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Martini D, Digregorio M, Voto IAP, Morabito G, Degl'Innocenti A, Giudetti G, Giannaccini M, Andreazzoli M. Kdm7a expression is spatiotemporally regulated in developing Xenopus laevis embryos, and its overexpression influences late retinal development. Dev Dyn 2024; 253:508-518. [PMID: 37909656 DOI: 10.1002/dvdy.670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 09/26/2023] [Accepted: 10/02/2023] [Indexed: 11/03/2023] Open
Abstract
BACKGROUND Post-translational histone modifications are among the most common epigenetic modifications that orchestrate gene expression, playing a pivotal role during embryonic development and in various pathological conditions. Among histone lysine demethylases, KDM7A, also known as KIAA1718 or JHDM1D, catalyzes the demethylation of H3K9me1/2 and H3K27me1/2, leading to transcriptional regulation. Previous data suggest that KDM7A plays a central role in several biological processes, including cell proliferation, commitment, differentiation, apoptosis, and maintenance. However, information on the expression pattern of KDM7A in whole organisms is limited, and its functional role is still unclear. RESULTS In Xenopus development, kdm7a is expressed early, undergoing spatiotemporal regulation in various organs and tissues, including the central nervous system and the eye. Focusing on retinal development, we found that kdm7a overexpression does not affect the expression of genes critically involved in early neural development and eye-field specification, whereas unbalances the distribution of neural cell subtypes in the mature retina by disfavoring the development of ganglion cells while promoting that of horizontal cells. CONCLUSIONS Kdm7a is dynamically expressed during embryonic development, and its overexpression influences late retinal development, suggesting a potential involvement in the molecular machinery regulating the spatiotemporally ordered generation of retinal neuronal subtypes.
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Rath MF. Homeobox gene-encoded transcription factors in development and mature circadian function of the rodent pineal gland. J Pineal Res 2024; 76:e12950. [PMID: 38558122 DOI: 10.1111/jpi.12950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 02/15/2024] [Accepted: 03/11/2024] [Indexed: 04/04/2024]
Abstract
Homeobox genes encode transcription factors that are widely known to control developmental processes. This is also the case in the pineal gland, a neuroendocrine brain structure devoted to nighttime synthesis of the hormone melatonin. Thus, in accordance with high prenatal gene expression, knockout studies have identified a specific set of homeobox genes that are essential for development of the pineal gland. However, as a special feature of the pineal gland, homeobox gene expression persists into adulthood, and gene product abundance exhibits 24 h circadian rhythms. Recent lines of evidence show that some homeobox genes even control expression of enzymes catalyzing melatonin synthesis. We here review current knowledge of homeobox genes in the rodent pineal gland and suggest a model for dual functions of homeobox gene-encoded transcription factors in developmental and circadian mature neuroendocrine function.
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Affiliation(s)
- Martin F Rath
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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3
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Carstensen MB, Medvetzky A, Weinberger A, Driever W, Gothilf Y, Rath MF. Genetic ablation of the Bsx homeodomain transcription factor in zebrafish: Impact on mature pineal gland morphology and circadian behavior. J Pineal Res 2022; 72:e12795. [PMID: 35249239 PMCID: PMC9285933 DOI: 10.1111/jpi.12795] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/01/2022] [Accepted: 03/02/2022] [Indexed: 11/30/2022]
Abstract
The pineal gland is a neuroendocrine structure in the brain, which produces and secretes the hormone melatonin at nighttime and is considered a key element in the circadian clock system. Early morphogenesis of the gland is controlled by a number of transcription factors, some of which remain active in adult life. One of these is the brain-specific homeobox (Bsx), a highly conserved homeodomain transcription factor with a developmental role in the pineal gland of several species, including zebrafish, and regulatory roles in mature pinealocytes of the rat. To determine the role of Bsx in circadian biology, we here examined the effects of a bsx loss-of-function mutation on the pineal gland in adult zebrafish and on behavioral circadian rhythms in larvae. In pineal cell type-specific Gfp/Egfp reporter zebrafish lines, we did not detect fluorescence signals in the pineal area of homozygous (bsx-/- ) mutants. Interestingly, a nonpigmented area on the dorsal surface of the head above the gland, known as the pineal window, was pigmented in the homozygous mutants. Furthermore, a structure corresponding to the pineal gland was not detectable in the midline of the adult brain in histological sections analyzed by Nissl staining and S-antigen immunohistochemistry. Moreover, the levels of pineal transcripts were greatly reduced in bsx-/- mutants, as revealed by quantitative real-time polymerase chain reaction analysis. Notably, analysis of locomotor activity at the larval stage revealed altered circadian rhythmicity in the bsx mutants with periods and phases similar to wildtype, but severely reduced amplitudes in locomotor activity patterns. Thus, Bsx is essential for full development of the pineal gland, with its absence resulting in a phenotype of morphological pineal gland ablation and disrupted circadian behavior.
