Mastrangelo, S. | Search bioRxiv

bioRxiv2024

Genomic analysis revealed hotspots of genetic adaptation and risk of disappearance in the Brazilian goat populations

We accessed a 50K Illumina SNP genotype dataset from two important goat breeds of the Brazilian semi- arid region to analyze the abundance and length of runs of homozygosity (ROH). This analysis aims to elucidate the importance of adaptation history in the genome of the Brazilian goat populations and to measure genomic inbreeding. Heterozygosity-rich regions (HRR) or genome regions of high genetic variability provide clues about how diversity might be associated with increased fitness, avoiding deleterious homozygous alleles. Overall, 22,872 ROH were identified. The average number of ROH per individual ranged from 74.73 (Anglo-Nubian commercial breed) to 173.85 (Marota landrace). Analysis of the distribution of runs of homozygosity according to their size showed that, for both breeds, the majority of ROH were in the short (<2.0 Mb) category (65.6%). ROH-based inbreeding (FROH) revealed low levels in Anglo-Nubian (0.0627) and high levels in Marota (0.1419), likely due to a reduction in effective population size over generations in the Marota landrace. We defined islands of ROH and HRR and identified common regions in the Marota goat, where genes related to various traits such as embryonic development, body growth, lipid homeostasis, and brain functions are located. These results indicate that such regions are associated with many traits and have therefore been under selective pressure in these goat breeds reared for different purposes.

genomics↗

bioRxiv2018

Novel and known signals of selection for fat deposition in domestic sheep breeds from Africa and Eurasia

Genomic regions subjected to selection frequently show signatures such as within-population reduced nucleotide diversity and outlier values of differentiation among differentially selected populations. In this study, we analyzed 50K SNP genotype data of 373 animals belonging to 23 sheep breeds of different geographic origins using the Rsb and FST statistical approaches, to identify loci associated with the fat-tail phenotype. We also checked if these putative selection signatures overlapped with regions of high-homozygosity (ROH). The analyses identified novel signals and confirmed the presence of selection signature in genomic regions that harbor candidate genes known to affect fat deposition. Several genomic regions that frequently appeared in ROH were also identified within each breed, but only two ROH islands overlapped with the putative selection signatures. The results reported herein provide the most complete genome-wide study of selection signatures for fat-tail in African and Eurasian sheep breeds; they also contribute insights into the genetic basis for the fat tail phenotype in sheep, and confirm the great complexity of the mechanisms that underlie quantitative traits, such as the fat-tail.

genetics↗