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Dev Biol 2009 Mar 15;3272:352-65. doi: 10.1016/j.ydbio.2008.12.017.
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The role of Xenopus Rx-L in photoreceptor cell determination.

Wu HY , Perron M , Hollemann T .

Members of the Rx (retinal homeobox) gene family play vital roles during eye development. In Xenopus, as in most other vertebrates, two Rx-type genes have been described. While Rx1 deficiency led to loss of optic vesicles and impaired the proper development of ventral forebrain structures, a recently isolated second Rx-gene, Rx-L, seems to function in late retinogenesis. Here, we report that the specific suppression of Xenopus Rx-L function impaired the formation of the photoreceptor layer and reduced the expression of photoreceptor specific genes. Overexpression of Xenopus Rx-L induced ectopic expression of photoreceptor specific genes, but did only marginally promote the proliferation of retinal progenitor cells. Targeted overexpression of Rx-L in developing retinoblasts in vivo led to an increased fraction of photoreceptor cells at the expense of amacrine and bipolar cells and revealed that Rx-L acts as a transcription activator. A phylogenic analysis of all reported Rx-type genes revealed that they could be grouped into three categories, including an "invertebrate Rx" group, a "classical vertebrate Rx" group, and a "vertebrate Qrx/Rx-L" group. Taken together, Rx-L, unlike Rx1, is required for the determination of retinal cell types, especially photoreceptors, rather than for proliferation of retinal progenitors.

PubMed ID: 19135436
Article link: Dev Biol

Species referenced: Xenopus laevis
Genes referenced: adm arrb2 calb1 gal.2 pax6 pou4f1 prox1 rax rax2 rho rpe six3 vsx1
Antibodies: Calb1 Ab2
Morpholinos: rax2 MO2

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