[Quox 8, homeogene implicated in the establishment of dorso-ventral organization in vertebrates]

Quox 8 (= quail Msx 2) is an homeo box-containing gene of the msh family; we have been interested in the possible role of this gene in the patterning of somitic tissues around the neural tube. By the combined use of embryonic manipulations and in situ hybridization, we evidence that in embryonic day 2-6 avian embryos, Quox 8 expression in the dorsal mesenchyme depends (1) on the normal dorso-ventral polarization of the neural tube; (2) on tissue interactions between the dorsal neural tube and the overlying ectoderm. The somitic mesenchyme expressing Quox 8 gives rise to the spinous process of the vertebra. Experimental inhibition of Quox 8 expression results in the absence of the spinous process. Thus we conclude that Quox 8 is a step in the cascade of tissue interactions between the neural tube, the ectoderm and the mesenchyme, resulting in the patterning of the dorsal-most part of the vertebra.