Fig 7 - uploaded by Wen Wen
Content may be subject to copyright.
Overexpression of sox4 inhibits Hh ligand expression and causes cyclopia. (A-F) Representative images of embryos injected with control tdTomato or sox4 mRNA. (A-B) Representative images of the head were taken at 72 hpf from the ventral side. (C-F) Lateral views of body showing the somites. Insets in (C) and (D) were enlarged in (E) and (F). (G) Quantification of the percentage of cyclopia in embryos injected with different combinations of control and sox4 mRNA. 1.0 ng/embryo Td-tomato: 0.767 1.31%, n? 1/108; 0.2 ng sox4a/b ? 0.6 ng Td-tomato/embryo: 9.357 1.17%, n? 13/139; 0.3 ng sox4a/b ? 0.4 ng Td-tomato/embryo: 17.03 7 3.69%, n? 11/67; 0.4 ng sox4a/b ?0.2 ng Td-tomato/embryo: 25.56 7 2.20%, n? 25/97. (H) qPCR analysis of ihhb and shha expression in control and sox4 overexpressing heads at 18 and 24 hpf. In sox4 mRNA injected embryos, ihhb expression was significantly decreased by 1.61-fold at 18 hpf (Student's t-test, P o0.05) and 1.51-fold at 24 hpf (Student's t-test, P ?0.057). Shha expression was also significantly reduced following sox4 mRNA injection at both 18 and 24 hpf (by 1.82-fold and 3.57-fold, respectively; Student's t-test, P o 0.05).
Source publication
SoxC transcription factors play critical roles in many developmental processes, including
neurogenesis, cardiac formation, and skeletal differentiation. In vitro and in vivo loss-of-function
studies have suggested that SoxC genes are required for oculogenesis, however the mechanism was
poorly understood. Here, we have explored the function of the S...
Contexts in source publication
Context 1
... knockdown of Sox4 caused an elevation in ihhb expression and Hh signaling, we predicted that overexpression of Sox4 would result in a corresponding reduction in Hh activity. We injected in- vitro synthesized control or sox4a/b mRNA into wild type embryos, and scored the injected embryos at 24 hpf for the presence of cyclopia, a phenotype associated with reduced Hh activity from the midline ( Ekker et al., 1995). Whereas only 0.7871.34% of embryos (n?1/128) injected with a control Td-Tomato mRNA exhibited cyclo- pia, we detected cyclopia in 36.5475.10% (n?38/104) of the sox4 mRNA-injected embryos ( Fig. 7A and B). In addition, we found that the cyclopic embryos often possessed a truncated body and U-shaped somites (Fig. 7C-F), a phenotype that is also observed with reductions in Hh signaling ( Currie and Ingham, 1996;Schauerte et al., 1998;Wolff et al., 2003). To confirm that the cyclopic phenotype was specific for overexpression of sox4, we injected the same total amount of mRNA containing different ratios of control Td-Tomato and sox4 mRNA. We observed that both the occurrence and severity of cyclopia increased with increasing concentration of sox4 mRNA (Fig. 7G), strongly suggesting that the cyclopic phenotype was not an artifact of mRNA injection. qPCR performed on mRNA prepared from the heads of injected embryos confirmed that ihhb expression was reduced in the embryos overexpressing sox4 at 18 and 24 hpf, although the reduction was not statistically significant at 24 hpf ( Fig. 7H; Student's t-test, P?0.0565). Surprisingly, although sox4 knockdown did not affect the expression level of shha, sox4 overexpression significantly reduced the expression of shha in the head. Taken together, these data suggest that sox4 can negatively regulate the expression of both ihhb and shha, and that overexpression of sox4 causes a reduction in midline Hh activity, leading to ...
