HOX HOMEOBOX GENES EXHIBIT SPATIAL AND TEMPORAL CHANGES IN EXPRESSIONDURING HUMAN SKIN DEVELOPMENT

The spatial and temporal deployment of HOX homeobox genes along the sp inal axis and in limb buds during fetal development is a key program, in embryonic pattern formation. Although we have previously reported t hat several of the HOX homeobox genes are expressed during murine skin development, there is no information about developmental expression o f HOX genes in human skin. We have now used reverse transcriptase poly merase chain reaction, in conjunction with a set of degenerate oligonu cleotide primers, to identify a subset of HOX genes that are expressed during human fetal skin development. In situ hybridization analyses d emonstrated that there were temporal and spatial shifts in expression of these genes. Strong HOXA4 expression was detected in the basal cell layers of 10 wk fetal epidermis and throughout the epidermis and derm is of 17 wk skin, whereas weak signal was present in the granular laye r of newborn and adult skin. The expression patterns of HOXA5 and HOXA 7 were similar, but their expression was weaker, In sib hybridization analysis also revealed strong HOXC4 and weaker HOXB7 expression throug hout fetal development, whereas HOXB4 was expressed at barely detectab le levels, Differential HOX gene expression was also observed in devel oping hair follicles, and sebaceous and sweat glands, None of the HOX genes examined were detected in the adult dermis.