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Sperm biomolecules impact the reproductive success of a bull in many ways from fertilization to the health of the offspring. The energy produced within the sperm enables them to remain motile and allows them to participate in fertilization events. In this study, we deciphered the genes associated with energy production and their influence on the fertility rate. Post-thaw buffalo semen samples (n=21) were analysed for sperm kinematics and field fertility for selecting high (n=5) and low (n=5) fertile samples. Sperm total RNAs were extracted using a double lysis method followed by column-based extraction and sequenced using the Illumina platform. The expression levels of the genes involved in energy-regulating pathways were analyzed. Among these genes, 14.6% were significantly (p<0.05) differentially expressed between high and low fertile sperm. The expression levels of up-regulated genes such as JAK3, DDX5, PRKCZ, CHD4, CHD5, and ADCY3 had a strong positive correlation (r>0.5) with progressive motility and velocities. The up-regulated genes were involved in chemokine signaling (ADCY2 and JAK2, p=0.0001), calcium signaling (AGTR1 and SLC25A4,p=0.0002) and oocyte meiosis (ADCY2 and ADCY3, p=0.049). The increase in the expression of ATP-producing genes substantiate the improved progressive motility (64.51±5.79 vs 33.07±3.34 %), curvilinear velocity (70.58±4.32 vs 50.15±4.92 μm/sec), straight-line velocity (39.84±3.16 vs 26.02±2.52 μm/sec) and average path velocity (49.46±3.59 vs 32.99±3.45 μm/sec) in high fertile bulls compared to low fertile bulls. The study suggests that the expression level of differentially expressed genes associated with energy-regulating pathways influences the fertilizing ability of sperm. [ABSTRACT FROM AUTHOR]

The objective of this study was to identify the sperm-expressed genes and their pathways in maintaining acrosomal integrity for elucidating the regulatory genes involved in determining bull fertility. Semen samples collected from Holstein-Friesian bulls (n=12) were analyzed for acrosomal integrity and were grouped into high acrosomal integrity (n=6) and low acrosomal integrity (n=6). In these sperm samples, total RNA was isolated and subjected to whole transcriptome profiling using Illumina platform. Bioinformatic analyses led to the identification of 1601 up-regulated (TMCO2, GTSF1, SWI5, CCDC174 and CABS1) and 567 down-regulated (MYCB, RPS21 and PPIA) genes. The study also validated the expression levels of CCDC174 and TMCO2 using real-time PCR. The pathways [log2 (p-value)] such as spermatid development (12.17), protein transport (9.57) and mitochondrial electron transport (10.20) were enriched in the up-regulated genes. These identified pathways and their associated transcripts in high acrosome integrity group suggest that these pathways are essential for maintaining acrosome integrity and sperm fertility in bulls. [ABSTRACT FROM AUTHOR]

Bulls with acceptable semen quality vary in actual field fertility and this can be elucidated by studying the expression levels of mRNAs in the sperm. The present study aimed at assessing the variations in the sperm gene expression levels of PRM1, CCDC174, RPL36A, TMCO2, SWI5 and OIT3 in bulls differing in fertility status. Frozen semen samples from Holstein-Friesian bulls were classified into high-fertile (n = 8, average field conception rate = 46.1 ± 0.51, p < 0.001) and sub-fertile (n = 7, average field conception rate = 39.4 ± 0.69) groups. In the post-thaw semen samples, sperm kinematics, structural and functional membrane integrities, mitochondrial membrane potential and chromatin distribution were analyzed. The sperm total RNA was subjected to gene expression studies by Real-Time PCR. Multivariate regression analysis was performed using gene expression levels and conception rates. The sperm functional attributes did not differ significantly between the groups. The relative mRNA levels (fold change) of CCDC174 (6.20), RPL36A (4.66), SWI5 (1.86) and OIT3 (1.53) were higher in high-fertile bulls. Further, the expression level of the CCDC174 gene was significantly (p = 0.02) up-regulated in high-fertile bulls. The fertility prediction multivariate model with genes, CCDC174, RPL36A, TMCO2 and OIT3 had the maximum coefficient of determination (R2 = 0.68) with the field conception rate. This model had 93.3% bull fertility prediction accuracy with 100% sensitivity and 87.5% specificity. The study suggests that the expression level of CCDC174 can be used as a potential marker for assessing bull fertility. [ABSTRACT FROM AUTHOR]