Distal-less

In evolutionary developmental biology, DLX is a family of homeodomain transcription factors which are related to the Drosophila distal-less (Dll) gene.

Distal-less itself, and its homologues, is involved in limb development in most of the major phyla, including vertebrates — suggesting that it was involved in appendage growth in an early bilaterial ancestor.

The family has been related to a number of developmental features. The family seems to be well preserved across species.

Known members of the family include DLX1 to DLX6. They form two-gene clusters (bigene clusters) with each other. There are DLX1-DLX2, DLX3-DLX4, DLX5-DLX6 clusters in vertebrates. Each of those are linked to a specific Hox gene cluster. In higher fishes, like Zebrafish, there are a couple of additional DLX genes, DLX5 and DLX8. In zebrafish the orthologous genes to vertebrate DLX5-DLX6 are DLX4 and DLX6, which form a bigene cluster in zebrafish. These additional genes are not linked with each other, or any other DLX gene.

DLX4, DLX7, DLX8 and DLX9 are the same gene in vertebrates. They're named differently, because every time the same gene was found, the researchers thought they had found a new gene.

DLX genes are involved in craniofacial morphogenesis and the tangential migration of interneurons from the subpallium to the pallium during vertebrate brain development. It has been suggested that DLX promotes the migration of interneurons by repressing a set of proteins that are normally expressed in terminally differentiated neurons and act to promote the outgrowth of dendrites and axons. Mice lacking DLX1 exhibit electrophysiological and histological evidence consistent with delayed-onset epilepsy.

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