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Paşcalău R, Badea TC. Signaling - transcription interactions in mouse retinal ganglion cells early axon pathfinding -a literature review. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1180142. [PMID: 38983012 PMCID: PMC11182120 DOI: 10.3389/fopht.2023.1180142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Accepted: 04/21/2023] [Indexed: 07/11/2024]
Abstract
Sending an axon out of the eye and into the target brain nuclei is the defining feature of retinal ganglion cells (RGCs). The literature on RGC axon pathfinding is vast, but it focuses mostly on decision making events such as midline crossing at the optic chiasm or retinotopic mapping at the target nuclei. In comparison, the exit of RGC axons out of the eye is much less explored. The first checkpoint on the RGC axons' path is the optic cup - optic stalk junction (OC-OS). OC-OS development and the exit of the RGC pioneer axons out of the eye are coordinated spatially and temporally. By the time the optic nerve head domain is specified, the optic fissure margins are in contact and the fusion process is ongoing, the first RGCs are born in its proximity and send pioneer axons in the optic stalk. RGC differentiation continues in centrifugal waves. Later born RGC axons fasciculate with the more mature axons. Growth cones at the end of the axons respond to guidance cues to adopt a centripetal direction, maintain nerve fiber layer restriction and to leave the optic cup. Although there is extensive information on OC-OS development, we still have important unanswered questions regarding its contribution to the exit of the RGC axons out of the eye. We are still to distinguish the morphogens of the OC-OS from the axon guidance molecules which are expressed in the same place at the same time. The early RGC transcription programs responsible for axon emergence and pathfinding are also unknown. This review summarizes the molecular mechanisms for early RGC axon guidance by contextualizing mouse knock-out studies on OC-OS development with the recent transcriptomic studies on developing RGCs in an attempt to contribute to the understanding of human optic nerve developmental anomalies. The published data summarized here suggests that the developing optic nerve head provides a physical channel (the closing optic fissure) as well as molecular guidance cues for the pioneer RGC axons to exit the eye.
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Affiliation(s)
- Raluca Paşcalău
- Research and Development Institute, Transilvania University of Braşov, Braşov, Romania
- Ophthalmology Clinic, Cluj County Emergency Hospital, Cluj-Napoca, Romania
| | - Tudor Constantin Badea
- Research and Development Institute, Transilvania University of Braşov, Braşov, Romania
- National Center for Brain Research, Institutul de Cercetări pentru Inteligență Artificială, Romanian Academy, Bucharest, Romania
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2
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Li X, Gordon PJ, Gaynes JA, Fuller AW, Ringuette R, Santiago CP, Wallace V, Blackshaw S, Li P, Levine EM. Lhx2 is a progenitor-intrinsic modulator of Sonic Hedgehog signaling during early retinal neurogenesis. eLife 2022; 11:e78342. [PMID: 36459481 PMCID: PMC9718532 DOI: 10.7554/elife.78342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 11/09/2022] [Indexed: 12/03/2022] Open
Abstract
An important question in organogenesis is how tissue-specific transcription factors interact with signaling pathways. In some cases, transcription factors define the context for how signaling pathways elicit tissue- or cell-specific responses, and in others, they influence signaling through transcriptional regulation of signaling components or accessory factors. We previously showed that during optic vesicle patterning, the Lim-homeodomain transcription factor Lhx2 has a contextual role by linking the Sonic Hedgehog (Shh) pathway to downstream targets without regulating the pathway itself. Here, we show that during early retinal neurogenesis in mice, Lhx2 is a multilevel regulator of Shh signaling. Specifically, Lhx2 acts cell autonomously to control the expression of pathway genes required for efficient activation and maintenance of signaling in retinal progenitor cells. The Shh co-receptors Cdon and Gas1 are candidate direct targets of Lhx2 that mediate pathway activation, whereas Lhx2 directly or indirectly promotes the expression of other pathway components important for activation and sustained signaling. We also provide genetic evidence suggesting that Lhx2 has a contextual role by linking the Shh pathway to downstream targets. Through these interactions, Lhx2 establishes the competence for Shh signaling in retinal progenitors and the context for the pathway to promote early retinal neurogenesis. The temporally distinct interactions between Lhx2 and the Shh pathway in retinal development illustrate how transcription factors and signaling pathways adapt to meet stage-dependent requirements of tissue formation.