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Affiliation(s)
- Mikkel Bloss Carstensen
- Department of Neuroscience, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
- School of Neurobiology, Biochemistry and Biophysics, Faculty of Life SciencesTel Aviv UniversityTel AvivIsrael
| | - Adar Medvetzky
- School of Neurobiology, Biochemistry and Biophysics, Faculty of Life SciencesTel Aviv UniversityTel AvivIsrael
| | - Alon Weinberger
- School of Neurobiology, Biochemistry and Biophysics, Faculty of Life SciencesTel Aviv UniversityTel AvivIsrael
| | - Wolfgang Driever
- Developmental Biology, Institute Biology, Faculty of BiologyAlbert Ludwig University of FreiburgFreiburgGermany
| | - Yoav Gothilf
- School of Neurobiology, Biochemistry and Biophysics, Faculty of Life SciencesTel Aviv UniversityTel AvivIsrael
- Sagol School of NeuroscienceTel Aviv UniversityTel AvivIsrael
| | - Martin Fredensborg Rath
- Department of Neuroscience, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
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4
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Bertolesi GE, Debnath N, Malik HR, Man LLH, McFarlane S. Type II Opsins in the Eye, the Pineal Complex and the Skin of Xenopus laevis: Using Changes in Skin Pigmentation as a Readout of Visual and Circadian Activity. Front Neuroanat 2022; 15:784478. [PMID: 35126061 PMCID: PMC8814574 DOI: 10.3389/fnana.2021.784478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/13/2021] [Indexed: 01/17/2023] Open
Abstract
The eye, the pineal complex and the skin are important photosensitive organs. The African clawed frog, Xenopus laevis, senses light from the environment and adjusts skin color accordingly. For example, light reflected from the surface induces camouflage through background adaptation while light from above produces circadian variation in skin pigmentation. During embryogenesis, background adaptation, and circadian skin variation are segregated responses regulated by the secretion of α-melanocyte-stimulating hormone (α-MSH) and melatonin through the photosensitivity of the eye and pineal complex, respectively. Changes in the color of skin pigmentation have been used as a readout of biochemical and physiological processes since the initial purification of pineal melatonin from pigs, and more recently have been employed to better understand the neuroendocrine circuit that regulates background adaptation. The identification of 37 type II opsin genes in the genome of the allotetraploid X. laevis, combined with analysis of their expression in the eye, pineal complex and skin, is contributing to the elucidation of the role of opsins in the different photosensitive organs, but also brings new questions and challenges. In this review, we analyze new findings regarding the anatomical localization and functions of type II opsins in sensing light. The contribution of X. laevis in revealing the neuroendocrine circuits that regulate background adaptation and circadian light variation through changes in skin pigmentation is discussed. Finally, the presence of opsins in X. laevis skin melanophores is presented and compared with the secretory melanocytes of birds and mammals.
