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Chowdhury R, Roure A, le Pétillon Y, Mayeur H, Daric V, Darras S. Highly distinct genetic programs for peripheral nervous system formation in chordates. BMC Biol 2022; 20:152. [PMID: 35761237 PMCID: PMC9238270 DOI: 10.1186/s12915-022-01355-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 06/20/2022] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
Vertebrates develop their peripheral nervous system (PNS) from transient unique embryonic structures, the neural crest, and the ectodermal placodes that are located at the border of the forming central nervous system. By contrast, in the invertebrate chordates, amphioxus and ascidians, a large part of the PNS originates at the opposite of the embryo, in the ventral ectoderm. In both groups, a biphasic mechanism regulates ventral PNS formation: high BMP levels specify a neurogenic territory within which glutamatergic epidermal sensory neuron formation is controlled by the Notch pathway. Given these similarities and the phylogenetic relationships within chordates, it is likely that ventral PNS is an ancestral feature in chordates and that it has been lost in vertebrates.
Results
In order to get insights into the molecular control of ventral PNS formation and to test the hypothesis of their homology and potential contribution to the emergence of vertebrate PNS, we undertook a close comparison of ventral PNS formation in the ascidian Phallusia mammillata and the amphioxus Branchiostoma lanceolatum. Using timed RNA-seq series, we identified novel markers of the ventral PNS during different phases of its development in both species. By extensively determining the expression of paralogous and orthologous genes, we observed that only a minority of genes have a shared expression in the ventral PNS. However, a large fraction of ventral PNS orthologous genes are expressed in the dorsally forming PNS of vertebrates.
Conclusions
Our work has significantly increased the molecular characterization of ventral PNS formation in invertebrate chordates. The low observed conservation of gene expression in the ventral PNS suggests that the amphioxus and ascidian ventral PNS are either not homologous, or alternatively extensive drift has occurred in their regulatory mechanisms following a long period (600 My) of separate evolution and accelerated evolution in the ascidian lineage. The homology to genes expressed in the dorsally forming PNS of vertebrates suggests that ancestral sensory neurons gene networks have been redeployed in vertebrates.
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Kaufman ML, Goodson NB, Park KU, Schwanke M, Office E, Schneider SR, Abraham J, Hensley A, Jones KL, Brzezinski JA. Initiation of Otx2 expression in the developing mouse retina requires a unique enhancer and either Ascl1 or Neurog2 activity. Development 2021; 148:dev199399. [PMID: 34143204 PMCID: PMC8254865 DOI: 10.1242/dev.199399] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 05/10/2021] [Indexed: 11/20/2022]
Abstract
During retinal development, a large subset of progenitors upregulates the transcription factor Otx2, which is required for photoreceptor and bipolar cell formation. How these retinal progenitor cells initially activate Otx2 expression is unclear. To address this, we investigated the cis-regulatory network that controls Otx2 expression in mice. We identified a minimal enhancer element, DHS-4D, that drove expression in newly formed OTX2+ cells. CRISPR/Cas9-mediated deletion of DHS-4D reduced OTX2 expression, but this effect was diminished in postnatal development. Systematic mutagenesis of the enhancer revealed that three basic helix-loop-helix (bHLH) transcription factor-binding sites were required for its activity. Single cell RNA-sequencing of nascent Otx2+ cells identified the bHLH factors Ascl1 and Neurog2 as candidate regulators. CRISPR/Cas9 targeting of these factors showed that only the simultaneous loss of Ascl1 and Neurog2 prevented OTX2 expression. Our findings suggest that Ascl1 and Neurog2 act either redundantly or in a compensatory fashion to activate the DHS-4D enhancer and Otx2 expression. We observed redundancy or compensation at both the transcriptional and enhancer utilization levels, suggesting that the mechanisms governing Otx2 regulation in the retina are flexible and robust.
