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Smith JJ, Kratsios P. Hox gene functions in the C. elegans nervous system: From early patterning to maintenance of neuronal identity. Semin Cell Dev Biol 2024; 152-153:58-69. [PMID: 36496326 PMCID: PMC10244487 DOI: 10.1016/j.semcdb.2022.11.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/14/2022] [Accepted: 11/30/2022] [Indexed: 12/12/2022]
Abstract
The nervous system emerges from a series of genetic programs that generate a remarkable array of neuronal cell types. Each cell type must acquire a distinct anatomical position, morphology, and function, enabling the generation of specialized circuits that drive animal behavior. How are these diverse cell types and circuits patterned along the anterior-posterior (A-P) axis of the animal body? Hox genes encode transcription factors that regulate cell fate and patterning events along the A-P axis of the nervous system. While most of our understanding of Hox-mediated control of neuronal development stems from studies in segmented animals like flies, mice, and zebrafish, important new themes are emerging from work in a non-segmented animal: the nematode Caenorhabditis elegans. Studies in C. elegans support the idea that Hox genes are needed continuously and across different life stages in the nervous system; they are not only required in dividing progenitor cells, but also in post-mitotic neurons during development and adult life. In C. elegans embryos and young larvae, Hox genes control progenitor cell specification, cell survival, and neuronal migration, consistent with their neural patterning roles in other animals. In late larvae and adults, C. elegans Hox genes control neuron type-specific identity features critical for neuronal function, thereby extending the Hox functional repertoire beyond early patterning. Here, we provide a comprehensive review of Hox studies in the C. elegans nervous system. To relate to readers outside the C. elegans community, we highlight conserved roles of Hox genes in patterning the nervous system of invertebrate and vertebrate animals. We end by calling attention to new functions in adult post-mitotic neurons for these paradigmatic regulators of cell fate.
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Affiliation(s)
- Jayson J Smith
- Department of Neurobiology, University of Chicago, 947 East 58th Street, Chicago, IL 60637, USA; University of Chicago Neuroscience Institute, 947 East 58th Street, Chicago, IL 60637, USA.
| | - Paschalis Kratsios
- Department of Neurobiology, University of Chicago, 947 East 58th Street, Chicago, IL 60637, USA; University of Chicago Neuroscience Institute, 947 East 58th Street, Chicago, IL 60637, USA.
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2
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Clarembaux‐Badell L, Baladrón‐de‐Juan P, Gabilondo H, Rubio‐Ferrera I, Millán I, Estella C, Valverde‐Ortega FS, Cobeta IM, Thor S, Benito‐Sipos J. Dachshund acts with Abdominal-B to trigger programmed cell death in the Drosophila central nervous system at the frontiers of Abd-B expression. Dev Neurobiol 2022; 82:495-504. [PMID: 35796156 PMCID: PMC9544350 DOI: 10.1002/dneu.22894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 06/13/2022] [Accepted: 06/21/2022] [Indexed: 11/22/2022]
Abstract
A striking feature of the nervous system pertains to the appearance of different neural cell subtypes at different axial levels. Studies in the Drosophila central nervous system reveal that one mechanism underlying such segmental differences pertains to the segment-specific removal of cells by programmed cell death (PCD). One group of genes involved in segment-specific PCD is the Hox homeotic genes. However, while segment-specific PCD is highly precise, Hox gene expression is evident in gradients, raising the issue of how the Hox gene function is precisely gated to trigger PCD in specific segments at the outer limits of Hox expression. The Drosophila Va neurons are initially generated in all nerve cord segments but removed by PCD in posterior segments. Va PCD is triggered by the posteriorly expressed Hox gene Abdominal-B (Abd-B). However, Va PCD is highly reproducible despite exceedingly weak Abd-B expression in the anterior frontiers of its expression. Here, we found that the transcriptional cofactor Dachshund supports Abd-B-mediated PCD in its anterior domain. In vivo bimolecular fluorescence complementation analysis lends support to the idea that the Dachshund/Abd-B interplay may involve physical interactions. These findings provide an example of how combinatorial codes of transcription factors ensure precision in Hox-mediated PCD in specific segments at the outer limits of Hox expression.
