Study On Male Reproductive Dysfunction And Its Molecular Mechanism By Seipin Gene Mutation

Background:Male obesity has been found negatively associated with fertility, while the opposite condition of obesity, lipodystrophy, has not gained much attention in relation to male fertility.Although normal fertility in congenital generalized lipodystrophy (CGL) men has been noted in a recent study, no detailed data were given.In our study on a CGL2causal gene Seipin, we unexpectedly found complete male infertility in Seipin-deficient mice.This prompted us to re-examine the impact of lipodystrophy on male reproduction in humans and explore the potential molecular mechanisms in mice.Seipin is highly expressed in human brain, testis and adipose tissue. Lack of seipin in the brain has been linked to motor neuropathy and Silver syndrome, andloss in adipose tissue with severe lipodystrophy; its role in testis remains unknown.Methods and Findings:One male lipodystrophy patient with Seipin mutant was studied.His semen was collected and analyzed according to WHO Standards. A floxed Seipin mouse model was generated.mice with systemic, adipocyte-specific, and germ cell-specific deletion of Seipin gene were created by crossing with corresponding promoter driven-Cre transgenic mice. The reproductive function of these mice was assessed. Gene expression in testis and adipose tissue was analyzed by RT-PCR, Western blot and immunochemistry. Lipidomic and proteomics analysis was performed by mass spectrometry.Our study has found that:TheCGL2patient was found by obvious lipodystrophy. Compound mutations in Seipin were identified in this proband patient as well as his elder sister who showed similar lipodystrophy and hyperglycemia. The male patient showed teratozoospermia syndrome manifested as presence of bundled sperm in semen (two or more sperm connected to each other) which was nearly the same with those of infertile Seipin null mutant mice(S-KO). Analysis of conditional mouse mutants revealed that adipocyte-specific loss of Seipin(aS-KO) causes progressive lipodystrophy without affecting fertility, whereas loss of Seipin in germ cells(gS-KO) results in complete male infertility and teratozoospermia. Spermatids of the human patient and of mice devoid of Seipin in germ cells are morphologically abnormal with large ectopic lipid droplets and aggregate in dysfunctional clusters. The lipidomic analysis showed elevated levels of phosphatidic acid accompanied with an altered ratio of polyunsaturated to mono-unsaturated and saturated fatty acids appeared in S-KO and gS-KO mouse testes. And the proteomicsanalysis also indicates that impairedlipid homeostasis in the testes of S-KO mice. We conclude that the iipodystrophy caused by Seipin deficiency in adipose tissue only has no impact on male fertility. Instead,testicular but not adipose tissue-derived Seipin is essential for male fertility by modulating testicular phospholipid homeostasis.