Context 2
... knockdown of Sox4 caused an elevation in ihhb expression and Hh signaling, we predicted that overexpression of Sox4 would result in a corresponding reduction in Hh activity. We injected in- vitro synthesized control or sox4a/b mRNA into wild type embryos, and scored the injected embryos at 24 hpf for the presence of cyclopia, a phenotype associated with reduced Hh activity from the midline ( Ekker et al., 1995). Whereas only 0.7871.34% of embryos (n?1/128) injected with a control Td-Tomato mRNA exhibited cyclo- pia, we detected cyclopia in 36.5475.10% (n?38/104) of the sox4 mRNA-injected embryos ( Fig. 7A and B). In addition, we found that the cyclopic embryos often possessed a truncated body and U-shaped somites (Fig. 7C-F), a phenotype that is also observed with reductions in Hh signaling ( Currie and Ingham, 1996;Schauerte et al., 1998;Wolff et al., 2003). To confirm that the cyclopic phenotype was specific for overexpression of sox4, we injected the same total amount of mRNA containing different ratios of control Td-Tomato and sox4 mRNA. We observed that both the occurrence and severity of cyclopia increased with increasing concentration of sox4 mRNA (Fig. 7G), strongly suggesting that the cyclopic phenotype was not an artifact of mRNA injection. qPCR performed on mRNA prepared from the heads of injected embryos confirmed that ihhb expression was reduced in the embryos overexpressing sox4 at 18 and 24 hpf, although the reduction was not statistically significant at 24 hpf ( Fig. 7H; Student's t-test, P?0.0565). Surprisingly, although sox4 knockdown did not affect the expression level of shha, sox4 overexpression significantly reduced the expression of shha in the head. Taken together, these data suggest that sox4 can negatively regulate the expression of both ihhb and shha, and that overexpression of sox4 causes a reduction in midline Hh activity, leading to ...
Context 3
... knockdown of Sox4 caused an elevation in ihhb expression and Hh signaling, we predicted that overexpression of Sox4 would result in a corresponding reduction in Hh activity. We injected in- vitro synthesized control or sox4a/b mRNA into wild type embryos, and scored the injected embryos at 24 hpf for the presence of cyclopia, a phenotype associated with reduced Hh activity from the midline ( Ekker et al., 1995). Whereas only 0.7871.34% of embryos (n?1/128) injected with a control Td-Tomato mRNA exhibited cyclo- pia, we detected cyclopia in 36.5475.10% (n?38/104) of the sox4 mRNA-injected embryos ( Fig. 7A and B). In addition, we found that the cyclopic embryos often possessed a truncated body and U-shaped somites (Fig. 7C-F), a phenotype that is also observed with reductions in Hh signaling ( Currie and Ingham, 1996;Schauerte et al., 1998;Wolff et al., 2003). To confirm that the cyclopic phenotype was specific for overexpression of sox4, we injected the same total amount of mRNA containing different ratios of control Td-Tomato and sox4 mRNA. We observed that both the occurrence and severity of cyclopia increased with increasing concentration of sox4 mRNA (Fig. 7G), strongly suggesting that the cyclopic phenotype was not an artifact of mRNA injection. qPCR performed on mRNA prepared from the heads of injected embryos confirmed that ihhb expression was reduced in the embryos overexpressing sox4 at 18 and 24 hpf, although the reduction was not statistically significant at 24 hpf ( Fig. 7H; Student's t-test, P?0.0565). Surprisingly, although sox4 knockdown did not affect the expression level of shha, sox4 overexpression significantly reduced the expression of shha in the head. Taken together, these data suggest that sox4 can negatively regulate the expression of both ihhb and shha, and that overexpression of sox4 causes a reduction in midline Hh activity, leading to ...