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Affiliation(s)
- Luis Clarembaux‐Badell
- Departamento de Biología, Facultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
| | - Pablo Baladrón‐de‐Juan
- Departamento de Biología, Facultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
| | - Hugo Gabilondo
- Departamento de Biología, Facultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
| | - Irene Rubio‐Ferrera
- Departamento de Biología, Facultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
| | - Irene Millán
- Departamento de Biología, Facultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
| | - Carlos Estella
- Departamento de Biología Molecular and Centro de Biología Molecular Severo OchoaConsejo Superior de Investigaciones Científicas‐Universidad Autónoma de Madrid (CSIC‐UAM)Nicolás Cabrera 1MadridSpain
| | - Félix S. Valverde‐Ortega
- Departamento de Biología, Facultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
| | - Ignacio Monedero Cobeta
- Departamento de Biología, Facultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
- Departamento de Fisiología, Facultad de MedicinaUniversidad Autónoma de MadridCantoblancoMadridSpain
| | - Stefan Thor
- School of Biomedical SciencesThe University of QueenslandBrisbaneAustralia
| | - Jonathan Benito‐Sipos
- Departamento de Biología, Facultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
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3
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Joshi R, Sipani R, Bakshi A. Roles of Drosophila Hox Genes in the Assembly of Neuromuscular Networks and Behavior. Front Cell Dev Biol 2022; 9:786993. [PMID: 35071230 PMCID: PMC8777297 DOI: 10.3389/fcell.2021.786993] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 12/14/2021] [Indexed: 11/13/2022] Open
Abstract
Hox genes have been known for specifying the anterior-posterior axis (AP) in bilaterian body plans. Studies in vertebrates have shown their importance in developing region-specific neural circuitry and diversifying motor neuron pools. In Drosophila, they are instrumental for segment-specific neurogenesis and myogenesis early in development. Their robust expression in differentiated neurons implied their role in assembling region-specific neuromuscular networks. In the last decade, studies in Drosophila have unequivocally established that Hox genes go beyond their conventional functions of generating cellular diversity along the AP axis of the developing central nervous system. These roles range from establishing and maintaining the neuromuscular networks to controlling their function by regulating the motor neuron morphology and neurophysiology, thereby directly impacting the behavior. Here we summarize the limited knowledge on the role of Drosophila Hox genes in the assembly of region-specific neuromuscular networks and their effect on associated behavior.
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Affiliation(s)
- Rohit Joshi
- Laboratory of Drosophila Neural Development, Centre for DNA Fingerprinting and Diagnostics (CDFD), Hyderabad, India
| | - Rashmi Sipani
- Laboratory of Drosophila Neural Development, Centre for DNA Fingerprinting and Diagnostics (CDFD), Hyderabad, India.,Graduate Studies, Manipal Academy of Higher Education, Manipal, India
| | - Asif Bakshi
- Laboratory of Drosophila Neural Development, Centre for DNA Fingerprinting and Diagnostics (CDFD), Hyderabad, India.,Graduate Studies, Manipal Academy of Higher Education, Manipal, India
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Wang M, Dai M, Wang D, Xiong W, Zeng Z, Guo C. The regulatory networks of the Hippo signaling pathway in cancer development. J Cancer 2021; 12:6216-6230. [PMID: 34539895 PMCID: PMC8425214 DOI: 10.7150/jca.62402] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 08/15/2021] [Indexed: 01/14/2023] Open
Abstract
The Hippo signaling pathway is a relatively young tumor-related signaling pathway. Although it was discovered lately, research on it developed rapidly. The Hippo signaling pathway is closely relevant to the occurrence and development of tumors and the maintenance of organ size and other biological processes. This manuscript focuses on YAP, the core molecule of the Hippo signaling pathway, and discussion the upstream and downstream regulatory networks of the Hippo signaling pathway during tumorigenesis and development. It also summarizes the relevant drugs involved in this signaling pathway, which may be helpful to the development of targeted drugs for cancer therapy.
