Abstract
Abstract: :
Purpose: The retinal homeobox (Rx) gene is among the earliest eye–specific genes expressed in the vertebrate embryo and is essential for eye development. Rx expression initiates in the anterior neural plate and continues throughout early eye development, becoming restricted to the developing photoreceptor layer of the neural retina. To better understand the genetic events leading to the initiation of Rx expression, we have sought to isolate and characterize the Rx promoter. The genome of the South African clawed frog, Xenopus laevis, encodes two Rx genes, Rx1A and Rx2A. The purpose of this work is to isolate and characterize the Rx2A promoter. We hope that comparison of the Rx1A and Rx2A promoters will lead to identification of conserved cis–acting transcriptional regulatory elements. Methods: DNA flanking the Rx2A cDNA was amplified from Xenopus laevis genomic DNA by linker–mediated PCR. And used to prepare a Rx2A/GFP transgene. The transgene was introduced into Xenopus laevis embryos using intracytosolic sperm injection (ICSI). Transgene expression (GFP) was visualized by fluorescent microscopy. Results: GFP expression was observed in the anterior neural plate, the developing eye fields, and photoreceptor layer of transgenic frog embryos and tadpoles. Conclusion: We have isolated a functional Rx2A promoter. We preliminarily conclude that it is active in essentially the same spatio–temporal pattern as the previously characterized Xenopus laevis Rx1A promoter and the endogenous Rx genes.
Keywords: gene/expression • transcription • retinal development