TMEM225: a possible protein phosphatase 1γ2 (PP1γ2) regulator localizes to the equatorial segment in mouse spermatozoa

TMEM225 Is Essential for Sperm Maturation and Male Fertility by Modifying Protein Distribution of Sperm in Mice

Nonobstructive azoospermia is the leading cause of male infertility. Abnormal levels of transmembrane protein 225 (TMEM225), a testis-specific protein, have been found in patients with nonobstructive azoospermia, suggesting that TMEM225 plays an essential role in male fertility. Here, we generated a Tmem225 KO mouse model to explore the function and mechanism of TMEM225 in male reproduction. Male Tmem225 KO mice were infertile. Surprisingly, Tmem225 deletion did not affect spermatogenesis, but TMEM225-null sperm exhibited abnormalities during epididymal maturation, resulting in reduced sperm motility and an abnormal hairpin-loop configuration. Furthermore, proteomics analyses of cauda sperm revealed that signaling pathways related to mitochondrial function, the glycolytic pathway, and sperm flagellar morphology were abnormal in Tmem225 KO sperm, and spermatozoa lacking TMEM225 exhibited high reactive oxygen species levels, reduced motility, and flagellar folding, leading to typical asthenospermia. These findings suggest that testicular TMEM225 may control the sperm maturation process by regulating the expression of proteins related to mitochondrial function, glycolysis, and sperm flagellar morphology in epididymal spermatozoa.

The UFMylated ribosome-recognition protein SAYSD1 is predominantly expressed in spermatids but is dispensable for fertility in mice

SAYSVFN domain-containing protein 1 (SAYSD1) is an evolutionarily conserved membrane protein that has recently been identified as a ubiquitin-fold modifier 1 (UFM1)-conjugated ribosome-recognition protein that plays a critical role in translocation-associated quality control (TAQC). However, its expression and roles in mammals in vivo remain largely unknown. We found that SAYSD1 is predominantly expressed in round and elongating spermatids and localizes in the endoplasmic reticulum (ER) of mouse testes, but not in differentiated spermatozoa. Mice deficient in Saysd1 developed normally post-partum. Furthermore, Saysd1-deficient mice were fertile, with no apparent differences in sperm morphology or motility compared with wild-type sperm, although the cauda epididymis contained slightly less sperm. Expression of the ER stress markers spliced X-box binding protein 1s (XBP1s) and CCAAT/enhancer binding protein (C/EBP)-homologous protein (CHOP) in the testes was comparable between Saysd1-deficient and wild-type mice. These results suggested that SAYSD1 is involved in sperm production in mice but is dispensable for their development and fertility.

Disruption of protein phosphatase 1 complexes with the use of bioportides as a novel approach to target sperm motility

OBJECTIVE

To design protein phosphatase 1 (PP1)-disrupting peptides covalently coupled to inert cell-penetrating peptides (CPPs) as sychnologically organized bioportide constructs as a strategy to modulate sperm motility.

DESIGN

Experimental study.

SETTING

Academic research laboratory.

PATIENT(S)/ANIMAL(S)

Normozoospermic men providing samples for routine analysis and Holstein Frisian bulls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Effect of the bioportides on the activity and interactions of PP1γ2-a PP1 isoform expressed exclusively in testicular germ cells and sperm-and on sperm vitality and motility.

RESULT(S)

PP1-disrupting peptides were designed based on the sequences from: 1) a sperm-specific PP1 interactor (A kinase anchor protein 4); and 2) a PP1 inhibitor (protein phosphatase inhibitor 2). Those sequences were covalently coupled to inert CPPs as bioportide constructs, which were successfully delivered to the flagellum of sperm cells to induce a marked impact on PP1γ2 activity and sperm motility. Molecular modeling studies further facilitated the identification of an optimized PP1-binding sequence and enabled the development of a modified stop-sperm bioportide with reduced size and increased potency of action. In addition, a bioportide mimetic of the unique 22-amino acid C-terminus of PP1γ2 accumulated within spermatozoa to significantly reduce sperm motility and further define the PP1γ2-specific interactome.

