Investigation of regulatory elements directing Dlx gene expression in the avian forebrain.

摘要

There are six known mammalian Distal-less type homeobox (Dlx) genes, arranged in three convergently transcribed pairs. Highly conserved cis-acting enhancer sequences have been identified in the Dlx1/2 and Dlx5/6 intergenic regions in zebrafish and mouse. Dlx3 and Dlx4 were originally thought not to be expressed in the forebrain of any vertebrate embryo; however expression of Dlx3 in the ventral forebrain of chick embryos has since been documented. Based on current models of Dlx gene evolution it is unclear whether forebrain enhancers have been retained in the Dlx3/4 locus throughout the course of avian evolution or whether they were acquired after the divergence of birds from other vertebrate lineages. It is difficult to evaluate forebrain enhancer conservation in the avian lineage with the current available genome sequence. This thesis describes the isolation of a genomic clone containing a partial Dlx3 gene and sequences downstream, and the development of assays to test enhancer activity in chicken and zebrafish embryos.