Aromatase messenger RNA is derived from the proximal promoter of the aromatase gene in Leydig, Sertoli, and germ cells of the rat testis

It has long been recognized that individual cell types within the testes po ssess the capacity to synthesize estrogen. A number of studies on different species have demonstrated that the levels of aromatase expression and the patterns of regulation are distinct between the different cell types of the testes. Whereas a variety of promoters have been shown to contribute to th e patterns of aromatase expression in different cell lineages, studies usin g ovarian RNA, testis RNA, and Leydig cell tumor lines have demonstrated th at the same promoter (promoter II) was used in each. Recent experiments usi ng potent aromatase inhibitors or analysis of animals in which the genes en coding the estrogen receptor-alpha (ER-alpha) or the aromatase, P450, are d efective, have confirmed the importance of local estrogen formation in norm al testicular function. In order to permit experiments to identify the elem ents controlling aromatase expression in the individual cell compartments o f the testes, we prepared RNA from purified preparations of Leydig, Sertoli , and germ cells. Using specific oligonucleotide primers, the sites of init iation of the aromatase mRNA were determined using rapid amplification of c DNA ends (RACE) and nucleotide sequence analysis of the resulting cDNA frag ments. Our results indicate that aromatase mRNA is derived from the proxima l promoter (P11) of the aromatase gene in each of the major cell types of t he rat testes.