CONCLUSION(S)

These investigations demonstrate the utility of CPPs to deliver peptide sequences that target unique protein-protein interactions in spermatozoa to achieve a significant impact upon spermatozoa motility, a key prognostic indicator of male fertility.

Transcriptome profiling of porcine testis tissue reveals genes related to sperm hyperactive motility

BACKGROUND

Sperm hyperactive motility has previously been shown to influence litter size in pigs, but little is known about the underlying biological mechanisms. The aim of this study was to use RNA sequencing to investigate gene expression differences in testis tissue from Landrace and Duroc boars with high and low levels of sperm hyperactive motility. Boars with divergent phenotypes were selected based on their sperm hyperactivity values at the day of ejaculation (day 0) (contrasts (i) and (ii) for Landrace and Duroc, respectively) and on their change in hyperactivity between day 0 and after 96 h liquid storage at 18 °C (contrast (iii)).

RESULTS

RNA sequencing was used to measure gene expression in testis. In Landrace boars, 3219 genes were differentially expressed for contrast (i), whereas 102 genes were differentially expressed for contrast (iii). Forty-one differentially expressed genes were identified in both contrasts, suggesting a functional role of these genes in hyperactivity regardless of storage. Zinc finger DNLZ was the most up-regulated gene in contrasts (i) and (iii), whereas the most significant differentially expressed gene for the two contrasts were ADP ribosylation factor ARFGAP1 and solute carrier SLC40A1, respectively. For Duroc (contrast (ii)), the clustering of boars based on their gene expression data did not reflect their difference in sperm hyperactivity phenotypes. No results were therefore obtained for this breed. A case-control analysis of variants identified in the Landrace RNA sequencing data showed that SNPs in NEU3, CHRDL2 and HMCN1 might be important for sperm hyperactivity.

CONCLUSIONS

Differentially expressed genes were identified in Landrace boars with high and low levels of sperm hyperactivity at the day of ejaculate collection and high and low change in hyperactivity after 96 h of sperm storage. The results point towards important candidate genes, biochemical pathways and sequence variants underlying sperm hyperactivity in pigs.

Signaling Enzymes Required for Sperm Maturation and Fertilization in Mammals

In mammals, motility and fertilizing ability of spermatozoa develop during their passage through the epididymis. After ejaculation, sperm undergo capacitation and hyperactivation in the female reproductive tract - a motility transition that is required for sperm penetration of the egg. Both epididymal initiation of sperm motility and hyperactivation are essential for male fertility. Motility initiation in the epididymis and sperm hyperactivation involve changes in metabolism, cAMP (cyclic adenosine mono-phosphate), calcium and pH acting through protein kinases and phosphatases. Despite this knowledge, we still do not understand, in biochemical terms, how sperm acquire motility in the epididymis and how motility is altered in the female reproductive tract. Recent data show that the sperm specific protein phosphatase PP1γ2, glycogen synthase kinase 3 (GSK3), and the calcium regulated phosphatase calcineurin (PP2B), are involved in epididymal sperm maturation. The protein phosphatase PP1γ2 is present only in testis and sperm in mammals. PP1γ2 has a isoform-specific requirement for normal function of mammalian sperm. Sperm PP1γ2 is regulated by three proteins - inhibitor 2, inhibitor 3 and SDS22. Changes in phosphorylation of these three inhibitors and their binding to PP1γ2 are involved in initiation and activation of sperm motility. The inhibitors are phosphorylated by protein kinases, one of which is GSK3. The isoform GSK3α is essential for epididymal sperm maturation and fertility. Calcium levels dramatically decrease during sperm maturation and initiation of motility suggesting that the calcium activated sperm phosphatase (PP2B) activity also decreases. Loss of PP2B results in male infertility due to impaired sperm maturation in the epididymis. Thus the three signaling enzymes PP1γ2, GSK3, and PP2B along with the documented PKA (protein kinase A) have key roles in sperm maturation and hyperactivation. Significantly, all these four signaling enzymes are present as specific isoforms only in placental mammals, a testimony to their essential roles in the unique aspects of sperm function in mammals. These findings should lead to a better biochemical understanding of the basis of male infertility and should lead to novel approaches to a male contraception and managed reproduction.

