Purchase this article with an account.
E. M. Levine, E. Veien, S. Yun, R. L. Chow, R. Dorsky, A. M. Clark; Control of Retinal Development by the PrdL:CVC Genes Chx10 and Vsx1 is Evolutionarily Conserved. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5700.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Chx10 and Vsx1 (Rinx) are expressed in the retina and are likely to have arisen from a common ancestral gene. Each has distinct but important roles in ocular development. Mutations in Chx10 cause non-syndromic bilateral microphthalmia, a profound reduction in retinal progenitor cell (RPC) proliferation, and an absence of bipolar cells. Mutations in Vsx1 are associated with posterior polymorphous corneal dystrophy (PPCD) and abnormal cone bipolar cell function. Given their structural similarities and importance in ocular development, we sought to determine if a regulatory interaction exists between these genes and whether they are required in an absolute manner for retinal development.
Chx10 DNA-binding sites in the Vsx1 5’-intergenic region were identified using bioinformatics and Chx10 binding was examined by chromatin immunoprecipitation (ChIP) and gel shift assays (EMSA). Expression of Chx10 and Vsx1 was examined by immunohistochemistry, RT-PCR and western blot. Genetic requirements were examined in Chx10orj, Vsx1lacZ compound mutant mice and in zebrafish using morpholinos (MO).
Two Chx10 DNA-binding sites were found in the Vsx1 5’-intergenic region and Chx10 binds to one of these sites in vivo and in vitro. Consistent with the role of Chx10 as a transcriptional repressor, bipolar cells that express high levels of Chx10 protein express Vsx1 at low levels and vice versa, and Vsx1 mRNA is upregulated in the RPCs of Chx10orj mutant mice and zebrafish embryos injected with a Chx10 MO. In Chx10orj, Vsx1lacZ compound mutant mice and zebrafish embryos injected with Chx10 and Vsx1 MOs, the degree of microphthalmia and defects in retinal development is similar to embryos with Chx10 loss of function.
Vsx1 is a candidate direct target of Chx10-mediated transcriptional repression. Although Vsx1 mRNA is upregulated in RPCs lacking Chx10 in mice and zebrafish, Vsx1 does not functionally compensate for loss of Chx10. These observations suggest that PrdL:CVC genes are not absolutely required for vertebrate retinal development, but the regulatory relationship between Chx10 and Vsx1 could be important for generating bipolar cell diversity.
This PDF is available to Subscribers Only