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Affiliation(s)
- Gabriel E. Bertolesi
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute and Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB, Canada
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5
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Homola JJ, Loftin CS, Cammen KM, Helbing CC, Birol I, Schultz TF, Kinnison MT. Replicated Landscape Genomics Identifies Evidence of Local Adaptation to Urbanization in Wood Frogs. J Hered 2020; 110:707-719. [PMID: 31278891 PMCID: PMC6785938 DOI: 10.1093/jhered/esz041] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 06/28/2019] [Indexed: 12/20/2022] Open
Abstract
Native species that persist in urban environments may benefit from local adaptation to novel selection factors. We used double-digest restriction-side associated DNA (RAD) sequencing to evaluate shifts in genome-wide genetic diversity and investigate the presence of parallel evolution associated with urban-specific selection factors in wood frogs (Lithobates sylvaticus). Our replicated paired study design involved 12 individuals from each of 4 rural and urban populations to improve our confidence that detected signals of selection are indeed associated with urbanization. Genetic diversity measures were less for urban populations; however, the effect size was small, suggesting little biological consequence. Using an FST outlier approach, we identified 37 of 8344 genotyped single nucleotide polymorphisms with consistent evidence of directional selection across replicates. A genome-wide association study analysis detected modest support for an association between environment type and 12 of the 37 FST outlier loci. Discriminant analysis of principal components using the 37 FST outlier loci produced correct reassignment for 87.5% of rural samples and 93.8% of urban samples. Eighteen of the 37 FST outlier loci mapped to the American bullfrog (Rana [Lithobates] catesbeiana) genome, although none were in coding regions. This evidence of parallel evolution to urban environments provides a powerful example of the ability of urban landscapes to direct evolutionary processes.
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Affiliation(s)
- Jared J Homola
- School of Biology and Ecology, University of Maine, Orono, ME.,Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI
| | - Cynthia S Loftin
- the US Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME
| | | | - Caren C Helbing
- the Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
| | - Inanc Birol
- the Canada's Michael Smith Genome Sciences Centre, British Columbia Cancer Agency, Vancouver, BC, Canada
| | - Thomas F Schultz
- the Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University, Beaufort, NC
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6
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Schredelseker T, Veit F, Dorsky RI, Driever W. Bsx Is Essential for Differentiation of Multiple Neuromodulatory Cell Populations in the Secondary Prosencephalon. Front Neurosci 2020; 14:525. [PMID: 32581684 PMCID: PMC7290237 DOI: 10.3389/fnins.2020.00525] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 04/28/2020] [Indexed: 01/17/2023] Open
Abstract
The hypothalamus is characterized by great neuronal diversity, with many neuropeptides and other neuromodulators being expressed within its multiple anatomical domains. The regulatory networks directing hypothalamic development have been studied in detail, but, for many neuron types, control of differentiation is still not understood. The highly conserved Brain-specific homeobox (Bsx) transcription factor has previously been described in regulating Agrp and Npy expression in the hypothalamic arcuate nucleus (ARC) in mice. While Bsx is expressed in many more subregions of both tuberal and mamillary hypothalamus, the functions therein are not known. Using genetic analyses in zebrafish, we show that most bsx expression domains are dependent on Nkx2.1 and Nkx2.4 homeodomain transcription factors, while a subset depends on Otp. We show that the anatomical pattern of the ventral forebrain appears normal in bsx mutants, but that Bsx is necessary for the expression of many neuropeptide encoding genes, including agrp, penka, vip, trh, npb, and nts, in distinct hypothalamic anatomical domains. We also found Bsx to be critical for normal expression of two Crh family members, crhb and uts1, as well as crhbp, in the hypothalamus and the telencephalic septal region. Furthermore, we demonstrate a crucial role for Bsx in serotonergic, histaminergic and nitrergic neuron development in the hypothalamus. We conclude that Bsx is critical for the terminal differentiation of multiple neuromodulatory cell types in the forebrain.