Context 4
... knockdown of Sox4 caused an elevation in ihhb expression and Hh signaling, we predicted that overexpression of Sox4 would result in a corresponding reduction in Hh activity. We injected in- vitro synthesized control or sox4a/b mRNA into wild type embryos, and scored the injected embryos at 24 hpf for the presence of cyclopia, a phenotype associated with reduced Hh activity from the midline ( Ekker et al., 1995). Whereas only 0.7871.34% of embryos (n?1/128) injected with a control Td-Tomato mRNA exhibited cyclo- pia, we detected cyclopia in 36.5475.10% (n?38/104) of the sox4 mRNA-injected embryos ( Fig. 7A and B). In addition, we found that the cyclopic embryos often possessed a truncated body and U-shaped somites (Fig. 7C-F), a phenotype that is also observed with reductions in Hh signaling ( Currie and Ingham, 1996;Schauerte et al., 1998;Wolff et al., 2003). To confirm that the cyclopic phenotype was specific for overexpression of sox4, we injected the same total amount of mRNA containing different ratios of control Td-Tomato and sox4 mRNA. We observed that both the occurrence and severity of cyclopia increased with increasing concentration of sox4 mRNA (Fig. 7G), strongly suggesting that the cyclopic phenotype was not an artifact of mRNA injection. qPCR performed on mRNA prepared from the heads of injected embryos confirmed that ihhb expression was reduced in the embryos overexpressing sox4 at 18 and 24 hpf, although the reduction was not statistically significant at 24 hpf ( Fig. 7H; Student's t-test, P?0.0565). Surprisingly, although sox4 knockdown did not affect the expression level of shha, sox4 overexpression significantly reduced the expression of shha in the head. Taken together, these data suggest that sox4 can negatively regulate the expression of both ihhb and shha, and that overexpression of sox4 causes a reduction in midline Hh activity, leading to ...
Similar publications
Establishment of precise three-dimensional tissue structure is vital for organ function. In the visual system, optic fissure and stalk morphogenesis is a crucial yet poorly understood process, disruptions of which can lead to coloboma, a birth defect causing visual impairment. Here, we use four-dimensional imaging, cell tracking, and molecular gene...
Citations
... Finally, recent studies have shown that control of Ihh signaling is fundamental in choroid fissure closure also in zebrafish morphants 41 , where ocular coloboma was found to be due to increased expression of the Hh pathway ligand Indian Hedgehog b (ihhb). Another study using zebrafish morphants found that the absence of Indian Hedgehog a (ihha) in zebrafish morphants led to smaller eyes 42 . ...
Genomic sequences residing within introns of few genes have been shown to act as enhancers affecting expression of neighboring genes. We studied an autosomal recessive phenotypic continuum of microphthalmia, anophthalmia and ocular coloboma, with no apparent coding-region disease-causing mutation. Homozygosity mapping of several affected Jewish Iranian families, combined with whole genome sequence analysis, identified a 0.5 Mb disease-associated chromosome 2q35 locus (maximal LOD score 6.8) harboring an intronic founder variant in NHEJ1 , not predicted to affect NHEJ1. The human NHEJ1 intronic variant lies within a known specifically limb-development enhancer of a neighboring gene, Indian hedgehog (Ihh), known to be involved in eye development in mice and chickens. Through mouse and chicken molecular development studies, we demonstrated that this variant is within an Ihh enhancer that drives gene expression in the developing eye and that the identified variant affects this eye-specific enhancer activity. We thus delineate an Ihh enhancer active in mammalian eye development whose variant causes human microphthalmia, anophthalmia and ocular coloboma. The findings highlight disease causation by an intronic variant affecting the expression of a neighboring gene, delineating molecular pathways of eye development.
... ihhb plays an important role in vertebral column development in fugu (Takifugu rubripes) and is also associated with chondrogenic lineage in Atlantic salmon (Salmo salar L.) [59,60]. Abnormal ocular morphogenesis was observed in sox4-deficient zebrafish, resulting from elevated hedgehog signaling due to increased expression of the hedgehog pathway ligand (ihhb) [61]. ihhb was found to play a role in testis maturation [18], and target toll-like receptor 1 was found to perceive LPS stimulation and transfer signals to activate the NF-κB pathway or the TLR signaling pathway in miiuy croaker [62]. ...
