EXPRESSION OF THE HOX-2.2 HOMEOBOX GENE IN MURINE EMBRYONIC EPIDERMIS

The expression of the Hox 2.2 gene was studied in mouse fetal skin by in situ hybridization with an anti-sense RNA probe derived from the homeobox region of this gene. In contrast to the expression of Hox 2.2 in spinal cord, which is strongest in 11-day embryos, and is greatly diminished by day 14 and day 17, the signal for Hox 2.2 in skin could be not be detected in 11-day epidermis, was barely detectable on day 14, became strong on day 17, and decreased in new-born animals (day 19). RNase protection assays using Hox 2.2 homeobox-containing and 3' flanking region probes confirmed that the signals detected in 17-day fetal skin by in situ hybridization represent Hox 2.2 transcripts, and that the message is expressed throughout the day 15 to day 18 period during which the epidermis is undergoing terminal differentiation. RNase protection analysis also revealed two alternatively spliced forms of the Hox 2.2 mRNA are present throughout fetal skin development. Northern gel analysis of 17-day fetal skin using a Hox 2.2 homeobox-containing probe at high stringency showed two bands of 1.6 and 1.9 kb, respectively. The 1.9 kb band was greatly enhanced by hybridization at reduced stringency, suggesting the expression of additional homeobox genes with homology to Hox 2.2. These results suggest that the Hox 2.2 homeobox gene plays a role in epidermal development.