007; 306:847-59. [PMID: 17448461 DOI: 10.1016/j.ydbio.2007.03.020] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Revised: 02/27/2007] [Accepted: 03/19/2007] [Indexed: 12/22/2022]
Abstract
In tetrapods, posterior Hoxd genes (from groups 10 to 13) are necessary to properly pattern the developing autopods, including the number and identities of digits. Their coordinated expression is achieved by sharing a global control region (GCR), which was isolated and localized 200 kb 5' (centromeric) of the gene cluster. However, in transgenic assays, the GCR was unable to fully recapitulate all aspects of the endogenous Hoxd expression patterns during distal limb development. In this paper, we further analyze the regulatory potential of this locus and report the characterization of Prox, a second enhancer element that contributes to the transcriptional activity of posterior Hoxd genes in developing distal limb buds. We show that the GCR and Prox elements complement each other and work in combination to correctly establish the late phase of Hoxd genes expression. Based on DNA sequence conservation and transgenic assays, we discuss the functions of these regulatory regions as well as a potential evolutionary scheme accounting for their emergence along with the evolution of tetrapod limbs.
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Affiliation(s)
- Federico Gonzalez
- National Center for Competence in Research/Frontiers in Genetics, Department of Zoology and Animal Biology, University of Geneva, Sciences III, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland
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40
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Morey C, Da Silva NR, Perry P, Bickmore WA. Nuclear reorganisation and chromatin decondensation are conserved, but distinct, mechanisms linked to Hox gene activation. Development 2007; 134:909-19. [PMID: 17251268 DOI: 10.1242/dev.02779] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The relocalisation of some genes to positions outside chromosome territories, and the visible decondensation or unfolding of interphase chromatin, are two striking facets of nuclear reorganisation linked to gene activation that have been assumed to be related to each other. Here, in a study of nuclear reorganisation around the Hoxd cluster, we suggest that this may not be the case. Despite its very different genomic environment from Hoxb, Hoxd also loops out from its chromosome territory, and unfolds, upon activation in differentiating embryonic stem (ES) cells and in the tailbud of the embryo. However, looping out and decondensation are not simply two different manifestations of the same underlying change in chromatin structure. We show that, in the limb bud of the embryonic day 9.5 embryo,where Hoxd is also activated, there is visible decondensation of chromatin but no detectable movement of the region out from the chromosome territory. During ES cell differentiation, decondensed alleles can also be found inside of chromosome territories, and loci that have looped out of the territories can appear to still be condensed. We conclude that evolutionarily conserved chromosome remodelling mechanisms, predating the duplication of mammalian Hox loci, underlie Hox regulation along the rostrocaudal embryonic axis. However, we suggest that separate modes of regulation can modify Hoxd chromatin in different ways in different developmental contexts.
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Affiliation(s)
- Céline Morey
- MRC Human Genetics Unit, Crewe Road, Edinburgh EH4 2XU, UK
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41
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Takamatsu N, Kurosawa G, Takahashi M, Inokuma R, Tanaka M, Kanamori A, Hori H. Duplicated Abd-B class genes in medaka hoxAa and hoxAb clusters exhibit differential expression patterns in pectoral fin buds. Dev Genes Evol 2007; 217:263-73. [PMID: 17333260 DOI: 10.1007/s00427-007-0137-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Accepted: 01/25/2007] [Indexed: 11/27/2022]
Abstract
Hox genes form clusters. Invertebrates and Amphioxus have only one hox cluster, but in vertebrates, they are multiple, i.e., four in the basal teleost fish Polyodon and tetrapods (HoxA, B, C, D), but seven or eight in common teleosts. We earlier completely sequenced the entire hox gene loci in medaka fish, showing a total of 46 hox genes to be encoded in seven clusters (hoxAa, Ab, Ba, Bb, Ca, Da, Db). Among them, hoxAa, hoxAb and hoxDa clusters are presumed to be important for fin-to-limb evolution because of their key role in forelimb and pectoral fin development. In the present study, we compared genome organization and nucleotide sequences of the hoxAa and hoxAb clusters to these of tetrapod HoxA clusters, and found greater similarity in hoxAa case. We then analyzed expression of Abd-B family genes in the clusters. In the trunk, those from the hoxAa cluster, i.e., hoxA9a, hoxA10a, hoxA11a and hoxA13a, were expressed in a manner keeping the colinearity rule of the hox expression as those of tetrapods, while those from the hoxAb cluster, i.e., hoxA9b, hoxA10b, hoxA11b and hoxA13b, were not. In the pectoral fins, the hoxAa cluster was expressed in split domains and did not obey the rule. By contrast, those from the hoxAb and hoxDa clusters were expressed in a manner keeping the rule, i.e., an ancestral pattern similar to those of tetrapods. It is plausible that this differential expression of the two clusters is caused by changes occurred in global control regions after cluster duplications.