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Affiliation(s)
- Xiaodong Li
- Vanderbilt Eye Institute, Vanderbilt University Medical CenterNashvilleUnited States
| | - Patrick J Gordon
- John A. Moran Eye Center, University of UtahSalt Lake CityUnited States
| | - John A Gaynes
- John A. Moran Eye Center, University of UtahSalt Lake CityUnited States
| | - Alexandra W Fuller
- Department of Cell and Developmental Biology, Vanderbilt UniversityNashvilleUnited States
| | - Randy Ringuette
- Cellular and Molecular Medicine, University of OttawaOttawaCanada
| | - Clayton P Santiago
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Valerie Wallace
- Donald K. Johnson Eye Institute, Krembil Research Institute, University Health NetworkTorontoCanada
| | - Seth Blackshaw
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Pulin Li
- Whitehead Institute of Biomedical Research, Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Edward M Levine
- Vanderbilt Eye Institute, Vanderbilt University Medical CenterNashvilleUnited States
- John A. Moran Eye Center, University of UtahSalt Lake CityUnited States
- Department of Cell and Developmental Biology, Vanderbilt UniversityNashvilleUnited States
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3
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Tian Q, Sun Y, Gao T, Li J, Hao Z, Fang H, Zhang S. TBX2/3 is required for regeneration of dorsal-ventral and medial-lateral polarity in planarians. J Cell Biochem 2021; 122:731-738. [PMID: 33586232 DOI: 10.1002/jcb.29905] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 11/24/2020] [Accepted: 01/21/2021] [Indexed: 12/24/2022]
Abstract
The molecular mechanisms responsible for axis establishment during non-embryonic processes remain elusive. The planarian flatworm is an ideal model organism to study body axis polarization and patterning in vivo. Here, we identified a homolog of the TBX2/3 in the planarian Dugesia japonica. RNA interference (RNAi) knockdown of TBX2/3 results in the ectopic formation of protrusions in the midline of the dorsal surface which shows an abnormal expression of midline and ventral cell markers. Additionally, the TBX2/3 RNAi animals also show the duplication of expression of the boundary marker at the lateral edge. Furthermore, TBX2/3 is expressed in muscle cells and co-expressed with bmp4. Inhibition of bone morphogenetic protein (BMP) signaling reduces the expression of TBX2/3 at the midline. These results suggest that TBX2/3 RNAi results in phenotypic characters caused by inhibition of the BMP signal, indicating that TBX2/3 is required for DV and ML patterning, and might be a downstream gene of BMP signaling.
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Affiliation(s)
- Qingnan Tian
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Yujia Sun
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Tingting Gao
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Jiaxin Li
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Zhitai Hao
- Department of Biochemistry and Molecular Pharmacology, School of Medicine, New York University, New York, USA
| | - Huimin Fang
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Shoutao Zhang
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China.,Henan Key Laboratory of Bioactive Macromolecules, Zhengzhou, Henan, China
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Cardozo MJ, Almuedo-Castillo M, Bovolenta P. Patterning the Vertebrate Retina with Morphogenetic Signaling Pathways. Neuroscientist 2019; 26:185-196. [PMID: 31509088 DOI: 10.1177/1073858419874016] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The primordium of the vertebrate eye is composed of a pseudostratified and apparently homogeneous neuroepithelium, which folds inward to generate a bilayered optic cup. During these early morphogenetic events, the optic vesicle is patterned along three different axes-proximo-distal, dorso-ventral, and naso-temporal-and three major domains: the neural retina, the retinal pigment epithelium (RPE), and the optic stalk. These fundamental steps that enable the subsequent development of a functional eye, entail the precise coordination among genetic programs. These programs are driven by the interplay of signaling pathways and transcription factors, which progressively dictate how each tissue should evolve. Here, we discuss the contribution of the Hh, Wnt, FGF, and BMP signaling pathways to the early patterning of the retina. Comparative studies in different vertebrate species have shown that their morphogenetic activity is repetitively used to orchestrate the progressive specification of the eye with evolutionary conserved mechanisms that have been adapted to match the specific need of a given species.
