👤 Rostam Abdollahi-Arpanahi

Genome-wide scan for run of homozygosity (ROH) stretches, effective population size (Ne) and selection signatures can help to elucidate mechanisms of selection and pinpoint genomic regions linked with phenotypic traits. This study aimed to identify the genomic patterns of ROH, Ne and selection signatures in two Iranian main sheep breeds including Afshari and Qezel (known as meat and dairy sheep, respectively) using 49,017 single nucleotide polymorphisms (SNPs) generated using the ovine 50K SNP BeadChips. Analysis of ROH in Iranian sheep breeds revealed the differences in the pattern of ROH length and burden in these breeds. Inbreeding estimated based on ROH stretches showed very low amount of inbreeding in these indigenous sheep breeds. The Qezel breed displayed a higher Ne than Afshari breed. Furthermore, the potential selection was detected in genomic regions using three complementary approaches including FST (fixation index), XP-EHH (cross-population extended haplotype homozygosity), and hapFLK (haplotype differentiation). Our results identified the genomic regions that were enriched with the genes associated with immune response (e.g., IL23A, STAT2 and DOCK5), milk traits (e.g., PCCA, ACAP3, TTK and BTG3), energy metabolisms (e.g., GLS2), reproduction (e.g., ANGPT2), fecundity (e.g., BMP5), nervous system (e.g., DLG2, PCDH9, and FRMPD4), growth traits and muscle formation (NPY, MYF5 and PPP1R12A), and sweat gland development (SCNN1D). Some regions were also detected for the first time and overlapped with no genes suggesting novel loci associated with traits that differentiate these breeds. Overall, the finding of this study may shed light on the genomic regions linked to economically important traits in sheep as well as for developing the conservation and selection breeding programs. Show less

Heat stress negatively impacts the reproductive performance of dairy cows. The main objective of this study was to dissect the genetic basis underlying dairy cow fertility under heat stress conditions. Our first goal was to estimate genetic components of cow conception across lactations considering heat stress. Our second goal was to reveal individual genes and functional gene-sets that explain a cow's ability to conceive under thermal stress. Data consisted of 74 221 insemination records on 13 704 Holstein cows. Multitrait linear repeatability test-day models with random regressions on a function of temperature-humidity index values were used for the analyses. Heritability estimates for cow conception under heat stress were around 2-3%, whereas genetic correlations between general and thermotolerance additive genetic effects were negative and ranged between -0.35 and -0.82, indicating an unfavorable relationship between cows' ability to conceive under thermo-neutral vs. thermo-stress conditions. Whole-genome scans identified at least six genomic regions on BTA1, BTA10, BTA11, BTA17, BTA21 and BTA23 associated with conception under thermal stress. These regions harbor candidate genes such as BRWD1, EXD2, ADAM20, EPAS1, TAOK3, and NOS1, which are directly implicated in reproductive functions and cellular response to heat stress. The gene-set enrichment analysis revealed functional terms related to fertilization, developmental biology, heat shock proteins and oxidative stress, among others. Overall, our findings contribute to a better understanding of the genetics underlying the reproductive performance of dairy cattle under heat stress conditions and point out novel genomic strategies for improving thermotolerance and fertility via marker-assisted breeding. Show less