Expression and regulation of the chicken Nkx-6.2 homeobox gene suggest itspossible involvement in the ventral neural patterning and cell fate specification

Rapid accumulating evidence has suggested that the homeodomain transcriptio n factors of the Nkx family play important roles in controlling vertebrate organ patterning and differentiation. In this study, we report the cloning, expression and regulation of a novel chicken homeobox gene, cNkx-6.2, whos e expression is similar, but not identical, to that of mouse Nkx-6.2. The e arliest expression of cNkx-6.2 was detected at the neural plate stage in th e prospective midbrain and hindbrain regions, As the neural development pro ceeds, cNkx-6.2 expression was restricted in the ventral region of the enti re neural axis except the forebrain region, At late stages of development, cNkx-6.2 expression is downregulated in the ventricular neuroepithelial cel ls, but subsequently upregulated in a subpopulation of cells, Tissue recomb ination and explant culture experiments demonstrated that expression of cNk x-6.2 can be induced by the notochord signal and purified SHH protein, and repressed by BMP-4 and -7, indicating that the cNkx-6.2 expression can be i nfluenced by both ventral and dorsal midline signals, Taken together, these studies have suggested two different roles for the cNkx-6.2 transcription factor: participating in the Shh-initiated ventral patterning during early CNS development and controlling cell fate specification and differentiation during late development. (C) 1999 Wiley-Liss, Inc.