Comprehensive proteomics analysis of bovine sperm head plasma membrane associated with fertility

Bull fertility impacts herd fertility, but accurately predicting male fertility from sperm characteristics is difficult once extremes are removed. The objectives of this study were identification, relative quantification, and comparison of sperm head plasma membrane (HPM) proteomics in bulls of differing bull fertility index (BFI). HPM from one fresh ejaculate from 16 Holstein bulls (8 each high and low fertility) was extracted, digested and assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The MS spectra were aligned to UniProtKB mammals, identified, and characterized by Spectrum Mill. Mass Profiler Professional statistical analysis of the 22,117 total proteins identified in all bulls, after database search, revealed 67 proteins [unique plus homologous, 1% false discovery rate] whose abundance differed at least 2-fold (differentially abundant proteins, DAPs) between the 3 bulls each with highest and lowest BFI [high fertility (HF) BFI 105.66 ± 0.54 > low fertility (LF) BFI 91.33 ± 1.44; p < 0.01]. Gene ontology assigned the 48 DAPS increased in HF to sperm-specific function and fertility-related mechanisms, and the 19 HF-decreased DAPs primarily to catalytic and transporter activity. Meta analysis and linear regression each confirmed that the BFI of the 6 HF/LF bulls significantly correlated to the DAPS (regression r2 = 0.65 to 0.97, p ≤ 0.05), but importantly in the 16-bull population, linear regression found that 38 of the HF-increased DAPS positively correlated to BFI (r2 = 0.29 to 0.66; p ≤ 0.05), and 4 of the HF-decreased DAPS negatively correlated (r2 = 0.26 to 0.44; p ≤ 0.05). In summary, this study identified HPM proteins with important roles in sperm fertilization and significant correlations with bull fertility.