Translocation of Tektin 3 to the equatorial segment of heads in bull spermatozoa exposed to dibutyryl cAMP and calyculin A

FSIP2 plays a role in the acrosome development during spermiogenesis

BACKGROUND

Loss-of-function mutations in FSIP2 result in multiple morphological abnormalities of the flagella in humans and mice. Intriguingly, a recent study found that FSIP2 might regulate the expression of acrosomal proteins, indicating that Fsip2 might be involved in acrosome development in mice. However, whether FSIP2 also function in acrosome biogenesis in humans is largely unknown, and the underlying mechanism of which is unexplored.

OBJECTIVE

Our objective was to reveal potential function of FSIP2 in regulating sperm acrosome formation.

METHODS

We performed whole exome sequencing on four asthenoteratozoospermic patients. Western blot analysis and immunofluorescence staining were conducted to assess the protein expression of FSIP2. Proteomics approach, liquid chromatography-tandem mass spectrometry and co-immunoprecipitation were implemented to clarify the molecules in acrosome biogenesis regulated by FSIP2.

RESULTS

Biallelic FSIP2 variants were identified in four asthenoteratozoospermic individuals. The protein expression of MUT-FSIP2 was sharply decreased or absent in vitro or in vivo. Interestingly, aside from the sperm flagellar defects, the acrosomal hypoplasia was detected in numerous sperm from the four patients. FSIP2 co-localised with peanut agglutinin in the acrosome during spermatogenesis. Moreover, FSIP2 interacted with proteins (DPY19L2, SPACA1, HSP90B1, KIAA1210, HSPA2 and CLTC) involved in acrosome biogenesis. In addition, spermatozoa from patients carrying FSIP2 mutations showed downregulated expression of DPY19L2, ZPBP, SPACA1, CCDC62, CCIN, SPINK2 and CSNK2A2.

CONCLUSION

Our findings unveil that FSIP2 might involve in sperm acrosome development, and consequently, its mutations might contribute to globozoospermia or acrosomal aplasia. We meanwhile first uncover the potential molecular mechanism of FSIP2 regulating acrosome biogenesis.

Identification of New Candidate Genes Related to Semen Traits in Duroc Pigs through Weighted Single-Step GWAS

Semen traits play a key role in the pig industry because boar semen is widely used in purebred and crossbred pigs. The production of high-quality semen is crucial to ensuring a good result in artificial insemination. With the wide application of artificial insemination in the pig industry, more and more attention has been paid to the improvement of semen traits by genetic selection. The purpose of this study was to identify the genetic regions and candidate genes associated with semen traits of Duroc boars. We used weighted single-step GWAS to identify candidate genes associated with sperm motility, sperm progressive motility, sperm abnormality rate and total sperm count in Duroc pigs. In Duroc pigs, the three most important windows for sperm motility-sperm progressive motility, sperm abnormality rate, and total sperm count-explained 12.45%, 9.77%, 15.80%, and 12.15% of the genetic variance, respectively. Some genes that are reported to be associated with spermatogenesis, testicular function and male fertility in mammals have been detected previously. The candidate genes CATSPER1, STRA8, ZSWIM7, TEKT3, UBB, PTBP2, EIF2B2, MLH3, and CCDC70 were associated with semen traits in Duroc pigs. We found a common candidate gene, STRA8, in sperm motility and sperm progressive motility, and common candidate genes ZSWIM7, TEKT3 and UBB in sperm motility and sperm abnormality rate, which confirms the hypothesis of gene pleiotropy. Gene network enrichment analysis showed that STRA8, UBB and CATSPER1 were enriched in the common biological process and participated in male meiosis and spermatogenesis. The SNPs of candidate genes can be given more weight in genome selection to improve the ability of genome prediction. This study provides further insight into the understanding the genetic structure of semen traits in Duroc boars.

Effects of Calyculin a on the Motility and Protein Phosphorylation in Frozen-Thawed Bull Spermatozoa

In this study, we examined the effects of calyculin A, a phosphatase inhibitor, on motility, protein phosphorylation, and the distribution of phospho-(Ser/Thr) PKA substrates in frozen-thawed bull spermatozoa that are actually used by most farmers for breeding. The data showed that calyculin A, which has been reported to have a positive effect on the motility of ejaculated fresh spermatozoa, distinctly decreased the motility of frozen-thawed bull spermatozoa even if a cell activator, such as caffeine, was present in the incubation medium and that the suppressive effect of calyculin A was dose-dependent and continued for at least 200 min. Immunoblot analyses revealed that de novo protein phosphorylation was not detected in spermatozoa exposed to caffeine or dbcAMP (a cell-permeable cAMP analog), while the addition of calyculin A to the medium brought about the appearance of several phosphorylated proteins at 50 kDa and 75 kDa, suggesting that 50 kDa and 75 kDa proteins, which were phosphorylated by activation of cAMP-dependent PKA, were not dephosphorylated and were accumulated in spermatozoa due to the suppression of calyculin A-sensitive protein phosphatases. Immunofluorescence microscopy revealed that calyculin A caused, alone or in conjunction with caffeine or dbcAMP, the accumulation of phospho-PKA substrates at the annulus, although caffeine or dbcAMP alone did not. This study suggested that calyculin A decreases the motility of frozen-thawed bull spermatozoa concomitant with the accumulation of phospho-(Ser/Thr) PKA substrates at the annulus of flagella.