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Affiliation(s)
- Theresa Schredelseker
- Developmental Biology, Institute Biology 1, Faculty of Biology, Albert Ludwig University of Freiburg, Freiburg im Breisgau, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg im Breisgau, Germany.,CIBSS - Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg im Breisgau, Germany
| | - Florian Veit
- Developmental Biology, Institute Biology 1, Faculty of Biology, Albert Ludwig University of Freiburg, Freiburg im Breisgau, Germany
| | - Richard I Dorsky
- Department of Neurobiology & Anatomy, University of Utah, Salt Lake City, UT, United States
| | - Wolfgang Driever
- Developmental Biology, Institute Biology 1, Faculty of Biology, Albert Ludwig University of Freiburg, Freiburg im Breisgau, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg im Breisgau, Germany.,CIBSS - Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg im Breisgau, Germany
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7
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Carstensen MB, Hertz H, Bering T, Møller M, Rohde K, Klein DC, Coon SL, Rath MF. Circadian regulation and molecular role of the Bsx homeobox gene in the adult pineal gland. J Pineal Res 2020; 68:e12629. [PMID: 31808568 PMCID: PMC7122731 DOI: 10.1111/jpi.12629] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 11/29/2019] [Accepted: 11/30/2019] [Indexed: 11/28/2022]
Abstract
The pineal gland is a neuroendocrine organ responsible for production of the nocturnal hormone melatonin. A specific set of homeobox gene-encoded transcription factors govern pineal development, and some are expressed in adulthood. The brain-specific homeobox gene (Bsx) falls into both categories. We here examined regulation and function of Bsx in the mature pineal gland of the rat. We report that Bsx is expressed from prenatal stages into adulthood, where Bsx transcripts are localized in the melatonin-synthesizing pinealocytes, as revealed by RNAscope in situ hybridization. Bsx transcripts were also detected in the adult human pineal gland. In the rat pineal gland, Bsx was found to exhibit a 10-fold circadian rhythm with a peak at night. By combining in vivo adrenergic stimulation and surgical denervation of the gland in the rat with in vitro stimulation and transcriptional inhibition in cultured pinealocytes, we show that rhythmic expression of Bsx is controlled at the transcriptional level by the sympathetic neural input to the gland acting via adrenergic stimulation with cyclic AMP as a second messenger. siRNA-mediated knockdown (>80% reduction) in pinealocyte cultures revealed Bsx to be a negative regulator of other pineal homeobox genes, including paired box 4 (Pax4), but no effect on genes encoding melatonin-synthesizing enzymes was detected. RNA sequencing analysis performed on siRNA-treated pinealocytes further revealed that downstream target genes of Bsx are mainly involved in developmental processes. Thus, rhythmic Bsx expression seems to govern other developmental regulators in the mature pineal gland.
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Affiliation(s)
- Mikkel B Carstensen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Henrik Hertz
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tenna Bering
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Morten Møller
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kristian Rohde
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - David C Klein
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Steven L Coon
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Martin F Rath
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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8
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Staudt N, Giger FA, Fielding T, Hutt JA, Foucher I, Snowden V, Hellich A, Kiecker C, Houart C. Pineal progenitors originate from a non-neural territory limited by FGF signalling. Development 2019; 146:dev.171405. [PMID: 31754007 PMCID: PMC7375831 DOI: 10.1242/dev.171405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 10/30/2019] [Indexed: 01/10/2023]
Abstract
The embryonic development of the pineal organ, a neuroendocrine gland on top of the diencephalon, remains enigmatic. Classic fate-mapping studies suggested that pineal progenitors originate from the lateral border of the anterior neural plate. We show here, using gene expression and fate mapping/lineage tracing in zebrafish, that pineal progenitors originate, at least in part, from the non-neural ectoderm. Gene expression in chick indicates that this non-neural origin of pineal progenitors is conserved in amniotes. Genetic repression of placodal, but not neural crest, cell fate results in pineal hypoplasia in zebrafish, while mis-expression of transcription factors known to specify placodal identity during gastrulation promotes the formation of ectopic pineal progenitors. We also demonstrate that fibroblast growth factors (FGFs) position the pineal progenitor domain within the non-neural border by repressing pineal fate and that the Otx transcription factors promote pinealogenesis by inhibiting this FGF activity. The non-neural origin of the pineal organ reveals an underlying similarity in the formation of the pineal and pituitary glands, and suggests that all CNS neuroendocrine organs may require a non-neural contribution to form neurosecretory cells. Highlighted Article: Gene expression and fate mapping/lineage tracing in zebrafish reveals that the pineal organ develops from the non-neural pre-placodal ectoderm under the control of FGF signalling.
