Elovl4 and Fa2h expression during rat spermatogenesis: a link to the very-long-chain PUFAs typical of germ cell sphingolipids.

The sphingolipids (SLs) of rodent spermatogenic cells (spermatocytes, spermatids) and spermatozoa contain nonhydroxylated and 2-hydroxylated versions of very-long-chain (C26-C32) PUFAs (n-V and h-V, respectively) not present in Sertoli cells (SCs). Here, we investigated the expression of selected fatty acid elongases [elongation of very-long-chain fatty acid protein (Elovl)], with a focus on Elovl4, and a fatty acid 2-hydroxylase (Fa2h) in rat testes with postnatal development and germ cell differentiation. Along with Elovl5 and Elovl2, Elovl4 was actively transcribed in the adult testis. Elovl4 mRNA levels were high in immature testes and SCs, though the protein was absent. The Elovl4 protein was a germ cell product. All cells under study elongated [3H]arachidonate to tetraenoic and pentaenoic C24 PUFA, but only germ cells produced C26-C32 PUFAs. Spermatocytes displayed the highest Elovl4 protein levels and enzymatic activity. Fa2h mRNA was produced exclusively in germ cells, mostly round spermatids. As a protein, Fa2h was mainly concentrated in late spermatids, in the step of spermiogenesis in which they elongate and their heads change shape. The expression of Elovl4 and Fa2h thus correlate with the abundance of n-Vs and h-Vs in the SLs of rat spermatocytes and spermatids, respectively.