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Affiliation(s)
- Marcos J Cardozo
- Centro de Biología Molecular "Severo Ochoa," (CSIC/UAM), Madrid, Spain.,CIBERER, ISCIII, Madrid, Spain
| | | | - Paola Bovolenta
- Centro de Biología Molecular "Severo Ochoa," (CSIC/UAM), Madrid, Spain.,CIBERER, ISCIII, Madrid, Spain
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Lupu FI, Burnett JB, Eggenschwiler JT. Cell cycle-related kinase regulates mammalian eye development through positive and negative regulation of the Hedgehog pathway. Dev Biol 2017; 434:24-35. [PMID: 29166577 DOI: 10.1016/j.ydbio.2017.10.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 10/30/2017] [Accepted: 10/30/2017] [Indexed: 01/20/2023]
Abstract
Cell cycle-related kinase (CCRK) is a conserved regulator of ciliogenesis whose loss in mice leads to a wide range of developmental defects, including exencephaly, preaxial polydactyly, skeletal abnormalities, and microphthalmia. Here, we investigate the role of CCRK in mouse eye development. Ccrk mutants show dramatic patterning defects, with an expansion of the optic stalk domain into the optic cup, as well as an expansion of the retinal pigment epithelium (RPE) into neural retina (NR) territory. In addition, Ccrk mutants display a shortened optic stalk. These defects are associated with bimodal changes in Hedgehog (Hh) pathway activity within the eye, including the loss of proximal, high level responses but a gain in distal, low level responses. We simultaneously removed the Hh activator GLI2 in Ccrk mutants (Ccrk-/-;Gli2-/-), which resulted in rescue of optic cup patterning and exacerbation of optic stalk length defects. Next, we disrupted the Hh pathway antagonist GLI3 in mutants lacking CCRK (Ccrk-/-;Gli3-/-), which lead to even greater expansion of the RPE markers into the NR domain and a complete loss of NR specification within the optic cup. These results indicate that CCRK functions in eye development by both positively and negatively regulating the Hh pathway, and they reveal distinct requirements for Hh signaling in patterning and morphogenesis of the eyes.
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Affiliation(s)
- Floria I Lupu
- Department of Genetics, University of Georgia, Athens, GA 30602, USA
| | - Jacob B Burnett
- Department of Genetics, University of Georgia, Athens, GA 30602, USA
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Burnett JB, Lupu FI, Eggenschwiler JT. Proper ciliary assembly is critical for restricting Hedgehog signaling during early eye development in mice. Dev Biol 2017; 430:32-40. [PMID: 28778798 DOI: 10.1016/j.ydbio.2017.07.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 07/20/2017] [Accepted: 07/20/2017] [Indexed: 11/25/2022]
Abstract
Patterning of the vertebrate eye into optic stalk, retinal pigment epithelium (RPE) and neural retina (NR) territories relies on a number of signaling pathways, but how these signals are interpreted by optic progenitors is not well understood. The primary cilium is a microtubule-based organelle that is essential for Hedgehog (Hh) signaling, but it has also been implicated in the regulation of other signaling pathways. Here, we show that the optic primordium is ciliated during early eye development and that ciliogenesis is essential for proper patterning and morphogenesis of the mouse eye. Ift172 mutants fail to generate primary cilia and exhibit patterning defects that resemble those of Gli3 mutants, suggesting that cilia are required to restrict Hh activity during eye formation. Ift122 mutants, which produce cilia with abnormal morphology, generate optic vesicles that fail to invaginate to produce the optic cup. These mutants also lack formation of the lens, RPE and NR. Such phenotypic features are accompanied by strong, ectopic Hh pathway activity, evidenced by altered gene expression patterns. Removal of GLI2 from Ift122 mutants rescued several aspects of optic cup and lens morphogenesis as well as RPE and NR specification. Collectively, our data suggest that proper assembly of primary cilia is critical for restricting the Hedgehog pathway during eye formation in the mouse.
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Affiliation(s)
- Jacob B Burnett
- Department of Genetics, University of Georgia, Athens, GA 30602, United States
| | - Floria I Lupu
- Department of Genetics, University of Georgia, Athens, GA 30602, United States
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Sedykh I, Yoon B, Roberson L, Moskvin O, Dewey CN, Grinblat Y. Zebrafish zic2 controls formation of periocular neural crest and choroid fissure morphogenesis. Dev Biol 2017; 429:92-104. [PMID: 28689736 DOI: 10.1016/j.ydbio.2017.07.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/30/2017] [Accepted: 07/06/2017] [Indexed: 12/31/2022]
Abstract
The vertebrate retina develops in close proximity to the forebrain and neural crest-derived cartilages of the face and jaw. Coloboma, a congenital eye malformation, is associated with aberrant forebrain development (holoprosencephaly) and with craniofacial defects (frontonasal dysplasia) in humans, suggesting a critical role for cross-lineage interactions during retinal morphogenesis. ZIC2, a zinc-finger transcription factor, is linked to human holoprosencephaly. We have previously used morpholino assays to show zebrafish zic2 functions in the developing forebrain, retina and craniofacial cartilage. We now report that zebrafish with genetic lesions in zebrafish zic2 orthologs, zic2a and zic2b, develop with retinal coloboma and craniofacial anomalies. We demonstrate a requirement for zic2 in restricting pax2a expression and show evidence that zic2 function limits Hh signaling. RNA-seq transcriptome analysis identified an early requirement for zic2 in periocular neural crest as an activator of alx1, a transcription factor with essential roles in craniofacial and ocular morphogenesis in human and zebrafish. Collectively, these data establish zic2 mutant zebrafish as a powerful new genetic model for in-depth dissection of cell interactions and genetic controls during craniofacial complex development.
