Expression of elovl4 and fa2h with spermatogenic cell differentiation In the rat testis

Abstract

Rat spermatogenic cell membranes contain sphingolipids with nonhydroxy and 2-hydroxy very long chain (C24-32) PUFA. The biosynthesis of such fatty acids requires the expression of very long chain fatty acid elongases (Elovl4 for > C24) and a fatty acid 2- hydroxylase (Fa2h). In this study, mRNA levels of Elovl4and Fa2h were measured by qPCR in rat testis at different postnatal ages and in cells isolated from the seminiferous epithelium of adults. At early prepuberal ages (P14), Elovl4 was highly expressed while Fa2h mRNA was absent. Fa2h started to be detected at P25-30 and increased thereafter, while Elovl4mRNA levels decreased. The expression of both genes, but mainly Fa2h, was markedly reduced in adult testes that had been depleted of germ cells by mild hyperthermia. In isolated spermatogenic cells, both genes were expressed at lower levels in pachytene spermatocytes than in postmeiotic round and late spermatids. Interestingly, Sertoli cells had high Elovl4but lacked Fa2h mRNA. The Elovl4 protein was detected in spermatocytes from P21 to adulthood, when the protein was clearly observed in elongated spermatids. The Elovl4 enzyme was functional in germ cells, as these cells, in culture, were able to elongate [3H]20:4 to PUFA longer than C24. Our results underscore the presence of a well-timed, cell-specific regulation of Elovl4 and Fa2h in germ cells as differentiation proceeds.