Expression dynamics of the LIM-homeobox genes, Lhx1 and Lhx9, in the diencephalon during chick development.

The diencephalon is the caudal part of the developing forebrain, which corresponds to prosomeres 1 to 3. The mature diencephalon is functionally and anatomically divided into well-defined nuclei. Previous researches have shown that LIM-homeobox genes are important transcription factors during diencephalon regionalization in mice. Here we examined expression patterns of several chick orthologs of LIM-homeobox genes. Lhx1 and Lhx9 were expressed in the diencephalon from early stages and their expression in the diencephalon became restricted to prosomeres 1 and 2 in distinct fashions. Then we also studied the regulatory effects of possible upstream signals by in ovo electroporation. Lhx1 was found to be up-regulated by Shh signaling. Whereas Lhx9 was up-regulated by Wnt3a and Fgf15, it was down-regulated by Shh. Our data suggest that the LIM-homeobox genes, Lhx1 and Lhx9, regulated by ventral and/or dorsal signals, may play important roles in controlling regionalization of the diencephalon during chick development.