Expression analysis of a panel of cancer-testis antigens in bladder cancer

AIM

Cancer-testis antigens (CTAs) have specific expression in gametogenic tissues and aberrant expression in cancers. Materials & methods: We assessed expression of five testis-specific genes namely KIF2B, CST8, TMEM225, RBM46, OAZ3 in bladder cancer tissues, adjacent non-neoplastic tissues and urinary cell pellets (UCPs) of bladder cancer patients compared with nonmalignant conditions.

RESULTS

Expressions of all CTAs were higher in UCPs of bladder cancer patients compared with nonmalignant conditions. RBM46 expression in UCPs was higher in patients with recurrent tumors compared with primary tumors and in patients without hematuria compared with those having hematuria. TMEM225 expression in tumoral tissues was higher in high-grade tumors compared with low-grade tumors.

CONCLUSION

Expression analysis of CTAs in UCP might provide diagnostic information about bladder cancer.

GPR62 constitutively activates cAMP signaling but is dispensable for male fertility in mice

G-protein-coupled receptors (GPCRs) participate in diverse physiological functions and are promising targets for drug discovery. However, there are still over 140 orphan GPCRs whose functions remain to be elucidated. Gpr62 is one of the orphan GPCRs that is expressed in the rat and human brain. In this study, we found that Gpr62 is also expressed in male germ cells in mice, and its expression increases along with sperm differentiation. GPR62 lacks the BBXXB and DRY motifs, which are conserved across many GPCRs, and it was able to induce cAMP signaling in the absence of a ligand. These structural and functional features are conserved among mammals, and the mutant analysis of GPR62 has revealed that lacking of these motifs is involved in the constitutive activity. We also found that GPR62 can homooligomerize, but it is not sufficient for its constitutive activity. We further investigated its physiological function by using Gpr62 knockout (Gpr62^-/-) mice. Gpr62^-/- mice were born normally and did not show any abnormality in growth and behavior. In addition, both male and female Gp62^-/- mice were fertile, and the differentiation and motility of spermatozoa were normal. We also found that Gpr61, the gene most similar to Gpr62 in the GPCR family shows a constitutive activity and an expression pattern similar to those of Gpr62 Our results suggest that GPR62 constitutively activates the cAMP pathway in male germ cells but is dispensable for male fertility, which is probably due to its functional redundancy with GPR61.

A critical role of solute carrier 22a14 in sperm motility and male fertility in mice

We previously identified solute carrier 22a14 (Slc22a14) as a spermatogenesis-associated transmembrane protein in mice. Although Slc22a14 is a member of the organic anion/cation transporter family, its expression profile and physiological role have not been elucidated. Here, we show that Slc22a14 is crucial for sperm motility and male fertility in mice. Slc22a14 is expressed specifically in male germ cells, and mice lacking the Slc22a14 gene show severe male infertility. Although the overall differentiation of sperm was normal, Slc22a14^-/- cauda epididymal spermatozoa showed reduced motility with abnormal flagellar bending. Further, the ability to migrate into the female reproductive tract and fertilise the oocyte were also impaired in Slc22a14^-/- spermatozoa. The abnormal flagellar bending was thought to be partly caused by osmotic cell swelling since osmotic challenge or membrane permeabilisation treatment alleviated the tail abnormality. In addition, we found structural abnormalities in Slc22a14^-/- sperm cells: the annulus, a ring-like structure at the mid-piece-principal piece junction, was disorganised, and expression and localisation of septin 4, an annulus component protein that is essential for the annulus formation, was also impaired. Taken together, our results demonstrated that Slc22a14 plays a pivotal role in normal flagellar structure, motility and fertility in mouse spermatozoa.