17α-Methyltestosterone (17MT), a synthetic organic compound commonly found in sewage waters, can affect reproduction in aquatic animals, such as tilapia and yellow catfish. In the present study, male Gobiocypris rarus were exposed to 25, 50, and 100 ng/L of 17α-methyltestosterone (17MT) for 7 days. We first analyzed miRNA- and RNA-seq results to determine miRNA-target gene pairs and then developed miRNA-mRNA interactive networks after 17MT administration. Total weights, total lengths, and body lengths were not significantly different between the test groups and control groups. The paraffin slice method was applied to testes of G. rarus in the MT exposure and control groups. We found that there were more mature sperm (S) and fewer secondary spermatocytes (SSs) and spermatogonia (SGs) in the testes of control groups. As 17MT concentration increased, fewer and fewer mature sperm (S) were observed in the testes of male G. rarus. The results showed that FSH, 11-KT, and E2 were significantly higher in individuals exposed to 25 ng/L 17MT compared with the control groups. VTG, FSH, LH, 11-KT, and E2 were significantly lower in the 50 ng/L 17MT exposure groups compared to the control groups. VTG, FSH, LH, 11-KT, E2, and T were significantly lower in the groups exposed to 100 ng/L 17MT. High-throughput sequencing revealed 73,449 unigenes, 1205 known mature miRNAs, and 939 novel miRNAs in the gonads of G. rarus. With miRNA-seq, 49 (MT25-M vs. Con-M), 66 (MT50-M vs. Con-M), and 49 (MT100-M vs. Con-M) DEMs were identified in the treatment groups. Five mature miRNAs (miR-122-x, miR-574-x, miR-430-y, lin-4-x, and miR-7-y), as well as seven differentially expressed genes (soat2, inhbb, ihhb, gatm, faxdc2, ebp, and cyp1a1), which may be associated with testicular development, metabolism, apoptosis, and disease response, were assayed using qRT-PCR. Furthermore, miR-122-x (related to lipid metabolism), miR-430-y (embryonic development), lin-4-x (apoptosis), and miR-7-y (disease) were differentially expressed in the testes of 17MT-exposed G. rarus. This study highlights the role of miRNA-mRNA pairs in the regulation of testicular development and immune response to disease and will facilitate future studies on the miRNA-RNA-associated regulation of teleost reproduction.
... In this manuscript, we demonstrate that rerea mutant zebrafish exhibit several developmental eye defects, including an enlarged optic stalk (OS), coloboma, disruption of the OS/neuro-retina boundary, and the presence of ectopic retinal tissue in the ventral diencephalon region. The coloboma and blowout-like phenotype observed in rerea mutant embryos is morphologically similar to that observed in patched1, 12 aussicht, 13 six3a: six3b mutants, 14 and zebrafish morphants for sox11, 15 sox4, 16 and vax1:vax2. 17 These observations suggest that deregulation of protein signaling could be involved in ophthalmic defects associated with rerea mutants. ...
... Cyclopamine, a smoothened inhibitor, has been previously used to rescue the coloboma phenotype associated with upregulated shh signaling. 12,15,16 We used cyclopamine (5 μM treatment from 5.5 to 13.5 hpf) to rescue the coloboma phenotype in rerea mutant embryos but did not observe any rescue (data not shown). Higher doses of cyclopamine (100 μM) did cause cyclopia in embryos obtained from the same breeding (data not shown). ...
... Higher doses of cyclopamine (100 μM) did cause cyclopia in embryos obtained from the same breeding (data not shown). This observation was in contrast to what has been observed previously with other alterations of the pathway, 12,15,16 where the coloboma phenotype due to upregulated shh signaling was significantly rescued by cyclopamine treatment from 5.5 to 13.5 hpf. 12 Also, treatment of rerea heterozygous and homozygous mutant embryos with smoothened agonist purmorphamine (75 μM, 5.5-24 hpf) did not increase the percentage of embryos displaying coloboma or the severity of phenotype (data not shown), as has been reported previously. ...
Background
RERE is a highly conserved transcriptional co‐regulator that is associated with a human neurodevelopmental disorder with or without anomalies of the brain, eye, or heart (NEDBEH, OMIM: 616975).
Results
We show that the zebrafish rerea mutant (babyface) robustly recapitulates optic fissure closure defects resulting from loss of RERE function, as observed in humans. These defects result from expansion of proximal retinal optic stalk (OS) and reduced expression of some of the ventral retinal fate genes due to deregulated protein signaling. Using zebrafish and cell‐based assays, we determined that NEDBEH‐associated human RERE variants function as hypomorphs in their ability to repress shh signaling and some exhibit abnormal nuclear localization. Inhibiting shh signaling by the protein inhibitor HPI‐1 rescues coloboma, confirming our observation that coloboma in rerea mutants is indeed due to deregulation of shh signaling.
