XB-ART-34399
Invest Ophthalmol Vis Sci
October 1, 2006;
47
(10):
4245-53.
The Rx-like homeobox gene (Rx-L) is necessary for normal photoreceptor development.
Abstract
The retinal homeobox (Rx) gene plays an essential role in retinal development. An Rx-like (
Rx-L) gene from Xenopus laevis has been identified. The purpose of this study was to analyze the function of
Rx-L in the developing
retina. DNA-binding properties of
Rx-L were analyzed by electrophoretic mobility shift assay (EMSA), with in vitro-translated proteins and radiolabeled oligonucleotide probe. The
Rx-L expression pattern was analyzed by in situ hybridization using whole or sectioned embryos and digoxigenin-labeled antisense riboprobes.
Rx-L loss of function was studied by using antisense morpholino oligonucleotides targeted to the
Rx-L translation initiation site. Embryos injected with control or
Rx-L morpholinos were analyzed at
stage 41 or 45.
Rx-L shares homology with Rx at the homeo-, OAR, and Rx domains, but lacks an octapeptide motif.
Rx-L is expressed in the developing
retina beginning in the
early tailbud stage. In the maturing
retina,
Rx-L expression is restricted primarily to the developing
photoreceptor layer and the
ciliary marginal zone.
Rx-L can bind a photoreceptor conserved element-1 (
PCE-1) oligonucleotide, an element conserved among all known photoreceptor gene promoters. In a promoter activity assay,
Rx-L functions as a stronger transcriptional activator than Rx. Antisense morpholino-mediated knockdown of
Rx-L expression resulted in a decrease in
rhodopsin and
red cone opsin expression levels in Xenopus retinas. Injection of the
Rx-L antisense morpholino oligonucleotide also resulted in a decrease in the length of both rod and cone outer segments. The results suggest that
Rx-L functions to regulate rod and cone development by activating photoreceptor-specific gene expression.
PubMed ID:
17003412
PMC ID:
PMC2824340
Article link:
Invest Ophthalmol Vis Sci
Grant support:
[+]
Species referenced:
Xenopus
Genes referenced:
ces3.7
opn1lw
rax2
rho
Antibodies:
Isl1/2 Ab1
Morpholinos:
rax2 MO1
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