Hoxa4 expression in developing mouse hair follicles and skin

We have examined the expression of the Hoxa4 gene in embryonic vibrissae an d developing and cycling postnatal pelage hair follicles by digoxigenin-bas ed in situ hybridization. Hoxa4 expression is first seen in E13.5 vibrissae throughout the follicle placode, From E15.5 to E18.5 its expression is res tricted to Henle's layer of the inner root sheath. Postnatally, Hoxa4 expre ssion is observed at all stages of developing pelage follicles, from PO to P4. Sites of expression include both inner and outer root sheaths, matrix c ells, and the interfollicular epidermis. Hoxa4 is not expressed in hair fol licles after P4. Hoxb4, however, is expressed both in developing follicles at P2 and in catagen at P19, suggesting differential expression of these tw o paralogous genes in the hair follicle cycle. (C) 2000 Elsevier Science Ir eland Ltd. All rights reserved.