Localization and regulation of expression of the FAR-17A gene in the hamster flank organs.

A quantitative in situ hybridization study was carried out to determine the precise localization and androgen regulation of the flank organ regulated (FAR-17A) mRNA expression in the different cellular components of the hamster flank organs. Although FAR-17A mRNA was highly expressed in the epithelial cells of the sebaceous glands, it was also found in the outer root sheath of the hair follicles and in melanocytes. The changes in FAR-17A mRNA levels, in the size of the flank organ and sebaceous gland areas as well as in the weight of the seminal vesicles and prostate, were compared following castration and after 5alpha-dihydrotestosterone treatment. FAR-17A mRNA levels were already significantly decreased 1 d after castration, in parallel with a concomitant decrease in the number of labeled cells with the FAR-17A probe. A maximal decrease was found 7 d after castration. The other parameters were significantly reduced later. After 7 d of treatment with dihydrotestosterone, all values returned to those found in intact animals. Similar stimulatory effects on these parameters were observed after treatment with the adrenal sex steroid precursor dehydroepiandrosterone. These data show that all of the components of the flank organs (sebaceous glands, hair follicles, and melanocytes) express the flank organ regulated (17A) type gene (FAR-17A) gene and that its expression is stimulated by treatment with either dihydrotestosterone or dehydroepiandrosterone. Moreover, FAR-17A mRNA levels respond to androgen stimulation more rapidly than the standard morphologic parameters, revealing that the FAR-17A gene could be a more sensitive and cell specific marker to study the mechanisms of androgen action in the skin.