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Affiliation(s)
- Naofumi Takamatsu
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi 464-8602, Japan
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42
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Tarchini B, Duboule D, Kmita M. Regulatory constraints in the evolution of the tetrapod limb anterior-posterior polarity. Nature 2006; 443:985-8. [PMID: 17066034 DOI: 10.1038/nature05247] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Accepted: 09/15/2006] [Indexed: 12/19/2022]
Abstract
The anterior to posterior (A-P) polarity of the tetrapod limb is determined by the confined expression of Sonic hedgehog (Shh) at the posterior margin of developing early limb buds, under the control of HOX proteins encoded by gene members of both the HoxA and HoxD clusters. Here, we use a set of partial deletions to show that only the last four Hox paralogy groups can elicit this response: that is, precisely those genes whose expression is excluded from most anterior limb bud cells owing to their collinear transcriptional activation. We propose that the limb A-P polarity is produced as a collateral effect of Hox gene collinearity, a process highly constrained by its crucial importance during trunk development. In this view, the co-option of the trunk collinear mechanism, along with the emergence of limbs, imposed an A-P polarity to these structures as the most parsimonious solution. This in turn further contributed to stabilize the architecture and operational mode of this genetic system.
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Affiliation(s)
- Basile Tarchini
- Department of Zoology and Animal Biology and National Research Centre Frontiers in Genetics, University of Geneva, Sciences III, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland
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43
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Robert B, Lallemand Y. Anteroposterior patterning in the limb and digit specification: contribution of mouse genetics. Dev Dyn 2006; 235:2337-52. [PMID: 16894622 DOI: 10.1002/dvdy.20890] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The limb has been a privileged object of investigation and reflection for scientists over the past two centuries and continues to provide a heuristic framework to analyze vertebrate development. Recently, accumulation of new data has significantly changed our view on the mechanisms of limb patterning, in particular along the anterior-posterior axis. These data have led us to revisit the mode of action of the zone of polarizing activity. They shed light on the molecular and cellular mechanisms of patterning linked to the Shh-Gli3 signaling pathway and give insights into the mechanism of activation of these cardinal factors, as well as the consequences of their activity. These new data are in good part the result of systematic Application of tools used in contemporary mouse molecular genetics. These have extended the power of mouse genetics by introducing mutational strategies that allow fine-tuned modulation of gene expression, interchromosomal deletions and duplication. They have even made the mouse embryo amenable to cell lineage analysis that used to be the realm of chick embryos. In this review, we focus on the data acquired over the last five years from the analysis of mouse limb development and discuss new perspectives opened by these results.
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Affiliation(s)
- Benoît Robert
- Department of Developmental Biology, CNRS URA 2578, Pasteur Institute, Paris, France.
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44
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Williams ME, Lehoczky JA, Innis JW. A group 13 homeodomain is neither necessary nor sufficient for posterior prevalence in the mouse limb. Dev Biol 2006; 297:493-507. [PMID: 16806154 DOI: 10.1016/j.ydbio.2006.05.027] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 05/18/2006] [Accepted: 05/22/2006] [Indexed: 01/08/2023]
Abstract
Posterior prevalence is the general property attributed to HOX proteins describing the dominant effect of more posterior HOX proteins over the function of anterior orthologs in common areas of expression. To explore the HOX group 13 protein domains required for this property, we used the mouse Prx-1 promoter to drive transgenic expression of Hox constructs throughout the entire limb bud during development. This system allowed us to conclusively demonstrate a hierarchy of Hox function in developing limbs. Furthermore, by substituting the HOXD11 or HOXA9 homeodomain for that of HOXD13, we show that a HOXD13 homeodomain is not necessary for posterior prevalence. Proximal expression of these chimeric proteins unexpectedly caused defects consistent with wild-type HOXD13 mediated posterior prevalence. Moreover, group 13 non-homeodomain residues appear to confer the property as proximal expression of HOXA9 containing the HOXD13 homeodomain did not result in limb reductions characteristic of HOXD13. These data are most compatible with models of posterior prevalence based on protein-protein interactions and support examination of the N-terminal non-homeodomain regions of Hox group 13 proteins as necessary agents for posterior prevalence.
