Genes involved in intercellular signal transduction during melanocyte differentiation in the mouse.

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A signal transduction mechanism in the cell membrance, which receive information from the cellular environment and transfers it to the site of cellular function, has been demonstrated in various cell types. At the final step of melanocyte differentiation in mouse hair follicles, the cells produce melanin. The type of melanin they produce is, however, determined by the tissue. environment of hair follicles. In wild-type mice, melanocytes located in hair bulbs synthesize eumelanin at the beginning of hair growth. They subsequently produce pheomelanin and finally produce eumelanin again. Therefore, the hair is characterized by a subterminal band of yellow, with the rest of it displaying black. This characteristic is called the agouti pattern and is known to be determined by the wild-type allele, A__-, at the a__-(agouti) locus, which is considered to function in the dermal cells. By using an organ culture method, we have demonstrated that the product of the a__- locus (A factor) blocks th … More e action of MSH (melanocyte stimulating hormone) at the・MSH receptor site, and modifies the pathway of melanin biosynthesis. An attempt was made in the present study to clone cDNA for the A factor.Mice homozygous for a__- allele were injected with skin homogenate from the mouse, genotype A^y/a__-, which constitutively produces the A factor. Polyclonal as well as monoclonal antibodies were prepared from these mice. Immunohistochemical localization of the antigen revealed that cells scatterd in dermis were positive. Thses cells, presumably mast cells, ate expected to be the site of the gene action of the a__- locus from the results of previous studies. A cDNA library was constructed from poly (A)^+mRNA from the mouse skin with the genotype A^y/a using gtll vector, and screened with the antibodies. Two clones, A^y11 (2.8 kbp)and A^y9(750 bp), were isolated. Results of the in situ hybridization by using the cDNAs as probes demonstrated that the mRNA hybridized with the A^y11 was located in the dermal cells (presumably mast cells) and that the site of the transcription for A^y9 was melanocyte. Therefore, it is likely that the A^y11 is a cDNA for the A factor and that the A^y9 is a cDNA for a product of secondary gene action induced by the A factor. Less