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Dev Dyn 2005 Feb 01;2322:313-24. doi: 10.1002/dvdy.20234.
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Xenopus aristaless-related homeobox (xARX) gene product functions as both a transcriptional activator and repressor in forebrain development.

Seufert DW , Prescott NL , El-Hodiri HM .

Mutations in the aristaless-related homeobox (ARX) gene have been found in patients with a variety of X-linked mental retardation syndromes with forebrain abnormalities, including lissencephaly. Arx is expressed in the developing mouse, Xenopus, and zebrafish forebrain. We have used whole-mount in situ hybridization, overexpression, and loss-of-function studies to investigate the involvement of xArx in Xenopus brain development. We verified that xArx is expressed in the prospective diencephalon, as the forebrain is patterned and specified during neural plate stages. Expression spreads into the ventral and medial telencephalon as development proceeds through neural tube and tadpole stages. Overexpression of xArx resulted in morphological abnormalities in forebrain development, including loss of rostral midline structures, syn- or anophthalmia, dorsal displacement of the nasal organ, and ventral neural tube hyperplasia. Additionally, there is a delay in expression of many molecular markers of brain and retinal development. However, expression of some markers, dlx5 and wnt8b, was enhanced in xArx-injected embryos. Loss-of-function experiments indicated that xArx was necessary for normal forebrain development. Expansion of wnt8b expression depended on xArx function as a transcriptional repressor, whereas ectopic expression of dlx5, accompanied by development of ectopic otic structures, depended on function of Arx as a transcriptional activator. These results suggest that Arx acts as a bifunctional transcriptional regulator in brain development.

PubMed ID: 15614781
Article link: Dev Dyn

Species referenced: Xenopus laevis
Genes referenced: arx cdknx dlx5 emx1 en2 eomes foxg1 gal.2 lhx1 lhx2 lhx9 myc nkx2-1 otx1 otx2 pax2 pax6 rax shh vax2 wnt8b
Antibodies: Isl1/2 Ab1 Neuronal Ab5

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