RETINOIC ACID AND MOUSE SKIN MORPHOGENESIS .1. EXPRESSION PATTERN OF RETINOIC ACID RECEPTOR GENES DURING HAIR VIBRISSA FOLLICLE, PLANTAR, AND NASAL GLAND DEVELOPMENT

The spatial and temporal expression of the nuclear retinoic acid recep tors alpha, beta, ana gamma (RAR-alpha,beta, and gamma) was compared b y in situ hybridization during hair vibrissa follicle and nasal and pl antar eccrine gland morphogenesis in mouse embryo. The RAR-alpha and R AR-gamma above control level during both hair vibrissa and plantar gla nd morphogenesis. By contrast, during nasal gland formation (12.5- to 15.5-d embryos), the RAR-beta signal reaches a high level in mesenchym al cells, whereas the RAR-alpha transcripts are present in both epithe lial and mesenchymal cells. These results suggest a role for RAR-alpha and RAR-gamma in the epidermal-dermal interactions that lead to hair follicle and plantar gland morphogenesis, whereas the nasal gland deve lopment implies RAR-alpha and RAR-beta gene expression. This should be correlated with the expression of the RAR-beta gene that was previous ly shown to be linked to the RA-induced glandular metaplasia of hair v ibrissa follicles. transcripts are abundant in the dermal papilla cell s of the hair vibrissa when these cells elicit epidermal hair placode (12.5-d embryos) and hair follicle (13.5-d embryos) formation. Both th ese transcripts are also abundant in the dermal cells of the plantar f oot pad at the initiation stage (17.5-d embryos) of glandular morphoge nesis. In epidermal cells, the distribution of RAR-gamma transcripts i ncreases in parallel with hair vibrissa follicle and sweat gland diffe rentiation, and thus may be part of the epidermal response to the derm al instructions. The RAR-beta signal is barely