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Affiliation(s)
- Nicole Staudt
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
| | - Florence A Giger
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
| | - Triona Fielding
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
| | - James A Hutt
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
| | - Isabelle Foucher
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
| | - Vicky Snowden
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
| | - Agathe Hellich
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
| | - Clemens Kiecker
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
| | - Corinne Houart
- Department for Developmental Neurobiology, Guy's Hospital Campus, King's College London, London SE1 1UL, UK
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9
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Mano H, Asaoka Y, Kojima D, Fukada Y. Brain-specific homeobox Bsx specifies identity of pineal gland between serially homologous photoreceptive organs in zebrafish. Commun Biol 2019; 2:364. [PMID: 31602413 PMCID: PMC6779754 DOI: 10.1038/s42003-019-0613-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 09/16/2019] [Indexed: 01/11/2023] Open
Abstract
The pineal gland functioning as a photoreceptive organ in non-mammalian species is a serial homolog of the retina. Here we found that Brain-specific homeobox (Bsx) is a key regulator conferring individuality on the pineal gland between the two serially homologous photoreceptive organs in zebrafish. Bsx knock-down impaired the pineal development with reduced expression of exorh, the pineal-specific gene responsible for the photoreception, whereas it induced ectopic expression of rho, a retina-specific gene, in the pineal gland. Bsx remarkably transactivated the exorh promoter in combination with Otx5, but not with Crx, through its binding to distinct subtypes of PIRE, a DNA cis-element driving Crx/Otx-dependent pineal-specific gene expression. These results demonstrate that the identity of pineal photoreceptive neurons is determined by the combinatorial code of Bsx and Otx5, the former confers the pineal specificity at the tissue level and the latter determines the photoreceptor specificity at the cellular level.
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Affiliation(s)
- Hiroaki Mano
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan
| | - Yoichi Asaoka
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan
| | - Daisuke Kojima
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan
| | - Yoshitaka Fukada
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan
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10
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Schredelseker T, Driever W. Bsx controls pineal complex development. Development 2018; 145:dev.163477. [DOI: 10.1242/dev.163477] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 06/08/2018] [Indexed: 12/18/2022]
Abstract
Neuroendocrine cells in the pineal gland release melatonin during the night and in teleosts are directly photoreceptive. During development of the pineal complex, a small number of cells migrate leftward away from the pineal anlage to form the parapineal cell cluster, a process which is crucial for asymmetrical development of the bilateral habenular nuclei. Here we show that, throughout zebrafish embryonic development, the brain-specific homeobox (bsx) gene is expressed in all cell types of the pineal complex. We identified Bmp and Noto/Flh as major regulators of bsx expression in the pineal complex. Upon loss of Bsx through the generation of a targeted mutation, embryos fail to form a parapineal organ and develop right-isomerized habenulae. Crucial enzymes in the melatonin biosynthesis pathway are not expressed, suggesting absence of melatonin from the pineal gland of bsx mutants. Several genes involved in rod-like or cone-like phototransduction are also abnormally expressed, indicating that Bsx plays a pivotal role in differentiation of multiple cell types in the zebrafish pineal complex.
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Affiliation(s)
- Theresa Schredelseker
- Developmental Biology, Institute Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, Hauptstrasse 1, 79104 Freiburg, Germany
- BIOSS - Centre for Biological Signalling Studies, Albertstrasse 19, 79104 Freiburg, Germany
| | - Wolfgang Driever
- Developmental Biology, Institute Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, Hauptstrasse 1, 79104 Freiburg, Germany
- BIOSS - Centre for Biological Signalling Studies, Albertstrasse 19, 79104 Freiburg, Germany
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11
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Giannaccini M, Giudetti G, Biasci D, Mariotti S, Martini D, Barsacchi G, Andreazzoli M. Brief report: Rx1 defines retinal precursor identity by repressing alternative fates through the activation of TLE2 and Hes4. Stem Cells 2015; 31:2842-7. [PMID: 24038725 DOI: 10.1002/stem.1530] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 07/13/2013] [Accepted: 07/22/2013] [Indexed: 12/25/2022]
Abstract
The molecular mechanisms underlying the acquisition of retinal precursor identity are scarcely defined. Although the homeobox gene Rx1 (also known as Rax) plays a major role in specifying retinal precursors and maintaining their multipotent state, the involved mechanisms remain to be largely deciphered. Here, following a highthroughput screen for genes regulated by Rx1, we found that this transcription factor specifies the fate of retinal progenitors by repressing genes normally activated in adjacent ectodermal territories. Unexpectedly, we also observed that Rx1, mainly through the activation of the transcriptional repressors TLE2 and Hes4, is necessary and sufficient to inhibit endomesodermal gene expression in retinal precursors of the eye field. In particular, Rx1 knockdown leads retinogenic blastomeres to adopt an endomesodermal fate, indicating a previously undescribed function for Rx1 in preventing the expression of endomesoderm determinants known to inhibit retinal fate. Altogether these data suggest that an essential requirement to establish a retinal precursor identity is the active inhibition of pathways leading to alternative fates.
