Background: Cattleyak are the Fl hybrids between (♀) yak (Bos grunniens) and (♂) cattle
(Bos taurus). Cattleyak exhibit higher capability in adaptability to a harsh environment and display
much higher performances in production than the yak and cattle. The cattleyak, however, are females
fertile but males sterile. All previous studies greatly focused on testes tissues to study the mechanism
of male infertility in cattleyak. However, so far, no transcriptomic study has been conducted on the epididymides
of yak and cattleyak.
Objective: Our objective was to perform comparative transcriptome analysis between the epididymides
of yak and cattleyak and predict the etiology of male infertility in cattleyak.
Methods: We performed comparative transcriptome profiles analysis by mRNA sequencing in the epididymides
of yak and cattleyak.
Results: In total 3008 differentially expressed genes (DEGs) were identified in cattleyak, out of which
1645 DEGs were up-regulated and 1363 DEGs were down-regulated. Thirteen DEGs were validated by
quantitative real-time PCR. DEGs included certain genes that were associated with spermatozoal maturation,
motility, male fertility, water and ion channels, and beta-defensins. LCN9, SPINT4, CES5A, CD52,
CST11, SERPINA1, CTSK, FABP4, CCR5, GRIA2, ENTPD3, LOC523530 and DEFB129, DEFB128,
DEFB127, DEFB126, DEFB124, DEFB122A, DEFB122, DEFB119 were all downregulated, whereas
NRIP1 and TMEM212 among top 30 DEGs were upregulated. Furthermore, protein processing in endoplasmic
reticulum pathway was ranked at top-listed three significantly enriched KEGG pathways that as
a consequence of abnormal expression of ER-associated genes in the entire ER protein processing pathway
might have been disrupted in male cattleyak which resulted in the downregulation of several important
genes. All the DEGs enriched in this pathway were downregulated except NEF.
Conclusion: Taken together, our findings revealed that there were marked differences in the epididymal
transcriptomic profiles of yak and cattleyak. The DEGs were involved in spermatozoal maturation,
motility, male fertility, water and ion channels, and beta-defensins. Abnormal expression of ERassociated
genes in the entire ER protein processing pathway may have disrupted protein processing
pathway in male cattleyak resulting in the downregulation of several important genes involved in
sperm maturation, motility and defense.