Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
The aristaless-related gene, Arx, plays a fundamental role in
patterning the brain in humans and mice. Arx mutants exhibit
lissencephaly among other anomalies. We have cloned a Xenopus aristaless
homolog that appears to define specific regions of the developing
forebrain. xArx2 is transcribed in blastula through neurula stages, and
comes to be restricted to the ventral and lateral telencephalon, lateral
diencephalon, neural floor plate of the anterior spinal cord, and
somites. In this respect, Arx2 expresses in regions similar to Arx with
the exception of the somites. Overexpression enlarges the telencephalon,
and interference by means of antisense morpholino-mediated translation
knockdown reduces growth of this area. Overexpression and inhibition
studies demonstrate that misregulation of xArx2 imposes dire
consequences upon patterns of differentiation not only in the forebrain
where the gene normally expresses, but also in more caudal brain
territories and derivatives as well. This suggests that evolutionary
changes that expanded Arx-expression from ventral to dorsal
prosencephalon might be one of the determinants that marked development
and expansion of the telencephalon. genesis
Volume 47, Issue 1, pages 19–31, January 2009