Association study of protamine 2 (PRM2) gene polymorphism with male infertility in Chinese Han population

Paternal source of germ plasm determinants in the viviparous teleost, Gambusia holbrooki; dads do matter

The identity of germ cells, the progenitors of life, is thought to be acquired by two modes; either by maternal signals (preformed) or induced de novo from pluripotent cells (epigenesis) in the developing embryos. However, paternal roles seem enshrouded or completely overlooked in this fundamental biological process. Hence, we investigated the presence of germplasm transcripts in the sperm of Gambusia holbrooki, a live-bearing fish, demonstrating their presence and suggesting paternal contributions. Interestingly, not all germplasm markers were present (nanos1 and tdrd6) in the sperm, but some were conspicuous (dazl, dnd-α, piwi II, and vasa), indicating that the latter is required for establishing germ cell identity in the progeny, with a possible parent-specific role. Furthermore, there were also spatial differences in the distribution of these determinants, suggesting additional roles in sperm physiology and/or fertility. Our results support the hypothesis that dads also play a vital role in establishing the germ cell identity, especially in G. holbrooki, which shares elements of both preformation and induction modes of germline determination. This, coupled with its life history traits, makes G. holbrooki an excellent system for dissecting evolutionary relationships between the two germline determination modes, their underpinning mechanisms and ultimately the perpetuity of life.

Systematic review and meta-analysis of the genetic association between protamine polymorphism and male infertility

While several previous studies have proposed an association between male infertility and protamine polymorphism, the reported findings have shown some inconsistency. To evaluate the potential association between the two most common single nucleotide polymorphisms (rs2301365 and rs1646022) in protamine and male infertility, we performed a meta-analysis involving 2713 cases and 2086 controls from 15 published case-controlled studies. Overall, our analysis showed significant associations between the specific protamine single-nucleotide polymorphism (rs2301365) and male infertility, and this association was indicated by all of the models we tested. Subgroup analysis revealed significant associations with a Caucasian background, PCR sequence, population-based, case size of > 150 and case size of < 150 subgroups. Similarly, significant associations were found between rs1646022 and male infertility in the hospital population and case size of < 200 subgroups. However, trial sequential analysis showed that the number of patients in the study did not reach optimal information size. Further studies with larger sample sizes are now warranted to clarify the potential roles of the two protamine polymorphisms in the pathogenesis of male infertility. This may help us to understand the precise molecular mechanisms underlying the effect of protamines upon male infertility.

Polymorphisms of protamine genes contribute to male infertility susceptibility in the Chinese Han population

Protamine (PRM) plays important roles in the packaging of DNA within the sperm nucleus. To investigate the role of PRM1/2 and transition protein 1 (TNP1) polymorphisms in male infertility, 636 infertile men and 442 healthy individuals were recruited into this case-controlled study of the Chinese Han population, using MassARRAY technology to analyze genotypes. Our analysis showed that there were no significant differences between controls and infertile cases among the five single nucleotide polymorphisms identified in PRM1, PRM2 and TNP1 [rs737008 (G/A), rs2301365 (C/A), rs2070923 (C/A), rs1646022 (C/G) and rs62180545 (A/G)]. However, we found that the PRM1 and PRM2 haplotypes GCTGC, TCGCA and TCGCC exhibited significant protective effects against male infertility compared to fertile men, while TCGGA, GCTCC and TCGGC represented significant risk factors for spermatogenesis. Our data showed that rs737008 and rs2301365 in PRM1, and rs1646022 in PRM2, were significantly associated with male infertility and that gene–gene interaction played a role in male infertility. A linkage disequilibrium plot for the five SNPs showed that rs737008 was strongly linked with both rs2301365 and rs2070923. These findings are likely to help improve our understanding of the etiology of male infertility. Further studies should include a larger number of genes and SNPs, particularly growing critical genes; such studies will help us to unravel the effect of individual genetic factors upon male infertility.