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Affiliation(s)
- Maonan Wang
- NHC Key Laboratory of Carcinogenesis, Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Manli Dai
- Hunan Food and Drug Vocational College, Changsha 410036, China
| | - Dan Wang
- NHC Key Laboratory of Carcinogenesis, Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Wei Xiong
- NHC Key Laboratory of Carcinogenesis, Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Zhaoyang Zeng
- NHC Key Laboratory of Carcinogenesis, Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Can Guo
- NHC Key Laboratory of Carcinogenesis, Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
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Hombría JCG, García-Ferrés M, Sánchez-Higueras C. Anterior Hox Genes and the Process of Cephalization. Front Cell Dev Biol 2021; 9:718175. [PMID: 34422836 PMCID: PMC8374599 DOI: 10.3389/fcell.2021.718175] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 07/16/2021] [Indexed: 11/13/2022] Open
Abstract
During evolution, bilateral animals have experienced a progressive process of cephalization with the anterior concentration of nervous tissue, sensory organs and the appearance of dedicated feeding structures surrounding the mouth. Cephalization has been achieved by the specialization of the unsegmented anterior end of the body (the acron) and the sequential recruitment to the head of adjacent anterior segments. Here we review the key developmental contribution of Hox1-5 genes to the formation of cephalic structures in vertebrates and arthropods and discuss how this evolved. The appearance of Hox cephalic genes preceded the evolution of a highly specialized head in both groups, indicating that Hox gene involvement in the control of cephalic structures was acquired independently during the evolution of vertebrates and invertebrates to regulate the genes required for head innovation.
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Affiliation(s)
- James C-G Hombría
- Centro Andaluz de Biología del Desarrollo (Consejo Superior de Investigaciones Científicas/Junta de Andalucía/Universidad Pablo de Olavide), Seville, Spain
| | - Mar García-Ferrés
- Centro Andaluz de Biología del Desarrollo (Consejo Superior de Investigaciones Científicas/Junta de Andalucía/Universidad Pablo de Olavide), Seville, Spain
| | - Carlos Sánchez-Higueras
- Centro Andaluz de Biología del Desarrollo (Consejo Superior de Investigaciones Científicas/Junta de Andalucía/Universidad Pablo de Olavide), Seville, Spain
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6
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Zappia MP, de Castro L, Ariss MM, Jefferson H, Islam AB, Frolov MV. A cell atlas of adult muscle precursors uncovers early events in fibre-type divergence in Drosophila. EMBO Rep 2020; 21:e49555. [PMID: 32815271 PMCID: PMC7534622 DOI: 10.15252/embr.201949555] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 07/12/2020] [Accepted: 07/24/2020] [Indexed: 12/31/2022] Open
Abstract
In Drosophila, the wing disc‐associated muscle precursor cells give rise to the fibrillar indirect flight muscles (IFM) and the tubular direct flight muscles (DFM). To understand early transcriptional events underlying this muscle diversification, we performed single‐cell RNA‐sequencing experiments and built a cell atlas of myoblasts associated with third instar larval wing disc. Our analysis identified distinct transcriptional signatures for IFM and DFM myoblasts that underlie the molecular basis of their divergence. The atlas further revealed various states of differentiation of myoblasts, thus illustrating previously unappreciated spatial and temporal heterogeneity among them. We identified and validated novel markers for both IFM and DFM myoblasts at various states of differentiation by immunofluorescence and genetic cell‐tracing experiments. Finally, we performed a systematic genetic screen using a panel of markers from the reference cell atlas as an entry point and found a novel gene, Amalgam which is functionally important in muscle development. Our work provides a framework for leveraging scRNA‐seq for gene discovery and details a strategy that can be applied to other scRNA‐seq datasets.
