CONTROL OF ANTEROPOSTERIOR AND DORSOVENTRAL DOMAINS OF NKX-6.1 GENE-EXPRESSION RELATIVE TO OTHER NKX GENES DURING VERTEBRATE CNS DEVELOPMENT

Here we report the isolation, sequence and developmental expression in the central nervous system of several members of the chicken and mous e Nkx gene family. These are among the earliest genes to be regionally expressed in the neural plate; they are expressed just above the axia l mesendoderm (prechordal mesendoderm and notochord). Each Nkx gene ha s a distinct spatial pattern of expression along the anterior-posterio r axis of the ventral central nervous system: Nkx-2.2 is expressed alo ng the entire axis, whereas Nkx-2.1 is restricted to the forebrain, an d Nkx-6.1 and Nkx-6.2 are largely excluded from the forebrain. They ar e also expressed in distinct patterns along the dorsal ventral axis. T hese genes are expressed in both the ventricular and mantle zones; in the mantle zone Nkx-6.1 is co-expressed with Islet-1 in a subset of mo tor neurons. Like other Nkx genes, expression of Nkx-6.1 is induced by the axial mesendoderm and by sonic hedgehog protein. BMP-7 represses Nkx-6.1 expression. While the notochord can induce Nkx-6.1 expression in the anterior neural plate, sonic hedgehog protein does not, suggest ing that the notochord produces additional molecules that can regulate ventral patterning. (C) 1998 Elsevier Science Ireland Ltd.