Protein tyrosine phosphatase non-receptor type 14 is a novel sperm-motility biomarker

Purpose To understand the molecular basis of sperm-motility and to identify related novel motility biomarkers. Methods Two-dimensional electrophoresis (2DE) followed by Reverse-phase-nano-high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (RP-nano-HPLC-ESI-MS/MS) were applied to establish the human sperm proteome. Then the sperm proteome of moderate-motile human sperm fraction and that of good-motile human sperm fraction from pooled spermatozoa of forty normozoospermic donors (Group 1 subjects) were compared to identify the dysregulated proteins. Among these down-regulated proteins, Protein tyrosine phosphatase non-receptor type 14 (PTPN14) was chosen to reconfirm by Western blotting and semi-quantitative reverse transcription polymerase chain reaction. For clinical application, Western blotting and real-time reverse transcription polymerase chain reaction was performed to compare the expression level of PTPN14 in (Group 2 subjects) nine normozoospermic controls and thirty-three asthenozoospermic patients (including 21 mild asthenozoospermic cases and 12 severe cases). Finally, bioinformatic tools prediction and immunofluorescence assay were performed to elucidate the potential localization of PTPN14. Results The expression levels of three proteins were observed to be lower in the moderate-motile sperm fraction than in good-motile sperm of group 1 subjects. Among three proteins with persistent down-regulation in the moderate-motile sperm, we reconfirmed that the expression level of PTPN14 was significantly lower in both mRNA and protein levels from the moderate-motile sperm fraction. Further, down-regulation of PTPN14 was found at the translational and transcriptional level in the asthenozoospermic men. Finally, Bioinformatic tools prediction and immunofluorescence assay showed that PTPN14 maybe predominantly localized at the mitochondria in the midpiece of human ejaculated sperm. Conclusions Proteomics tools were applied to identify three possible sperm motility-related proteins. Among these proteins, PTPN14 was highly likely a novel sperm-motility biomarker and a potential mitochondrial protein.