Three promoters PII, PI.f, and PI.tr direct the expression of aromatase (cyp19) gene in male rat germ cells

Abstract

Aromatase is the key enzyme responsible for the irreversible transformation of androgens into estrogens. It is encoded by the cyp19 gene and is expressed in the mammalian testis under the control of the proximal promoter PII. Since both somatic and germ cells contain a biologically active aromatase, we looked for the existence of other promoters that may direct the expression of aromatase in adult rat germ cells. Besides the promoter II, we have shown the presence of transcripts derived from the brain promoter PI.f in spermatogonia-preleptotene spermatocytes (G-PL), pachytene spermatocytes (PS), and round spermatids (RS). A new aromatase cDNA has been isolated by 5 0 -rapid amplification of cDNA ends that we named I.tr (testis rat). The I.tr transcripts are found in all the testicular cell populations studied with a greater expression in PS. Because of the utilization of these three promoters in the adult rat testis, we studied their putative involvement according to the age. At 10 days, aromatase expression was very low and then strongly increased between 10 and 20 days, with a preferential activation of PII and PI.tr. Transcripts coming from PI.f were found starting from 20 days onwards. The new promoter PI.tr, localized between promoters PI.f and PII, is devoid of a TATA box but contains a transcriptional initiator (Inr) and putative regulatory sequences. Therefore, the identification of the specific trans-activating factors should bring some enlightenments to understand the regulation of these three promoters in germ cells especially according to their stage of development.

Oestrogens and spermatogenesis

“…The presence of aromatase mRNA has been reported in gonocytes, spermatogonia as well as in preleptotene spermatocytes (Silandre et al 2007). However, in purified myoid cells, we were unable to detect any aromatase transcript by RT-PCR and therefore, the aromatase gene is present in all stages of germ cell development (figure 2) so far studied .…”

Testis morphology in rats chronically treated with letrozole, an aromatase inhibitor

“…P450arom is the member of the cytochrome P450 gene superfamily, and is a product of transcription of a single copy of the Cyp19 gene. In humans, this is located on chromosome 15 [13][14][15], in rats on chromosome 8, and in mice on chromosome 9 [16]. The enzyme is a microsomal complex composed of two proteins: specific heme-glycoprotein cytochrome P450 aromatase, which contains a steroid binding pocket, and ubiquitous NADPH-cytochrome P450 reductase [13,14].…”

Male germ cells of the Pacific oysterCrassostrea gigas: flow cytometry analysis, cell sorting and molecular expression

“…The isolation procedure developed in our study was derived from techniques performed in trout (Loir 1994) and rat (Com et al 2003;Silandre et al 2007) to isolate subpopulations of germ cells. One of the final goals of our study is to obtain purified cell suspensions in order to develop homologous functional bioassays in oyster.…”

“…Molecular characterization of the different cell populations present in gonadal tubules in oyster, as in seminiferous tubules in mammals, represents a challenge, due to the multitude of germinal cell types and somatic cells present in cell suspensions issued from gonad dissection. Numerous strategies have been developed in vertebrates to isolate these cell populations, among which a bovine serum albumin (BSA) density gradient allowed suspensions of spermatogonia (Com et al 2003), pachytene spermatocytes and round spermatids (Silandre et al 2007) to be obtained in rat.…”