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Affiliation(s)
- Maria Paula Zappia
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Lucia de Castro
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Majd M Ariss
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Holly Jefferson
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Abul Bmmk Islam
- Department of Genetic Engineering and Biotechnology, University of Dhaka, Dhaka, Bangladesh
| | - Maxim V Frolov
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
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7
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Ng NHJ, Jasmen JB, Lim CS, Lau HH, Krishnan VG, Kadiwala J, Kulkarni RN, Ræder H, Vallier L, Hoon S, Teo AKK. HNF4A Haploinsufficiency in MODY1 Abrogates Liver and Pancreas Differentiation from Patient-Derived Induced Pluripotent Stem Cells. iScience 2019; 16:192-205. [PMID: 31195238 PMCID: PMC6562146 DOI: 10.1016/j.isci.2019.05.032] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 11/20/2018] [Accepted: 05/22/2019] [Indexed: 01/01/2023] Open
Abstract
Maturity-onset diabetes of the young 1 (MODY1) is a monogenic diabetes condition caused by heterozygous HNF4A mutations. We investigate how HNF4A haploinsufficiency from a MODY1/HNF4A mutation influences the development of foregut-derived liver and pancreatic cells through differentiation of human induced pluripotent stem cells from a MODY1 family down the foregut lineage. In MODY1-derived hepatopancreatic progenitors, which expressed reduced HNF4A levels and mislocalized HNF4A, foregut genes were downregulated, whereas hindgut-specifying HOX genes were upregulated. MODY1-derived hepatocyte-like cells were found to exhibit altered morphology. Hepatic and β cell gene signatures were also perturbed in MODY1-derived hepatocyte-like and β-like cells, respectively. As mutant HNF4A (p.Ile271fs) did not undergo complete nonsense-mediated decay or exert dominant negativity, HNF4A-mediated loss of function is likely due to impaired transcriptional activation of target genes. Our results suggest that in MODY1, liver and pancreas development is perturbed early on, contributing to altered hepatic proteins and β cell defects in patients. HNF4A is downregulated and predominantly mislocalized in the cytoplasm in MODY1 Foregut markers, pancreatic and hepatic genes, were downregulated in MODY1-HPPs A reciprocal upregulation of hindgut HOX genes was observed in MODY1-HPPs Mutant HNF4A resulted in loss of transcriptional activation of target genes
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Affiliation(s)
- Natasha Hui Jin Ng
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology, A*STAR, Singapore 138673, Singapore
| | - Joanita Binte Jasmen
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology, A*STAR, Singapore 138673, Singapore
| | - Chang Siang Lim
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology, A*STAR, Singapore 138673, Singapore
| | - Hwee Hui Lau
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology, A*STAR, Singapore 138673, Singapore; School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | | | - Juned Kadiwala
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, Anne McLaren Laboratory, Department of Surgery, University of Cambridge, Cambridge CB2 0SZ, UK
| | - Rohit N Kulkarni
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Harvard Stem Cell Institute, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02215, USA
| | - Helge Ræder
- Department of Pediatrics, Haukeland University Hospital, 5021 Bergen, Norway; KG Jebsen Center for Diabetes Research, Department of Clinical Science, Faculty of Medicine, University of Bergen, 5020 Bergen, Norway
| | - Ludovic Vallier
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, Anne McLaren Laboratory, Department of Surgery, University of Cambridge, Cambridge CB2 0SZ, UK; Wellcome Trust Sanger Institute, Hinxton CB10 1SA, UK
| | - Shawn Hoon
- Molecular Engineering Lab, A*STAR, Singapore 138673, Singapore
| | - Adrian Kee Keong Teo
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology, A*STAR, Singapore 138673, Singapore; School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore; Department of Biochemistry and Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore.