Conclusions
Zebrafish rerea mutants exhibit OS and optic fissure closure defects. The optic fissure closure defect was rescued by an shh signaling inhibitor, suggesting that this defect could arise due to deregulated shh signaling.
... At 72 hpf, embryos were fixed in 4% paraformaldehyde overnight, then incubated in 10% followed by 30% sucrose at 4 °C. Sectioning and immunohistochemistry were conducted as previously described 46 and immunolabeled sections were imaged on either a Nikon inverted (Nikon Ti-U) or confocal microscope (Leica SP8, Leica). The following antibodies were used: anti-4C12 (immature and mature rod photoreceptors, mouse, 1:100, provided by James Fadool, Florida State University) and anti-Zpr1 (red/green cone photoreceptors, 1:20, mouse, ZIRC). ...
NR2E3 is an orphan nuclear receptor whose loss-of-function causes abnormal retinal photoreceptor development and degeneration. However, despite that many nuclear receptors are regulated by binding of small molecule ligands, biological small molecule ligands regulating NR2E3 have not been identified. Identification of an endogenous NR2E3 ligand might reveal a previously unrecognized component contributing to retinal development and maintenance. Here we report that biliverdin, a conserved green pigment from heme catabolism, regulates NR2E3 and is necessary for zebrafish retinal photoreceptor development. Biliverdin from retinal extracts specifically bound to NR2E3’s ligand-binding domain and induced NR2E3-dependent reporter gene expression. Inhibition of biliverdin synthesis decreased photoreceptor cell populations in zebrafish larvae, and this phenotype was alleviated by exogenously supplied biliverdin. Thus, biliverdin is an endogenous small molecule ligand for NR2E3 and a component necessary for the proper development of photoreceptor cells. This result suggests a possible role of heme metabolism in the regulation of retinal photoreceptor cell development.
... Sectioning and immunohistochemistry were conducted as previously described (Wen et al., 2015) and immunolabeled sections were imaged on either a Nikon inverted (Nikon Ti-U) or confocal microscope (Leica SP8, Leica). The following antibodies were used: anti-Zpr3 ...
Diabetes is linked to various long-term complications in adults, such as neuropathy, nephropathy, and diabetic retinopathy. Diabetes poses additional risks for pregnant women, because glucose passes across the placenta, and excess maternal glucose can result in diabetic embryopathy. While many studies have examined the teratogenic effects of maternal diabetes on fetal heart development, little is known about the consequences of maternal hyperglycemia on the development of the embryonic retina. To address this question, we investigated retinal development in two models of embryonic hyperglycemia in zebrafish. Strikingly, we found that hyperglycemic larvae displayed a significant reduction in photoreceptors and horizontal cells, whereas other retinal neurons were not affected. We also observed reactive gliosis and abnormal optokinetic responses in hyperglycemic larvae. Further analysis revealed delayed retinal cell differentiation in hyperglycemic embryos that coincided with increased reactive oxygen species (ROS). Our results suggest that embryonic hyperglycemia causes abnormal retinal development via altered timing of cell differentiation and ROS production, which is accompanied by visual defects. Further studies using zebrafish models of hyperglycemia will allow us to understand the molecular mechanisms underlying these effects.
... How do the cells and organisms sense and transfer the cold signals? Calcium signaling was reported to mediate cold sensing in insect tissues [54], but the involvement in cold sensing and signaling of fish remains unknown. What are the upstream regulators responsible for activating the Foxo transcription factors and the ERK and p38 MAPKs? ...
