Cihox5, a new Ciona intestinalis Hox-related gene, is involved in regionalization of the spinal cord.

In this paper we report the cloning, sequence and expression analysis of a new Ciona intestinalis hox gene. On the basis of sequence comparison with mammalian and Amphioxus homologues, we called this gene Cihox5. Northern blot analysis reveals a single transcript of about 1.3 kb in length, that is present from neurula until larva stage. Whole-mount in situ hybridization shows restricted expression of this gene in putative blood cells precursors and in a regional domain of the spinal chord. Expression in the spinal cord is attributed to ependymal cells. This result implies a role for this gene in primitive regionalization of spinal cord along the anteroposterior axis in the absence of neuronal bodies.