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Affiliation(s)
- Melissa E Williams
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
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45
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Nadra K, Anghel SI, Joye E, Tan NS, Basu-Modak S, Trono D, Wahli W, Desvergne B. Differentiation of trophoblast giant cells and their metabolic functions are dependent on peroxisome proliferator-activated receptor beta/delta. Mol Cell Biol 2006; 26:3266-81. [PMID: 16581799 PMCID: PMC1446964 DOI: 10.1128/mcb.26.8.3266-3281.2006] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Mutation of the nuclear receptor peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) severely affects placenta development, leading to embryonic death at embryonic day 9.5 (E9.5) to E10.5 of most, but not all, PPARbeta/delta-null mutant embryos. While very little is known at present about the pathway governed by PPARbeta/delta in the developing placenta, this paper demonstrates that the main alteration of the placenta of PPARbeta/delta-null embryos is found in the giant cell layer. PPARbeta/delta activity is in fact essential for the differentiation of the Rcho-1 cells in giant cells, as shown by the severe inhibition of differentiation once PPARbeta/delta is silenced. Conversely, exposure of Rcho-1 cells to a PPARbeta/delta agonist triggers a massive differentiation via increased expression of 3-phosphoinositide-dependent kinase 1 and integrin-linked kinase and subsequent phosphorylation of Akt. The links between PPARbeta/delta activity in giant cells and its role on Akt activity are further strengthened by the remarkable pattern of phospho-Akt expression in vivo at E9.5, specifically in the nucleus of the giant cells. In addition to this phosphatidylinositol 3-kinase/Akt main pathway, PPARbeta/delta also induced giant cell differentiation via increased expression of I-mfa, an inhibitor of Mash-2 activity. Finally, giant cell differentiation at E9.5 is accompanied by a PPARbeta/delta-dependent accumulation of lipid droplets and an increased expression of the adipose differentiation-related protein (also called adipophilin), which may participate to lipid metabolism and/or steroidogenesis. Altogether, this important role of PPARbeta/delta in placenta development and giant cell differentiation should be considered when contemplating the potency of PPARbeta/delta agonist as therapeutic agents of broad application.
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Affiliation(s)
- Karim Nadra
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland
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46
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Corredor-Adámez M, Welten MCM, Spaink HP, Jeffery JE, Schoon RT, de Bakker MAG, Bagowski CP, Meijer AH, Verbeek FJ, Richardson MK. Genomic annotation and transcriptome analysis of the zebrafish (Danio rerio) hox complex with description of a novel member, hoxb13a. Evol Dev 2005; 7:362-75. [PMID: 16174031 DOI: 10.1111/j.1525-142x.2005.05042.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The zebrafish (Danio rerio) is an important model in evolutionary developmental biology, and its study is being revolutionized by the zebrafish genome project. Sequencing is at an advanced stage, but annotation is largely the result of in silico analyses. We have performed genomic annotation, comparative genomics, and transcriptional analysis using microarrays of the hox homeobox-containing transcription factors. These genes have important roles in specifying the body plan. Candidate sequences were located in version Z v 4 of the Ensembl genome database by TBLASTN searching with Danio and other vertebrate published Hox protein sequences. Homologies were confirmed by alignment with reference sequences, and by the relative position of genes along each cluster. RT-PCR using adult Tübingen cDNA was used to confirm annotations, to check the genomic sequence and to confirm expression in vivo. Our RT-PCR and microarray data show that all 49 hox genes are expressed in adult zebrafish. Significant expression for all known hox genes could be detected in our microarray analysis. We also find significant expression of hox 8 paralogs and hox b 7 a in the anti-sense direction. A novel gene, D. rerio hox b 13 a, was identified, and a preliminary characterization by in situ hybridization showed expression at 24 hpf at the tip of the developing tail. We are currently characterizing this gene at the functional level. We argue that the oligo design for microarrays can be greatly enhanced by the availability of genomic sequences.