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Affiliation(s)
- Irina Sedykh
- Department of Integrative Biology, University of Wisconsin, Madison, WI 53706, USA; Department of Neuroscience, University of Wisconsin, Madison, WI 53706, USA
| | - Baul Yoon
- Department of Integrative Biology, University of Wisconsin, Madison, WI 53706, USA; Department of Neuroscience, University of Wisconsin, Madison, WI 53706, USA; Genetics Ph. D. Training Program, University of Wisconsin, Madison, WI 53706, USA
| | - Laura Roberson
- Department of Integrative Biology, University of Wisconsin, Madison, WI 53706, USA; Department of Neuroscience, University of Wisconsin, Madison, WI 53706, USA
| | - Oleg Moskvin
- Primate Research Center, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Colin N Dewey
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Yevgenya Grinblat
- Department of Integrative Biology, University of Wisconsin, Madison, WI 53706, USA; Department of Neuroscience, University of Wisconsin, Madison, WI 53706, USA; McPherson Eye Research Institute, University of Wisconsin, Madison, WI, 53706, USA.
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Carucci N, Cacci E, Nisi PS, Licursi V, Paul YL, Biagioni S, Negri R, Rugg-Gunn PJ, Lupo G. Transcriptional response of Hoxb genes to retinoid signalling is regionally restricted along the neural tube rostrocaudal axis. ROYAL SOCIETY OPEN SCIENCE 2017; 4:160913. [PMID: 28484611 PMCID: PMC5414248 DOI: 10.1098/rsos.160913] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 03/07/2017] [Indexed: 06/07/2023]
Abstract
During vertebrate neural development, positional information is largely specified by extracellular morphogens. Their distribution, however, is very dynamic due to the multiple roles played by the same signals in the developing and adult neural tissue. This suggests that neural progenitors are able to modify their competence to respond to morphogen signalling and autonomously maintain positional identities after their initial specification. In this work, we take advantage of in vitro culture systems of mouse neural stem/progenitor cells (NSPCs) to show that NSPCs isolated from rostral or caudal regions of the mouse neural tube are differentially responsive to retinoic acid (RA), a pivotal morphogen for the specification of posterior neural fates. Hoxb genes are among the best known RA direct targets in the neural tissue, yet we found that RA could promote their transcription only in caudal but not in rostral NSPCs. Correlating with these effects, key RA-responsive regulatory regions in the Hoxb cluster displayed opposite enrichment of activating or repressing histone marks in rostral and caudal NSPCs. Finally, RA was able to strengthen Hoxb chromatin activation in caudal NSPCs, but was ineffective on the repressed Hoxb chromatin of rostral NSPCs. These results suggest that the response of NSPCs to morphogen signalling across the rostrocaudal axis of the neural tube may be gated by the epigenetic configuration of target patterning genes, allowing long-term maintenance of intrinsic positional values in spite of continuously changing extrinsic signals.
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Affiliation(s)
- Nicoletta Carucci
- Department of Biology and Biotechnology ‘C. Darwin’, Sapienza University of Rome, 00185 Rome, Italy
| | - Emanuele Cacci
- Department of Biology and Biotechnology ‘C. Darwin’, Sapienza University of Rome, 00185 Rome, Italy
| | - Paola S. Nisi
- Department of Biology and Biotechnology ‘C. Darwin’, Sapienza University of Rome, 00185 Rome, Italy
| | - Valerio Licursi
- Department of Biology and Biotechnology ‘C. Darwin’, Sapienza University of Rome, 00185 Rome, Italy
| | - Yu-Lee Paul
- Epigenetics Programme, The Babraham Institute, Cambridge CB22 3AT, UK
| | - Stefano Biagioni
- Department of Biology and Biotechnology ‘C. Darwin’, Sapienza University of Rome, 00185 Rome, Italy
| | - Rodolfo Negri
- Department of Biology and Biotechnology ‘C. Darwin’, Sapienza University of Rome, 00185 Rome, Italy
- Istituto Pasteur— Fondazione Cenci Bolognetti, Sapienza University of Rome, 00185 Rome, Italy
| | | | - Giuseppe Lupo
- Istituto Pasteur— Fondazione Cenci Bolognetti, Sapienza University of Rome, 00185 Rome, Italy
- Department of Chemistry, Sapienza University of Rome, 00185 Rome, Italy
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