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8
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Shen Y, Wang L, Hirose S, Zhou Z, Liu Q. The transcriptional factor Apt regulates neuroblast differentiation through activating CycE expression. Biochem Biophys Res Commun 2018; 499:889-894. [PMID: 29625112 DOI: 10.1016/j.bbrc.2018.04.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 04/02/2018] [Indexed: 02/07/2023]
Abstract
In Drosophila, the thoracic neuroblast 6-4 (NB6-4T) divides asymmetrically into a glial precursor and a neuronal precursor, while the abdominal neuroblast 6-4 (NB6-4A) divides symmetrically to produce two glial cells. The underlying mechanism by which NB6-4T and NB6-4A undergo distinct differentiation is still elusive. Here, we find that the transcription factor Apontic (Apt) exclusively expresses in NB6-4T cells and is involved in regulating NB6-4T differentiation. Loss of Apt results in neuronal precursor loss. Epistasis analysis shows that Apt controls NB6-4T differentiation through activating CycE expression. On the other hand, Gcm suppresses Apt expression in the NB6-4A cell, thus inhibiting CycE expression. Taken together, our findings reveal a Gcm-Apt-CycE axis that regulates neuroblast and glia cell differentiation.
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Affiliation(s)
- Yang Shen
- College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong, 271018, China
| | - Luwei Wang
- College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong, 271018, China
| | - Susumu Hirose
- Department of Developmental Genetics, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
| | - Zizhang Zhou
- College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong, 271018, China.
| | - Qingxin Liu
- College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong, 271018, China.
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Rickert C, Lüer K, Vef O, Technau GM. Progressive derivation of serially homologous neuroblast lineages in the gnathal CNS of Drosophila. PLoS One 2018; 13:e0191453. [PMID: 29415052 PMCID: PMC5802887 DOI: 10.1371/journal.pone.0191453] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 01/04/2018] [Indexed: 11/18/2022] Open
Abstract
Along the anterior-posterior axis the central nervous system is subdivided into segmental units (neuromeres) the composition of which is adapted to their region-specific functional requirements. In Drosophila melanogaster each neuromere is formed by a specific set of identified neural stem cells (neuroblasts, NBs). In the thoracic and anterior abdominal region of the embryonic ventral nerve cord segmental sets of NBs resemble the ground state (2nd thoracic segment, which does not require input of homeotic genes), and serial (segmental) homologs generate similar types of lineages. The three gnathal head segments form a transitional zone between the brain and the ventral nerve cord. It has been shown recently that although all NBs of this zone are serial homologs of NBs in more posterior segments, they progressively differ from the ground state in anterior direction (labial > maxillary > mandibular segment) with regard to numbers and expression profiles. To study the consequences of their derived characters we traced the embryonic lineages of gnathal NBs using the Flybow and DiI-labelling techniques. For a number of clonal types serial homology is rather clearly reflected by their morphology (location and projection patterns) and cell specific markers, despite of reproducible segment-specific differences. However, many lineages, particularly in the mandibular segment, show a degree of derivation that impedes their assignment to ground state serial homologs. These findings demonstrate that differences in gene expression profiles of gnathal NBs go along with anteriorly directed progressive derivation in the composition of their lineages. Furthermore, lineage sizes decrease from labial to mandibular segments, which in concert with decreasing NB-numbers lead to reduced volumes of gnathal neuromeres, most significantly in the mandibular segment.
