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H.M. El-Hodiri; Identification and Characterization of a Xenopus Rx-like Gene . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2263.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The retinal homeobox gene, Rx, is essential for vertebrate eye development. Rx is expressed in the anterior neural plate and the developing eye fields of neural plate and neural tube stage embryos before any morphological evidence of eye development can be observed. To better understand Rx function, we sought to study Rx-related homeobox genes. Methods: The GenBank library est_others was searched using TBLASTN with the Rx1A coding sequence as query. We identified a Xenopus laevis EST encoding a Rx-related gene, Rx-L (Rx-like). The entire Rx-L EST was used a template to synthesize an antisense digoxygenin-labeled riboprobe for wholemount in situ hybridization. Synthetic Rx-L was prepared and injected into the prospective anterior neural plate region of 4-cell Xenopus laevis embryos. Electrophoretic mobility shift assays were performed using a PCE-1 probe and in vitro translated Rx-L protein. Results: Rx-L encodes a protein which exhibits 62% overall identity (75% similarity) to Xenopus Rx over the length of the coding region and higher similarity in the homeodomain. Rx-L is expressed in the developing eye of early tailbud embryos but is not expressed in neural plate or neural tube stage embryos. As eye development proceeds, Rx-L expression is restricted to the developing retina. Both Rx and Rx-L can bind the photoreceptor conserved element-1 (PCE-1). However, overexpression of Rx-L in Xenopus embryos does not induce development of ectopic retinal tissue. Conclusions: Rx-L encodes a protein that is similar to Rx but may function differently in regulating gene expression in eye development.
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