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Affiliation(s)
- Martina Giannaccini
- Unità di Biologia Cellulare e dello Sviluppo, Dipartimento di Biologia, Università di Pisa, Pisa, Italy; Istituto di Scienze della Vita, Scuola Superiore Sant'Anna, Pisa, Italy
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12
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Giudetti G, Giannaccini M, Biasci D, Mariotti S, Degl'innocenti A, Perrotta M, Barsacchi G, Andreazzoli M. Characterization of the Rx1-dependent transcriptome during early retinal development. Dev Dyn 2014; 243:1352-61. [PMID: 24801179 DOI: 10.1002/dvdy.24145] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 04/29/2014] [Accepted: 05/04/2014] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND The transcription factor Rx1, also known as Rax, controls key properties of retinal precursors including migration behavior, proliferation, and maintenance of multipotency. However, Rx1 effector genes are largely unknown. RESULTS To identify genes controlled by Rx1 in early retinal precursors, we compared the transcriptome of Xenopus embryos overexpressing Rx1 to that of embryos in which Rx1 was knocked-down. In particular, we selected 52 genes coherently regulated, i.e., actived in Rx1 gain of function and repressed in Rx1 loss of function experiments, or vice versa. RT-qPCR and in situ hybridization confirmed the trend of regulation predicted by microarray data for the selected genes. Most of the genes upregulated by Rx1 are coexpressed with this transcription factor, while downregulated genes are either not expressed or expressed at very low levels in the early developing retina. Putative direct Rx1 target genes, activated by GR-Rx1 in the absence of protein synthesis, include Ephrin B1 and Sh2d3c, an interactor of ephrinB1 receptor, which represent candidate novel effectors for the migration promoting activity of Rx1. CONCLUSIONS This study identifies previously undescribed Rx1 regulated genes mainly involved in transcription regulation, cell migration/adhesion, and cell proliferation that contribute to delineate the molecular mechanisms underlying Rx1 activities.
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Affiliation(s)
- Guido Giudetti
- Unità di Biologia Cellulare e dello Sviluppo, Dipartimento di Biologia, Università di Pisa, Pisa, Italy
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13
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Brain-specific-homeobox is required for the specification of neuronal types in the Drosophila optic lobe. Dev Biol 2013; 377:90-9. [PMID: 23454478 DOI: 10.1016/j.ydbio.2013.02.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 02/15/2013] [Accepted: 02/17/2013] [Indexed: 12/17/2022]
Abstract
The Drosophila optic lobe comprises a wide variety of neurons forming laminar and columnar structures similar to the mammalian brain. The Drosophila optic lobe may provide an excellent model to investigate various processes of brain development. However, it is poorly understood how neuronal specification is regulated in the optic lobe to form a complicated structure. Here we show that the Brain-specific-homeobox (Bsh) protein, which is expressed in the lamina and medulla ganglia, is involved in specifying neuronal identity. Bsh is expressed in L4 and L5 lamina neurons and in Mi1 medulla neurons. Analyses of loss-of-function and gain-of-function clones suggest that Bsh is required and largely sufficient for Mi1 specification in the medulla and L4 specification in the lamina. Additionally, Bsh is at least required for L5 specification. In the absence of Bsh, L5 is transformed into glial cells.
