Abstract
Although, it is known that spermatozoa harbor a variety of RNAs that may influence embryonic development, little is understood about sperm transcriptomic differences in relation to fertility, especially in buffaloes. In the present study, we compared the differences in sperm functional attributes and transcriptomic profile between high- and low-fertile buffalo bulls. Sperm membrane and acrosomal integrity were lower (P < 0.05), while protamine deficiency and lipid peroxidation were higher (P < 0.05) in low- compared to high-fertile bulls. Transcriptomic analysis using mRNA microarray technology detected a total of 51,282 transcripts in buffalo spermatozoa, of which 4,050 transcripts were differentially expressed, and 709 transcripts were found to be significantly dysregulated (P < 0.05 and fold change >1) between high- and low-fertile bulls. Majority of the dysregulated transcripts were related to binding activity, transcription, translation, and metabolic processes with primary localization in the cell nucleus, nucleoplasm, and in cytosol. Pathways related to MAPK signaling, ribosome pathway, and oxidative phosphorylation were dysregulated in low-fertile bull spermatozoa. Using bioinformatics analysis, we observed that several genes related to sperm functional attributes were significantly downregulated in low-fertile bull spermatozoa. Validation of the results of microarray analysis was carried out using real-time qPCR expression analysis of selected genes (YBX1, ORAI3, and TFAP2C). The relative expression of these genes followed the same trend in both the techniques. Collectively, this is the first study to report the transcriptomic profile of buffalo spermatozoa and to demonstrate the dysregulation of functionally relevant transcripts in low-fertile bull spermatozoa. The results of the present study open up new avenues for understanding the etiology for poor fertility in buffalo bulls and to identify fertility biomarkers.
Highlights
Buffaloes contribute a major share to the world’s milk supply, and recent trends show that the volume of buffalo milk is increasing steadily at about 3% per year [1]
The proportion of spermatozoa with protamine deficiency was higher in low-fertile bulls compared to either highor medium-fertile bulls
We report here that sperm functional attributes were altered and transcripts involved in MAPK signaling, ribosome pathway, and oxidative phosphorylation were dysregulated in low-fertile bull spermatozoa
Summary
Buffaloes contribute a major share to the world’s milk supply, and recent trends show that the volume of buffalo milk is increasing steadily at about 3% per year [1]. The full production potential buffaloes, remain unexploited due to poor reproductive efficiency [2]. Poor conception rates with artificial insemination are considered as a prime reason for low reproductive efficiency in buffaloes [1, 3]. Several studies tried to identify the most important sperm phenotypic characteristics associated with sperm-fertilizing potential [4, 5]; discriminating low-fertile bulls from high-fertile bulls remains to continue as a challenge. Recent evidences indicate existence of specific differences in sperm functional attributes and sperm molecules such as mRNAs [7], proteins [8], and metabolites [9] between high- and low-fertile bulls
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