Chick Homeobox Gene <i>cDlx</i> Expression Demarcates the Forebrain Anlage, Indicating the Onset of Forebrain Regional Specification at Gastrulation

Abstract

Here we describe the isolation and characterization of a chick homeobox-containing gene, cDlx, which shows greater than 85% homology to the homeodomain of other vertebrate Distal-less genes. Northern blot analysis and in situ hybridization studies reveal that cDlx expression is developmentally regulated and is tissue specific. In particular, the developmental expression pattern is characterized by an early appearance of cDlx transcript in the prospective forebrain region of gastrulating embryos. During neurulation, cDlx is consistently expressed in a spatially restricted domain in the presumptive ventral forebrain region of the neural plate that will give rise to the hypothalamus and the adenohypophysis. Our data support the notion that members of the Dlx gene family are part of a homeobox gene code in forebrain pattern formation and suggest that regional specification of the forebrain occurs at much earlier stages than previously thought. The homeobox gene cDlx may thus play a role in defining forebrain regional identity as early as gastrulation.