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14
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Rath MF, Rohde K, Klein DC, Møller M. Homeobox genes in the rodent pineal gland: roles in development and phenotype maintenance. Neurochem Res 2012; 38:1100-12. [PMID: 23076630 DOI: 10.1007/s11064-012-0906-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 09/19/2012] [Accepted: 10/04/2012] [Indexed: 12/12/2022]
Abstract
The pineal gland is a neuroendocrine gland responsible for nocturnal synthesis of melatonin. During early development of the rodent pineal gland from the roof of the diencephalon, homeobox genes of the orthodenticle homeobox (Otx)- and paired box (Pax)-families are expressed and are essential for normal pineal development consistent with the well-established role that homeobox genes play in developmental processes. However, the pineal gland appears to be unusual because strong homeobox gene expression persists in the pineal gland of the adult brain. Accordingly, in addition to developmental functions, homeobox genes appear to be key regulators in postnatal phenotype maintenance in this tissue. In this paper, we review ontogenetic and phylogenetic aspects of pineal development and recent progress in understanding the involvement of homebox genes in rodent pineal development and adult function. A working model is proposed for understanding the sequential action of homeobox genes in controlling development and mature circadian function of the mammalian pinealocyte based on knowledge from detailed developmental and daily gene expression analyses in rats, the pineal phenotypes of homebox gene-deficient mice and studies on development of the retinal photoreceptor; the pinealocyte and retinal photoreceptor share features not seen in other tissues and are likely to have evolved from the same ancestral photodetector cell.
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Affiliation(s)
- Martin F Rath
- Department of Neuroscience and Pharmacology, Panum Institute 24.2, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, Copenhagen 2200, Denmark.
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Abstract
Long noncoding RNAs (lncRNAs) play a broad range of biological roles, including regulation of expression of genes and chromosomes. Here, we present evidence that lncRNAs are involved in vertebrate circadian biology. Differential night/day expression of 112 lncRNAs (0.3 to >50 kb) occurs in the rat pineal gland, which is the source of melatonin, the hormone of the night. Approximately one-half of these changes reflect nocturnal increases. Studies of eight lncRNAs with 2- to >100-fold daily rhythms indicate that, in most cases, the change results from neural stimulation from the central circadian oscillator in the suprachiasmatic nucleus (doubling time = 0.5-1.3 h). Light exposure at night rapidly reverses (halving time = 9-32 min) levels of some of these lncRNAs. Organ culture studies indicate that expression of these lncRNAs is regulated by norepinephrine acting through cAMP. These findings point to a dynamic role of lncRNAs in the circadian system.
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de Borsetti NH, Dean BJ, Bain EJ, Clanton JA, Taylor RW, Gamse JT. Light and melatonin schedule neuronal differentiation in the habenular nuclei. Dev Biol 2011; 358:251-61. [PMID: 21840306 DOI: 10.1016/j.ydbio.2011.07.038] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 07/26/2011] [Accepted: 07/28/2011] [Indexed: 01/16/2023]
Abstract
The formation of the embryonic brain requires the production, migration, and differentiation of neurons to be timely and coordinated. Coupling to the photoperiod could synchronize the development of neurons in the embryo. Here, we consider the effect of light and melatonin on the differentiation of embryonic neurons in zebrafish. We examine the formation of neurons in the habenular nuclei, a paired structure found near the dorsal surface of the brain adjacent to the pineal organ. Keeping embryos in constant darkness causes a temporary accumulation of habenular precursor cells, resulting in late differentiation and a long-lasting reduction in neuronal processes (neuropil). Because constant darkness delays the accumulation of the neurendocrine hormone melatonin in embryos, we looked for a link between melatonin signaling and habenular neurogenesis. A pharmacological block of melatonin receptors delays neurogenesis and reduces neuropil similarly to constant darkness, while addition of melatonin to embryos in constant darkness restores timely neurogenesis and neuropil. We conclude that light and melatonin schedule the differentiation of neurons and the formation of neural processes in the habenular nuclei.
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