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Affiliation(s)
- Michael L. Kaufman
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Noah B. Goodson
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Ko Uoon Park
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Michael Schwanke
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Emma Office
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Sophia R. Schneider
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Joy Abraham
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Austin Hensley
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Kenneth L. Jones
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Joseph A. Brzezinski
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
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Xu B, Tang X, Jin M, Zhang H, Du L, Yu S, He J. Unifying developmental programs for embryonic and postembryonic neurogenesis in the zebrafish retina. Development 2020; 147:dev.185660. [PMID: 32467236 DOI: 10.1242/dev.185660] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Accepted: 05/13/2020] [Indexed: 01/14/2023]
Abstract
The zebrafish retina grows for a lifetime. Whether embryonic and postembryonic retinogenesis conform to the same developmental program is an outstanding question that remains under debate. Using single-cell RNA sequencing of ∼20,000 cells of the developing zebrafish retina at four different stages, we identified seven distinct developmental states. Each state explicitly expresses a gene set. Disruption of individual state-specific marker genes results in various defects ranging from small eyes to the loss of distinct retinal cell types. Using a similar approach, we further characterized the developmental states of postembryonic retinal stem cells (RSCs) and their progeny in the ciliary marginal zone. Expression pattern analysis of state-specific marker genes showed that the developmental states of postembryonic RSCs largely recapitulated those of their embryonic counterparts, except for some differences in rod photoreceptor genesis. Thus, our findings reveal the unifying developmental program used by the embryonic and postembryonic retinogenesis in zebrafish.
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Affiliation(s)
- Baijie Xu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China.,University of Chinese Academy of Sciences, Beijing 100049, China.,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Xia Tang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China .,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Mengmeng Jin
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China.,University of Chinese Academy of Sciences, Beijing 100049, China.,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Hui Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China.,University of Chinese Academy of Sciences, Beijing 100049, China.,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Lei Du
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China.,University of Chinese Academy of Sciences, Beijing 100049, China.,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Shuguang Yu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China.,University of Chinese Academy of Sciences, Beijing 100049, China.,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Jie He
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China .,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
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Patoori S, Jean-Charles N, Gopal A, Sulaiman S, Gopal S, Wang B, Souferi B, Emerson MM. Cis-regulatory analysis of Onecut1 expression in fate-restricted retinal progenitor cells. Neural Dev 2020; 15:5. [PMID: 32192535 PMCID: PMC7082998 DOI: 10.1186/s13064-020-00142-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 02/27/2020] [Indexed: 01/03/2023] Open
Abstract
Background The vertebrate retina consists of six major classes of neuronal cells. During development, these cells are generated from a pool of multipotent retinal progenitor cells (RPCs) that express the gene Vsx2. Fate-restricted RPCs have recently been identified, with limited mitotic potential and cell fate possibilities compared to multipotent RPCs. One population of fate-restricted RPCs, marked by activity of the regulatory element ThrbCRM1, gives rise to both cone photoreceptors and horizontal cells. These cells do not express Vsx2, but co-express the transcription factors (TFs) Onecut1 and Otx2, which bind to ThrbCRM1. The components of the gene regulatory networks that control the transition from multipotent to fate-restricted gene expression are not known. This work aims to identify and evaluate cis-regulatory elements proximal to Onecut1 to identify the gene regulatory networks involved in RPC fate-restriction. Method We identified regulatory elements through ATAC-seq and conservation, followed by reporter assays to screen for activity based on temporal and spatial criteria. The regulatory elements of interest were subject to deletion and mutation analysis to identify functional sequences and evaluated by quantitative flow cytometry assays. Finally, we combined the enhancer::reporter assays with candidate TF overexpression to evaluate the relationship between the TFs, the enhancers, and early vertebrate retinal development. Statistical tests included ANOVA, Kruskal-Wallis, or unpaired t-tests. Results Two regulatory elements, ECR9 and ECR65, were identified to be active in ThrbCRM1(+) restricted RPCs. Candidate bHLH binding sites were identified as critical sequences in both elements. Overexpression of candidate bHLH TFs revealed specific enhancer-bHLH interactions. Nhlh1 overexpression expanded ECR65 activity into the Vsx2(+) RPC population, and overexpression of NeuroD1/NeuroG2/NeuroD4 had a similar effect on ECR9. Furthermore, bHLHs that were able to activate ectopic ECR9 reporter were able to induce endogenous Otx2 expression. Conclusions This work reports a large-scale screen to identify spatiotemporally specific regulatory elements near the Onecut1 locus. These elements were used to identify distinct populations in the developing retina. In addition, fate-restricted regulatory elements responded differentially to bHLH factors, and suggest a role for retinal bHLHs upstream of the Otx2 and Onecut1 genes during the formation of restricted RPCs from multipotent RPCs.
