Androgen receptor is expressed in both X- and Y-carrier human spermatozoa

Genetic resistance to DEHP-induced transgenerational endocrine disruption

Di(2-ethylhexyl)phthalate (DEHP) interferes with sex hormones signaling pathways (SHP). C57BL/6J mice prenatally exposed to 300 mg/kg/day DEHP develop a testicular dysgenesis syndrome (TDS) at adulthood, but similarly-exposed FVB/N mice are not affected. Here we aim to understand the reasons behind this drastic difference that should depend on the genome of the strain. In both backgrounds, pregnant female mice received per os either DEHP or corn oil vehicle and the male filiations were examined. Computer-assisted sperm analysis showed a DEHP-induced decreased sperm count and velocities in C57BL/6J. Sperm RNA sequencing experiments resulted in the identification of the 62 most differentially expressed RNAs. These RNAs, mainly regulated by hormones, produced strain-specific transcriptional responses to prenatal exposure to DEHP; a pool of RNAs was increased in FVB, another pool of RNAs was decreased in C57BL/6J. In FVB/N, analysis of non-synonymous single nucleotide polymorphisms (SNP) impacting SHP identified rs387782768 and rs29315913 respectively associated with absence of the Forkhead Box A3 (Foxa3) RNA and increased expression of estrogen receptor 1 variant 4 (NM_001302533) RNA. Analysis of the role of SNPs modifying SHP binding sites in function of strain-specific responses to DEHP revealed a DEHP-resistance allele in FVB/N containing an additional FOXA1-3 binding site at rs30973633 and four DEHP-induced beta-defensins (Defb42, Defb30, Defb47 and Defb48). A DEHP-susceptibility allele in C57BL/6J contained five SNPs (rs28279710, rs32977910, rs46648903, rs46677594 and rs48287999) affecting SHP and six genes (Svs2, Svs3b, Svs4, Svs3a, Svs6 and Svs5) epigenetically silenced by DEHP. Finally, targeted experiments confirmed increased methylation in the Svs3ab promoter with decreased SEMG2 persisting across generations, providing a molecular explanation for the transgenerational sperm velocity decrease found in C57BL/6J after DEHP exposure. We conclude that the existence of SNP-dependent mechanisms in FVB/N inbred mice may confer resistance to transgenerational endocrine disruption.

Androgen receptor binding to an androgen-responsive element in the promoter of the Srsf4 gene inhibits its expression in mouse Sertoli cells

The serine/arginine-rich splicing actor 4 (SRSF4) is essential for pre-mRNA splicing and can influence alternative-splice-site choice. Little is known about the specific function of this gene in the reproductive system, although a recent study identified a SRSF4 polymorphism significantly associated with a decreased risk of non-obstructive azoospermia in Chinese men. We previously found that the expression of Srsf4 was up-regulated in the testes of Sertoli-cell-selective androgen receptor knockout (S-Ar(-/y)) mice compared to wild-type mice using digital gene expression analysis. In this study, we confirmed and extended the selective gene expression data: SRSF4 was mainly located in the nucleus of Sertoli cells, and Srsf4 expression in the Sertoli-cell-derived cell line TM4 is down-regulation by testosterone. Moreover, androgen receptor directly binds the androgen-responsive element of the Srsf4 promoter. Taken together, these results demonstrate that Srsf4 is a direct downstream target of the androgen receptor in mouse Sertoli cells.

Androgen receptors in the bonnethead, Sphyrna tiburo: cDNA cloning and tissue-specific expression in the male reproductive tract

As demonstrated in past studies, androgens appear to play critical roles in regulating reproduction in male sharks. However, little is known about the cell-specific actions of androgens in these fishes. To address this, this study examined androgen targets in reproductive organs of a seasonally reproducing shark, the bonnethead (Sphyrna tiburo). A partial bonnethead AR cDNA clone was isolated and found to exhibit strong homology with known vertebrate ARs. Using RT-PCR and in situ hybridization, AR was found to be expressed in multiple cell types in the male bonnethead testis (premeiotic germ cells, Leydig-like interstitial cells, Sertoli cells, peritubular myoid cells, and mature spermatozoa) and gonadal ducts (stromal cells, luminal epithelial cells, mature spermatozoa). Furthermore, AR expression in these organs was found to vary temporally in relation to the seasonal reproductive cycle. Based on immunocytochemistry, the presence of AR protein in male bonnethead reproductive organs was largely consistent with patterns of AR gene expression with the single exception of mature spermatozoa, which exhibited consistently strong mRNA expression but only inconsistent and weak AR protein immunoreactivity. These results suggest important roles for androgens in regulating germ cell proliferation, hormone production, spermatid elongation, spermiation, and gonadal duct function in male bonnetheads. In addition, high abundance of AR mRNA in bonnethead spermatozoa suggest the potential for de novo protein synthesis following spermiation/copulation and/or a role for AR mRNA in early embryonic development, both of which have been proposed to explain the occurrence of mRNA transcripts in spermatozoa from various vertebrates.

Autocrine regulation of human sperm motility by tachykinins

BACKGROUND

We examined the presence and function of tachykinins and the tachykinin-degrading enzymes neprilysin (NEP) and neprilysin-2 (NEP2) in human spermatozoa.

METHODS

Freshly ejaculated semen was collected from forty-eight normozoospermic human donors. We analyzed the expression of substance P, neurokinin A, neurokinin B, hemokinin-1, NEP and NEP2 in sperm cells by reverse-transcriptase polymerase chain reaction (RT-PCR), western blot and immunocytochemistry assays and evaluated the effects of the neprilysin and neprilysin-2 inhibitor phosphoramidon on sperm motility in the absence and presence of tachykinin receptor-selective antagonists. Sperm motility was measured using WHO procedures or computer-assisted sperm analysis (CASA).

RESULTS

The mRNAs of the genes that encode substance P/neurokinin A (TAC1), neurokinin B (TAC3), hemokinin-1 (TAC4), neprilysin (MME) and neprilysin-2 (MMEL1) were expressed in human sperm. Immunocytochemistry studies revealed that tachykinin and neprilysin proteins were present in spermatozoa and show specific and differential distributions. Phosphoramidon increased sperm progressive motility and its effects were reduced in the presence of the tachykinin receptor antagonists SR140333 (NK1 receptor-selective) and SR48968 (NK2 receptor-selective) but unmodified in the presence of SR142801 (NK3 receptor-selective).

CONCLUSION

These data show that tachykinins are present in human spermatozoa and participate in the regulation of sperm motility. Tachykinin activity is regulated, at least in part, by neprilysins.