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Affiliation(s)
- Christof Rickert
- Institute of Developmental Biology and Neurobiology, University of Mainz, J.-J.-Becherweg 32,Mainz, Germany
- * E-mail: (CR); (GMT)
| | - Karin Lüer
- Institute of Developmental Biology and Neurobiology, University of Mainz, J.-J.-Becherweg 32,Mainz, Germany
| | - Olaf Vef
- Institute of Developmental Biology and Neurobiology, University of Mainz, J.-J.-Becherweg 32,Mainz, Germany
| | - Gerhard M. Technau
- Institute of Developmental Biology and Neurobiology, University of Mainz, J.-J.-Becherweg 32,Mainz, Germany
- * E-mail: (CR); (GMT)
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10
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Monedero Cobeta I, Salmani BY, Thor S. Anterior-Posterior Gradient in Neural Stem and Daughter Cell Proliferation Governed by Spatial and Temporal Hox Control. Curr Biol 2017; 27:1161-1172. [PMID: 28392108 DOI: 10.1016/j.cub.2017.03.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 02/09/2017] [Accepted: 03/10/2017] [Indexed: 01/16/2023]
Abstract
A readily evident feature of animal central nervous systems (CNSs), apparent in all vertebrates and many invertebrates alike, is its "wedge-like" appearance, with more cells generated in anterior than posterior regions. This wedge could conceivably be established by an antero-posterior (A-P) gradient in the number of neural progenitor cells, their proliferation behaviors, and/or programmed cell death (PCD). However, the contribution of each of these mechanisms, and the underlying genetic programs, are not well understood. Building upon recent progress in the Drosophila melanogaster (Drosophila) ventral nerve cord (VNC), we address these issues in a comprehensive manner. We find that, although PCD plays a role in controlling cell numbers along the A-P axis, the main driver of the wedge is a gradient of daughter proliferation, with divisions directly generating neurons (type 0) being more prevalent posteriorly and dividing daughters (type I) more prevalent anteriorly. In addition, neural progenitor (NB) cell-cycle exit occurs earlier posteriorly. The gradient of type I > 0 daughter proliferation switch and NB exit combine to generate radically different average lineage sizes along the A-P axis, differing by more than 3-fold in cell number. We find that the Hox homeotic genes, expressed in overlapping A-P gradients and with a late temporal onset in NBs, trigger the type I > 0 daughter proliferation switch and NB exit. Given the highly evolutionarily conserved expression of overlapping Hox homeotic genes in the CNS, our results point to a common mechanism for generating the CNS wedge.
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Affiliation(s)
- Ignacio Monedero Cobeta
- Department of Clinical and Experimental Medicine, Linkoping University, 58185 Linkoping, Sweden
| | | | - Stefan Thor
- Department of Clinical and Experimental Medicine, Linkoping University, 58185 Linkoping, Sweden.
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Hessinger C, Technau GM, Rogulja-Ortmann A. The Drosophila Hox gene Ultrabithorax acts in both muscles and motoneurons to orchestrate formation of specific neuromuscular connections. Development 2016; 144:139-150. [PMID: 27913640 PMCID: PMC5278631 DOI: 10.1242/dev.143875] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 11/17/2016] [Indexed: 12/29/2022]
Abstract
Hox genes are known to specify motoneuron pools in the developing vertebrate spinal cord and to control motoneuronal targeting in several species. However, the mechanisms controlling axial diversification of muscle innervation patterns are still largely unknown. We present data showing that the Drosophila Hox gene Ultrabithorax (Ubx) acts in the late embryo to establish target specificity of ventrally projecting RP motoneurons. In abdominal segments A2 to A7, RP motoneurons innervate the ventrolateral muscles VL1-4, with VL1 and VL2 being innervated in a Wnt4-dependent manner. In Ubx mutants, these motoneurons fail to make correct contacts with muscle VL1, a phenotype partially resembling that of the Wnt4 mutant. We show that Ubx regulates expression of Wnt4 in muscle VL2 and that it interacts with the Wnt4 response pathway in the respective motoneurons. Ubx thus orchestrates the interaction between two cell types, muscles and motoneurons, to regulate establishment of the ventrolateral neuromuscular network. Summary: Ultrabithorax controls correct innervation of ventrolateral muscles by coordinating Wnt4 ligand expression in muscles with the signalling pathway response in motoneurons.
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