Low temperature stress represents a major threat to the lives of both farmed and wild fish species. However, biological pathways determining the development of cold resistance in fish remain largely unknown. Zebrafish larvae at 96 hpf were exposed to lethal cold stress (10 °C) for different time periods to evaluate the adverse effects at organism, tissue and cell levels. Time series RNA sequencing (RNA-seq) experiments were performed to delineate the transcriptomic landscape of zebrafish larvae under cold stress and during the subsequent rewarming phase. The genes regulated by cold stress were characterized by progressively enhanced or decreased expression, whereas the genes associated with rewarming were characterized by rapid upregulation upon return to normal temperature (28 °C). Genes such as trib3, dusp5 and otud1 were identified as the representative molecular markers of cold-induced damages through network analysis. Biological pathways involved in cold stress responses were mined from the transcriptomic data and their functions in regulating cold resistance were validated using specific inhibitors. The autophagy, FoxO and MAPK (mitogen-activated protein kinase) signaling pathways were revealed to be survival pathways for enhancing cold resistance, while apoptosis and necroptosis were the death pathways responsible for cold-induced mortality. Functional mechanisms of the survival-enhancing factors Foxo1, ERK (extracellular signal-regulated kinase) and p38 MAPK were further characterized by inhibiting their activities upon cold stress and analyzing gene expression though RNA-seq. These factors were demonstrated to determine the cold resistance of zebrafish through regulating apoptosis and p53 signaling pathway. These findings have provided novel insights into the stress responses elicited by lethal cold and shed new light on the molecular mechanisms underlying cold resistance of fish.
... Mutant animal models of these retinal genes are characterized by anophthalmia, microphthalmia, and coloboma. Similarly, knockdown of the NC-specific transcription factor, SRY-box transcription factor 4a (Sox4a), also causes coloboma, as decreased Sox4 gene expression results in the mislocalization of Pax2a, Vsx1, and Vsx2 within the retina (Wen et al., 2015). Thus, early eye morphogenesis and cranial NC development intersect at multiple points, with important crosstalk between the tissues that regulate optic cup formation and direct NC migration. ...
During vertebrate embryonic development, a population of dorsal neural tube-derived stem cells, termed the neural crest (NC), undergo a series of morphogenetic changes and extensive migration to become a diverse array of cell types. Around the developing eye, this multipotent ocular NC cell population, called the periocular mesenchyme (POM), comprises migratory mesenchymal cells that eventually give rise to many of the elements in the anterior of the eye, such as the cornea, sclera, trabecular meshwork, and iris. Molecular cell biology and genetic analyses of congenital eye diseases have provided important information on the regulation of NC contributions to this area of the eye. Nevertheless, a complete understanding of the NC as a contributor to ocular development remains elusive. In addition, positional information during ocular NC migration and the molecular pathways that regulate end tissue differentiation have yet to be fully elucidated. Further, the clinical challenges of ocular diseases, such as Axenfeld-Rieger syndrome (ARS), Peters anomaly (PA) and primary congenital glaucoma (PCG), strongly suggest the need for better treatments. While several aspects of NC evolution have recently been reviewed, this discussion will consolidate the most recent current knowledge on the specification, migration, and contributions of the NC to ocular development, highlighting the anterior segment and the knowledge obtained from the clinical manifestations of its associated diseases. Ultimately, this knowledge can inform translational discoveries with potential for sorely needed regenerative therapies.
... Similarly in zebrafish, sox4 and sox11 act by limiting hh expression within the ventral forebrain adjacent to the optic vesicle. Furthermore, knockdown of Sox4 or Sox11 results in colobomas in zebrafish [81,82]. While both of these SoxC transcription factors are expressed in the forebrain, sox4 is also expressed in neural crest cells in the periocular mesenchyme and together with zic2b may have a cell non-autonomous effects on optic cup development [82]. ...
... Furthermore, knockdown of Sox4 or Sox11 results in colobomas in zebrafish [81,82]. While both of these SoxC transcription factors are expressed in the forebrain, sox4 is also expressed in neural crest cells in the periocular mesenchyme and together with zic2b may have a cell non-autonomous effects on optic cup development [82]. Down-regulation of zic2b, sox4, or sox11 causes mis-localization of pax2a, vsx1, and vsx2, which are necessary for dorsal and ventral patterning of the retina and subsequent ocular fissure closure [79,81,82]. ...
