KIRREL is differentially expressed in adipose tissue from 'fertil+' and 'fertil-' cows: in vitro role in ovary?

Genome-wide discovery of underlying genetic factors associated with fresh and frozen-thawed semen traits in composite ram breeds exhibiting different cryotolerance

Fewer studies investigate the effects of underlying genetic factors related to semen characteristics, significantly affecting sheep farm profitability. This study aimed to identify single nucleotide polymorphisms (SNP) and genomic regions associated with fresh and frozen-thawed semen traits in rams with low (Hasak) and high (Hasmer) cryotolerance. Semen collected from 11 (5 Hasak with low and 6 Hasmer with high cryotolerance) rams cryopreserved in 0.25 ml straws in the breeding season. Quality characteristics were determined in fresh, equilibrated, and frozen-thawed semen. A Genome-Wide Association Study (GWAS) was conducted to unveil the genetic structure that might be attributed to cryotolerance in low and high cryotoleranced rams. Fresh (regarding total and progressive motility) and equilibrated semen quality were similar in Hasak and Hasmer rams (p > 0.6). However, the freeze-thawing process had a more pronounced negative effect on ram semen traits in Hasak than in Hasmer (p < 0.05). GWAS revealed 27 SNPs correlated with post-thaw semen parameters. Moreover, network analyses revealed pathways related to sperm ion channels and their activities, providing insights into the intricate molecular mechanisms underlying sperm physiology and emphasizing their role in potentially impacting sperm cryotolerance. The functional significance of detected SNPs and the associated pathways require further exploration.

Genome-Wide Association Studies in Indian Buffalo Revealed Genomic Regions for Lactation and Fertility

Murrah breed of buffalo is an excellent dairy germplasm known for its superior milk quality in terms of milk fat and solids-not-fat (SNF); however, it is often reported that Indian buffaloes had lower lactation and fertility potential compared to the non-native cattle of the country. Recent techniques, particularly the genome-wide association studies (GWAS), to identify genomic variations associated with lactation and fertility traits offer prospects for systematic improvement of buffalo. DNA samples were sequenced using the double-digestion restriction-associated DNA (RAD) tag genotyping-by-sequencing. The bioinformatics pipeline was standardized to call the variants, and single-nucleotide polymorphisms (SNPs) qualifying the stringent quality check measures were retained for GWAS. Over 38,000 SNPs were used to perform GWAS on the first two principal components of test-day records of milk yields, fat percentages, and SNF percentages, separately. GWAS was also performed on 305 days’ milk yield; lactation persistency was estimated through the rate of decline after attaining the peak yield method, along with three other standard methods; and breeding efficiency, post-partum breeding interval, and age at sexual maturity were considered fertility traits. Significant association of SNPs was observed for the first principal component, explaining the maximum proportion of variation in milk yield. Furthermore, some potential genomic regions were identified to have a potential role in regulating milk yield and fertility in Murrah. Identification of such genomic regions shall help in carrying out an early selection of high-yielding persistent Murrah buffaloes and, in the long run, would be helpful in shaping their future genetic improvement programs.

Genome-wide association study to identify genomic regions and positional candidate genes associated with male fertility in beef cattle

Fertility plays a key role in the success of calf production, but there is evidence that reproductive efficiency in beef cattle has decreased during the past half-century worldwide. Therefore, identifying animals with superior fertility could significantly impact cow-calf production efficiency. The objective of this research was to identify candidate regions affecting bull fertility in beef cattle and positional candidate genes annotated within these regions. A GWAS using a weighted single-step genomic BLUP approach was performed on 265 crossbred beef bulls to identify markers associated with scrotal circumference (SC) and sperm motility (SM). Eight windows containing 32 positional candidate genes and five windows containing 28 positional candidate genes explained more than 1% of the genetic variance for SC and SM, respectively. These windows were selected to perform gene annotation, QTL enrichment, and functional analyses. Functional candidate gene prioritization analysis revealed 14 prioritized candidate genes for SC of which MAP3K1 and VIP were previously found to play roles in male fertility. A different set of 14 prioritized genes were identified for SM and five were previously identified as regulators of male fertility (SOD2, TCP1, PACRG, SPEF2, PRLR). Significant enrichment results were identified for fertility and body conformation QTLs within the candidate windows. Gene ontology enrichment analysis including biological processes, molecular functions, and cellular components revealed significant GO terms associated with male fertility. The identification of these regions contributes to a better understanding of fertility associated traits and facilitates the discovery of positional candidate genes for future investigation of causal mutations and their implications.