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Affiliation(s)
- Sruti Patoori
- Biology PhD Program, The Graduate Center, The City University of New York, New York, NY, 10016, USA.,Department of Biology, The City College of New York, The City University of New York, New York, NY, 10031, USA
| | - Nathalie Jean-Charles
- Department of Biology, The City College of New York, The City University of New York, New York, NY, 10031, USA
| | - Ariana Gopal
- Department of Biology, The City College of New York, The City University of New York, New York, NY, 10031, USA
| | - Sacha Sulaiman
- Department of Biology, The City College of New York, The City University of New York, New York, NY, 10031, USA
| | - Sneha Gopal
- Department of Biology, The City College of New York, The City University of New York, New York, NY, 10031, USA.,Present Address: Doctoral program in Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Brian Wang
- Department of Biology, The City College of New York, The City University of New York, New York, NY, 10031, USA
| | - Benjamin Souferi
- Department of Biology, The City College of New York, The City University of New York, New York, NY, 10031, USA.,Present Address: Touro College of Osteopathic Medicine, New York, NY, 10027, USA
| | - Mark M Emerson
- Biology PhD Program, The Graduate Center, The City University of New York, New York, NY, 10016, USA. .,Department of Biology, The City College of New York, The City University of New York, New York, NY, 10031, USA. .,Biochemistry PhD Program, Graduate Center, City University of New York, New York, NY, 10016, USA.
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Kowalchuk AM, Maurer KA, Shoja-Taheri F, Brown NL. Requirements for Neurogenin2 during mouse postnatal retinal neurogenesis. Dev Biol 2018; 442:220-235. [PMID: 30048641 DOI: 10.1016/j.ydbio.2018.07.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 07/22/2018] [Accepted: 07/23/2018] [Indexed: 02/02/2023]
Abstract
During embryonic retinal development, the bHLH factor Neurog2 regulates the temporal progression of neurogenesis, but no role has been assigned for this gene in the postnatal retina. Using Neurog2 conditional mutants, we found that Neurog2 is necessary for the development of an early, embryonic cohort of rod photoreceptors, but also required by both a subset of cone bipolar subtypes, and rod bipolars. Using transcriptomics, we identified a subset of downregulated genes in P2 Neurog2 mutants, which act during rod differentiation, outer segment morphogenesis or visual processing. We also uncovered defects in neuronal cell culling, which suggests that the rod and bipolar cell phenotypes may arise via more complex mechanisms rather than a simple cell fate shift. However, given an overall phenotypic resemblance between Neurog2 and Blimp1 mutants, we explored the relationship between these two factors. We found that Blimp1 is downregulated between E12-birth in Neurog2 mutants, which probably reflects a dependence on Neurog2 in embryonic progenitor cells. Overall, we conclude that the Neurog2 gene is expressed and active prior to birth, but also exerts an influence on postnatal retinal neuron differentiation.
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Affiliation(s)
- Angelica M Kowalchuk
- Department of Cell Biology and Human Anatomy, University of California-Davis, Davis, CA 95616, USA
| | - Kate A Maurer
- Division of Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH 45229, USA
| | - Farnaz Shoja-Taheri
- Department of Cell Biology and Human Anatomy, University of California-Davis, Davis, CA 95616, USA
| | - Nadean L Brown
- Department of Cell Biology and Human Anatomy, University of California-Davis, Davis, CA 95616, USA; Division of Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH 45229, USA.
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