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Lakshmi Pillai-Kastoori, Wen Wen, Stephen Wilson, Erin Strachan, Ordan Lehmann, Ann Morris; Sox11 is required to maintain proper levels of Hedgehog signaling during vertebrate ocular development. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3753.
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© ARVO (1962-2015); The Authors (2016-present)
The SRY-Box transcription factor Sox11 is expressed in the embryonic and adult nervous system and functions as a regulator of cell fate, survival, and differentiation. Previously, we have shown that Sox11 is synergistically required for the closure of the choroid fissure as well as rod photoreceptor differentiation. In this study, we describe the mechanism of action of Sox11 during ocular development in zebrafish and characterize the activity of human SOX11 sequence variants.
Translation blocking morpholinos were injected into 1-cell stage zebrafish embryos. The embryos were collected at different time points and processed for whole-mount in situ hybridization and immunohistochemical examination. Control and sox11 morphant embryos were treated with cyclopamine (2µM) between 5.5-13 hours post fertilization. DNA samples from 79 probands with MAC (microphthalmia, anophthalmia, and/or colobomata) were screened by sequencing the complete SOX11 coding sequence. Control samples were screened by sequencing and/or restriction enzyme digestion of PCR products. In vitro transcribed zebrafish and human SOX11 mRNA was co-injected with sox11morpholinos into zebrafish embryos at the 1-cell stage.
Knockdown of sox11 resulted in coloboma, which was accompanied by expanded expression of the proximal optic vesicle marker pax2.1. The morphant ocular phenotypes, including the rod photoreceptor deficit could be rescued by pharmacological inhibition of the Hedgehog pathway. Two heterozygous mutations were identified in the MAC patient panel, a 488G→T nucleotide change, and a 12 nucleotide in-frame insertion. The 488G→T mutation was absent from 368 control DNA samples and the dbSNP database. The second mutation, however, was present (n=3/370) in the control DNA population. In contrast to wild type human SOX11 mRNA, mRNA containing either mutation could not rescue the coloboma and rod photoreceptor deficiency in the zebrafish sox11morphants.
Our results reveal that Sox11 regulates early ocular and photoreceptor development in part by maintaining proper levels of Hedgehog signaling. Additionally, the combined human and model organism data provide compelling evidence for the requirement for of Sox11 in human ocular development.
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