Specification of Jaw Subdivisions by <i>Dlx</i> Genes

TLDR

Vertebrate success depends on jaw acquisition and modification, which arise from branchial arches that exhibit proximodistal polarity and may have evolved through changes in Dlx expression. The study aims to investigate how Dlx5 and Dlx6 expression patterns specify skeletal element identity within branchial arches. The authors examined mice deficient in Dlx5 and Dlx6, homeobox genes expressed distally but not proximally within the arches. Loss of Dlx5/6 causes lower jaws to transform into upper jaws, supporting the idea that nested Dlx expression patterns pattern the proximodistal axes of the arches.

Abstract

The success of vertebrates was due in part to the acquisition and modification of jaws. Jaws are principally derived from the branchial arches, embryonic structures that exhibit proximodistal polarity. To investigate the mechanisms that specify the identity of skeletal elements within the arches, we examined mice lacking expression of Dlx5 and Dlx6 , linked homeobox genes expressed distally but not proximally within the arches. Dlx5/6 –/– mutants exhibit a homeotic transformation of lower jaws to upper jaws. We suggest that nested Dlx expression in the arches patterns their proximodistal axes. Evolutionary acquisition and subsequent refinement of jaws may have been dependent on modification of Dlx expression.