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L.E. Kelly, H.M. El–Hodiri; The Forkhead Gene FoxN4 Is Expressed in Developing Retinal Progenitor Cells in Xenopus Laevis Embryos . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3138.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate the expression pattern and function of FoxN4, a putative regulator of the Rx2A (retinal homeobox 2A) gene promoter. Methods: Rx2A/GFP constructs were tested for activity in transgenic Xenopus laevis embryos generated by intracytosolic sperm injection (ICSI). We obtained a Xenopus laevis FoxN4 EST containing a portion of the coding region. The 5’–end of the FoxN4 coding region was generated by 5’–RACE using neurula cDNA. In situ hybridization was performed on Xenopus laevis embryos using digoxigenin–labeled antisense riboprobes. Results: The Rx2A promoter contains an essential cis–acting element predicted to interact with members of the forkhead family of transcription factors. We have isolated a Xenopus laevis cDNA encoding the forkhead transcription factor FoxN4. The expression pattern of FoxN4 is similar that of Rx during retinal development. FoxN4 expression is initiated in the presumptive eye field of neural plate stage embryos and continues in the developing neural retina. As is the case in other vertebrate species, Xenopus FoxN4 expression becomes restricted to regions where retinal progenitor cells develop. Expression diminishes as the retina matures. Overexpression of FoxN4 results in development of ectopic retinal tissue and anterior neural tube duplication, similar to the Xenopus Rx–overexpression phenotype. Additionally, overexpression of FoxN4 results in microphthalmia. These results are generally consistent with a role for FoxN4 in regulation of Rx transcription during Xenopus retinal development.
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