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XB-ART-39345
Dev Biol May 15, 2009; 329 (2): 258-68.

The Xenopus Irx genes are essential for neural patterning and define the border between prethalamus and thalamus through mutual antagonism with the anterior repressors Fezf and Arx.



Abstract
The Iroquois (Irx) genes encode homeoproteins conserved during evolution. Vertebrate genomes contain six Irx genes organized in two clusters, IrxA (which harbors Irx1, Irx2 and Irx4) and IrxB (which harbors Irx3, Irx5 and Irx6). To determine the precise role of these genes during development and their putative redundancies, we conducted a comparative expression analysis and a comprehensive loss-of-function study of all the early expressed Irx genes (Irx1-5) using specific morpholinos in Xenopus. We found that the five Irx genes display largely overlapping expression patterns and contribute to neural patterning. All Irx genes are required for proper formation of posterior forebrain, midbrain, hindbrain and, to a lesser an extent, spinal cord. Nevertheless, Irx1 and Irx3 seem to have a predominant role during regionalization of the neural plate. In addition, we find that the common anterior limit of Irx gene expression, which will correspond to the future border between the prethalamus and thalamus, is defined by mutual repression between Fezf and Irx proteins. This mutual repression is likely direct. Finally, we show that Arx, another anteriorly expressed repressor, also contribute to delineate the anterior border of Irx expression.

PubMed ID: 19268445
Article link: Dev Biol

Genes referenced: arx cdx4 dio3 egr2 en2 fezf1 fezf2 gbx2.1 gbx2.2 hnf1b irx1 irx2 irx3 irx4 irx5 irx6 mst1 neurog2 otx2 pax2 pax6 rax six2 six3 sox2 tubb2b wnt1 wnt4
Morpholinos: irx1 MO1 irx2 MO1 irx3 MO1 irx3 MO2 irx4 MO1 irx5 MO1


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