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Red deer stags produce an androgen-dependent mane of long hairs only in the breeding season; in the non-breeding season, when circulating androgen levels are low, the neck hair resembles the rest of the coat. This study was designed to determine whether androgen receptors are present in deer follicles throughout the year or only in the mane (neck) follicles when circulating testosterone levels are high in the breeding season. Although androgens regulate much human hair growth the mechanisms are not well understood; they are believed to act on the hair follicle epithelium via the mesenchyme-derived dermal papilla. The location of androgen receptors in the follicle was investigated by immunohistochemistry and androgen binding was measured biochemically in cultured dermal papilla cells derived from mane and flank follicles during the breeding season and from neck follicles during the non-breeding season. Immunohistochemistry of frozen skin sections using a polyclonal antibody to the androgen receptor localised nuclear staining only in the dermal papilla cells of mane follicles. Saturation analysis assays of 14 primary dermal papilla cell lines using [(3)H]-mibolerone demonstrated high-affinity, low-capacity androgen receptors were present only in mane (breeding season neck) cells; competition studies with other steroids confirmed the specificity of the receptors. Androgen receptors were not detectable in cells from either the breeding season flank nor the non-breeding season neck follicles. The unusual biological model offered by red deer of androgen-dependent hair being produced on the neck in the breeding, but not the non-breeding season, has allowed confirmation that androgen receptors are required in follicle dermal papilla cells for an androgen response; this concurs with previous human studies. In addition, the absence of receptors in the non-breeding season follicles demonstrates that receptors are not expressed unless the follicle is responding to androgens. Androgen receptors may be induced in mane follicles by seasonal changes in circulating hormone(s).

Although analysis of luciferase activity using luminescence imaging has provided new insights into the dynamic regulation of gene expression in living tIssues, studies in vitro have relied on stably transfected clonal cell lines, limiting the choice of cell type and species, or DNA microinjection, which is arduous and highly selective. We report here the first use of a recombinant adenovirus in which the firefly luciferase reporter gene was regulated by the prolactin gene promoter, to study temporal dynamics of promoter activity. This vector was used to infect the pituitary GH3 cell line, and also primary cultures of Syrian hamster pituitary cells. We show that adenovirally transduced cells retained normal regulation of the promoter-reporter transgene by appropriate signals. Furthermore, microscopic imaging studies indicated that both clonal and primary pituitary cells were transduced efficiently, giving readily detectable luminescence signals in real-time over long periods. Finally, analysis of single-cell expression patterns indicated that prolactin promoter activity was highly dynamic with pulses in gene expression, revealing that the transcriptional instability seen in clonal cells is a feature of normal pituitary cells. Adenoviral vectors offer a valuable tool for studies of gene regulation where conventional transgenesis and clonal cell lines are not available.