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Affiliation(s)
- M Corredor-Adámez
- Institute of Biology, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands
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47
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Zuniga A. Globalisation reaches gene regulation: the case for vertebrate limb development. Curr Opin Genet Dev 2005; 15:403-9. [PMID: 15979301 DOI: 10.1016/j.gde.2005.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Accepted: 06/07/2005] [Indexed: 10/25/2022]
Abstract
Analysis of key regulators of vertebrate limb development has revealed that the cis-regulatory regions controlling their expression are often located several hundred kilobases upstream of the transcription units. These far up- or down-stream cis-regulatory regions tend to reside within rather large, functionally and structurally unrelated genes. Molecular analysis is beginning to reveal the complexity of these large genomic landscapes, which control the co-expression of clusters of diverse genes by this novel type of long-range and globally acting cis-regulatory region. An increasing number of spontaneous mutations in vertebrates, including humans, are being discovered inactivating or altering such global control regions. Thereby, the functions of a seemingly distant but essential gene are disrupted rather than the closest.
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Affiliation(s)
- Aimée Zuniga
- Developmental Genetics, DKBW Centre for Biomedicine, University of Basel Medical School, Mattenstrasse 28, CH-4058 Basel, Switzerland.
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48
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Cobb J, Duboule D. Comparative analysis of genes downstream of the Hoxd cluster in developing digits and external genitalia. Development 2005; 132:3055-67. [PMID: 15944189 DOI: 10.1242/dev.01885] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mammalian Hox genes encode transcription factors that are crucial for proper morphogenesis along the various body axes. Despite their extensive structural and functional characterization, the nature of their target genes remains elusive. We have addressed this question by using DNA microarrays to screen for genes whose expression in developing distal forelimbs and genital eminences was significantly modified in the absence of the full Hoxd gene complement. This comparative approach not only identified specific candidate genes, but also allowed the examination of whether a similar Hox expression pattern in distinct tissues leads to the modulation of the same or different downstream genes. We report here a set of potential target genes, most of which were not previously known to play a role in the early stages of either limb or genital bud development. Interestingly, we find that the majority of these candidate genes are differentially expressed in both structures,although often at different times. This supports the idea that both appendices involve similar genetic controls, both upstream and downstream of the Hox gene family. These results highlight the surprising mechanistic relationship between these rather different body parts and suggest a common developmental strategy to build up the most distal appendicular structures of the body, i.e. the digits and the penis/clitoris.
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Affiliation(s)
- John Cobb
- National Research Center (NCCR Zoology and Animal Biology, University of Geneva, Sciences III, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland
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49
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Kleinjan DA, van Heyningen V. Long-range control of gene expression: emerging mechanisms and disruption in disease. Am J Hum Genet 2005; 76:8-32. [PMID: 15549674 PMCID: PMC1196435 DOI: 10.1086/426833] [Citation(s) in RCA: 645] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2004] [Accepted: 10/08/2004] [Indexed: 02/04/2023] Open
Abstract
Transcriptional control is a major mechanism for regulating gene expression. The complex machinery required to effect this control is still emerging from functional and evolutionary analysis of genomic architecture. In addition to the promoter, many other regulatory elements are required for spatiotemporally and quantitatively correct gene expression. Enhancer and repressor elements may reside in introns or up- and downstream of the transcription unit. For some genes with highly complex expression patterns--often those that function as key developmental control genes--the cis-regulatory domain can extend long distances outside the transcription unit. Some of the earliest hints of this came from disease-associated chromosomal breaks positioned well outside the relevant gene. With the availability of wide-ranging genome sequence comparisons, strong conservation of many noncoding regions became obvious. Functional studies have shown many of these conserved sites to be transcriptional regulatory elements that sometimes reside inside unrelated neighboring genes. Such sequence-conserved elements generally harbor sites for tissue-specific DNA-binding proteins. Developmentally variable chromatin conformation can control protein access to these sites and can regulate transcription. Disruption of these finely tuned mechanisms can cause disease. Some regulatory element mutations will be associated with phenotypes distinct from any identified for coding-region mutations.
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Affiliation(s)
- Dirk A Kleinjan
- MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, Scotland, United Kingdom
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50
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