... While both of these SoxC transcription factors are expressed in the forebrain, sox4 is also expressed in neural crest cells in the periocular mesenchyme and together with zic2b may have a cell non-autonomous effects on optic cup development [82]. Down-regulation of zic2b, sox4, or sox11 causes mis-localization of pax2a, vsx1, and vsx2, which are necessary for dorsal and ventral patterning of the retina and subsequent ocular fissure closure [79,81,82]. Although later in development during retinal ganglion cell differentiation, zic2 antagonizes the expression of sox4 and sox11 in patterning axonal projections, the interplay between zic2 and sox4 in the neural crest has not been determined [83]. ...
The neural crest is a unique, transient stem cell population that is critical for craniofacial and ocular development. Understanding the genetics underlying the steps of neural crest development is essential for gaining insight into the pathogenesis of congenital eye diseases. The neural crest cells play an under-appreciated key role in patterning the neural epithelial-derived optic cup. These interactions between neural crest cells within the periocular mesenchyme and the optic cup, while not well-studied, are critical for optic cup morphogenesis and ocular fissure closure. As a result, microphthalmia and coloboma are common phenotypes in human disease and animal models in which neural crest cell specification and early migration are disrupted. In addition, neural crest cells directly contribute to numerous ocular structures including the cornea, iris, sclera, ciliary body, trabecular meshwork, and aqueous outflow tracts. Defects in later neural crest cell migration and differentiation cause a constellation of well-recognized ocular anterior segment anomalies such as Axenfeld–Rieger Syndrome and Peters Anomaly. This review will focus on the genetics of the neural crest cells within the context of how these complex processes specifically affect overall ocular development and can lead to congenital eye diseases
... In humans, a subpopulation of colobomata is a result of mutations in developmentally important genes; however, the origins for many OF closure defects are unknown (for reviews, see 3,7,8,13,14). Additional genes have been identified in animal models; substantial progress has been made in understanding critical processes, including growth and patterning of the ventral optic cup and optic nerve head (15)(16)(17)(18)(19), cell-cell contact and signaling (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), crosstalk with migrating hyaloid precursors and extracellular matrix components (31)(32)(33)(34)(35)(36), cytoskeleton dynamics (37,38), epigenetics (39), degradation of ECM and cellular proteins (40)(41)(42), programmed cell death, survival and cell proliferation (43,44) (for reviews, see 7,8,13). Elegant in vivo imaging studies in zebrafish and excellent anatomical analyses in chick have characterized important morphogenetic and cellular behavior (20,27,34,(45)(46)(47)(48)(49). ...
Uveal coloboma represents one of the most common congenital ocular malformations accounting for up to 10% of childhood blindness (1~ in 5,000 live birth). Coloboma originates from defective fusion of the optic fissure (OF), a transient gap that forms during eye morphogenesis by asymmetric, ventral invagination. Genetic heterogeneity combined with the activity of developmentally regulated genes suggest multiple mechanisms regulating OF closure. The tumor suppressor and FERM domain protein neurofibromin 2 (NF2) controls diverse processes in cancer, development and regeneration, via Hippo pathway and cytoskeleton regulation. In humans, NF2 mutations can cause ocular abnormalities, including coloboma, however, its actual role in OF closure is unknown. Using conditional inactivation in the embryonic mouse eye, our data indicates that loss of Nf2 function results in a novel underlying cause for coloboma. In particular, mutant eyes show substantially increased RPE proliferation in the fissure region with concomitant acquisition of RPE cell fate. Cells lining the OF margin can maintain RPE fate ectopically and fail to transition from neuroepithelial to cuboidal shape. In the dorsal RPE of the optic cup, Nf2 inactivation leads to a robust increase in cell number, with local disorganization of the cytoskeleton components F-actin and pMLC2. We propose that RPE hyperproliferation is the primary cause for the observed defects causing insufficient alignment of the OF margins in Nf2 mutants and failure to fuse properly, resulting in persistent coloboma. Our findings indicate that limiting proliferation particularly in the RPE layer is a critical mechanism during optic fissure closure
... The SOX11 transcript is heavily expressed in developing retina during embryonic stages 53 . It is required for the maintenance of hedgehog signaling and is critical for axonal growth, extension and driving adult neurogenesis [54][55][56] . The expression of SOX11 significantly increased in LSBX and LX conditions when compared to LSB and CHIR in RPCs at DIV23. ...
