The Role Of PRSS37, Prss54 Gene In The Male Reproduction And The Potential Clinical Value Of PRSS37 In Unexplained Male Infertility

PRSS54?inactive protease serine 54?,also known as CT67?cancer/testis antigen 67?or KLKBL4?kallikrein-like protein 4?,is a previously uncharacterized gene,belongs to the peptidase S1 family and plasma kallikrein subfamily,PRSS54 contains one peptidase S1 domain.Tissue expression pattern analysis showed that Prss54 is highly and restrictively expressed in the testis tissue of adult male mice and human being.Further analysis revealed that during the first spermatogenesis wave the mRNA transcription of Prss54 was started on Postnatal Day 23.In human testicular round spermatid Sb1 started to appear PRSS54protein,PRSS54 located in sperm acrosome region in the mouse and human being,overlapping with PNA fluorescence signal.Mice deficient for Prss54 showed male subfertility,but their testicular development,spermatogenesis,sperm count and motility,mating behavior remained unaffected.In vivo fertilization assay revealed that Prss54^-/-mice exhibit a markedly decreased fertilization rate?18%vs.85%of that in control mice?.In vitro fertilization study further showed Prss54^-/-sperm cannot penetrate effectively through the zona pellucid when exposed to zona-intact eggs.Acrosome in Prss54^-/-sperm could not cover the nuleus and only bind to the side of the nucleus.During spermiogenesis,electron dense acrosomal granule did not lie in the middle site of the acroplaxome,and did not bind tightly to acroplaxome.Migration ability from the uterus into the fallopian tube was also impaired.Targeted deletion of the Prss54gene in mice resulted in male subfertility due to abnormal sperm heads characterized by ectopic acrosome location in sperm head.Since the occurrence of deformed spermatozoa is one of the common abnormalities leading to malfunction sperm,identification of Prss54 might provide insight into the molecular cue underlying causes of male infertility in human being.Our previous study showed that PRSS37,a putative trypsin-like serine protease,is required for male fertility in mice.PRSS37-deficient mice exhibited male infertility but their spermatogenesis,sperm morphology,motility and mating activity remained unaffected.As in the mouse,PRSS37 is expressed exclusively in the testis in the male reproductive organs of humans.PRSS37 protein is highly conserved in mammals during evolution,implying that it may play a key role in male reproductive success in mammals during evolution.However,at present no information is available regarding whether PRSS37 is critical for human fertilization or regarding its clinical relevance in infertility.In the present study,we identified PRSS37 protein expression in the adult human testis,particularly in the elongating spermatid and the elongated spermatid during spermiogenesis.PRSS37 also existed in the ejaculated sperm,primarily in the acrosome region,but was no longer present after the acrosome reaction induced by A23187 in human tubal fluid?HTF?medium including10%serum substitute supplement?SSS?in5%CO₂ at 37oC.PRSS37 in the sperm was associated with male fertility,dramatically lower in men with unexplained infertility compared with men with proven fertility or sperm donors.Our study showed that low expression levels of PRSS37 in the sperm might impair male fertility through abnormal activation of the proacrosin/acrosin system and premature proteolysis of ADAM2 prior to sperm capacitation in the female reproduction tract.Our result suggested that PRSS37,as a molecular biomarker,might improve the diagnosis and management of unexplained infertility,but more clinical trials would be required to test the hypothesis.