Expression of class I homeobox genes in fetal and adult murine skin.

We examined the expression patterns of several class I homeobox genes in mouse fetal and adult skin. All the genes of the Hox-B locus, except Hoxb-1, are expressed in skin from murine fetuses of 17 and 18 d gestation, at which time the epidermis is undergoing stratification and differentiation. The amount of individual Hox gene message varies considerably, but expression of all genes is detectable by RNase protection except Hoxb-1, which could not be detected even by the reverse transcription-polymerase chain reaction (RT-PCR) assay. Homeobox gene expression in skin is not confined to the Hox-B locus; the paralogous genes Hoxa-4, -b-4, -c-4, and -d-4 are all expressed. The amount of Hoxb-4, -b-2, and -c-4 message in skin is relatively constant from the earliest gestational day examined (day 16) through birth at day 19. Expression of several homeobox genes is also seen in adult skin.