Aged men share the sperm protein PATE1 defect with young asthenozoospermia patients.

STUDY QUESTION

Does a defect in the human sperm-located protein prostate and testis expressed 1 (PATE1) exist in both aged men and young asthenozoospermia patients?

SUMMARY ANSWER

A defect in sperm PATE1 exists in both aged men and young asthenozoospermia patients, and an antibody against PATE1 can decrease human sperm motility and zona-free hamster oocyte penetration.

WHAT IS KNOWN ALREADY

Both aged men and young asthenozoospermia patients have poor sperm quality. The PATE1 protein seems to mediate sperm-egg interactions; however, the mechanisms are still unknown.

STUDY DESIGN, SIZE, DURATION: This was a case-control study including 60 young fathers (aged 28-32 years) and 60 aged fathers (68-72 years old) who donated semen by masturbation after 7 days of sexual abstinence. Comparative sperm proteome analysis from the young fathers and aged fathers was performed to discover key proteins. The target protein PATE1 was chosen and validated by western blotting and immunohistochemistry. Quantitative assessment of sperm PATE1 protein was performed on sperm from 60 young fathers, 60 aged fathers and 110 young asthenozoospermia patients. Furthermore, an antibody against PATE1 assay was used to test whether PATE1 participated in sperm motility and penetration of zona-free hamster egg.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Samples were pooled and separated by two-dimensional gel electrophoresis followed by identification by matrix-assisted laser desorption/ionization time of flight mass spectrometry. Western blotting and immunohistochemistry were used to validate the confidence of proteomic data. Sperm immunofluorescence quantification experiments disclosed whether the aged men indeed shared the same PATE1 defect with 110 young asthenozoospermia patients. The sperm motility test and penetration of zona-free hamster egg assay were performed for PATE1.

MAIN RESULTS AND THE ROLE OF CHANCE

Twenty-two sperm proteins with significant differential expression between young adults and aged men were identified (P < 0.05, mean ratio >1.5), including 13 proteins with decreased expressions with aging. Based on bioinformatics, PATE1 was chosen for further study, and exhibited similar changes in expression level and localization on sperm from aged men and young asthenozoospermia patients. Antibody blocking revealed that PATE1 was involved in sperm-egg penetration and sperm motility.

LIMITATIONS, REASONS FOR CAUTION: Before any clinical application of PATE1 as a biomarker for the diagnosis of male infertility, more cases should be used to evaluate confidence in this approach.

WIDER IMPLICATIONS OF THE FINDINGS

This study revealed a common molecular basis underlying the decline in sperm quality in the natural aging process and in young men with asthenozoospermia. The data should greatly contribute to the development of molecular evaluation of sperm quality, and the diagnosis and treatment of asthenozoospermia.

STUDY FUNDING/COMPETING INTERESTS: This work was supported by grants from the National Natural Science Foundation of China (NO. 81300533, 81370013 and 81000277) and Shandong Provincial Natural Science Foundation, China (ZR2013HQ002, ZR2014HQ068). The authors declare no competing financial interests.