Genome-wide association study (GWAS) and functional genomics of parasite resistance in Morada Nova sheep

Abstract

Morada Nova is an indigenous Brazilian hair sheep breed well adapted to tropical climate regions. Among its economically important traits are good reproductive performance and high nematode gastrointestinal resistance. In the worldwide scenario of multiple anthelmintic resistance, parasite resistance is a very interesting trait for animal selection to avoid productive and economic losses. Among parasites of sheep, Haemonchus contortus, the barber pole worm, a blood-sucking parasite of abomasum, is the most prevalent and pathogenic nematode, leading to health problems, productive losses, anemia and death. Thus, selecting sheep resistant to nematodes is a very advantageous goal in animal breeding programs. Considering the quantitative nature of the trait, genomic approaches, mainly genome-wide association studies (GWAS), are more suitable to understand the genetic architecture of parasite resistance in comparison to candidate gene approaches. In this way, 287 Morada Nova lambs submitted to two consecutive artificial infections with H. contortus were assessed for egg per gram (EPG) counts, packed cell volume (PCV) and weight gain. After ranking and classification of animals with extreme phenotypes, 48 animals were genotyped with the Illumina OvineSNP50v3 chip, and abomasal tissues from 10 extreme phenotype lambs were submitted to RNA-seq. The objective of the present proposal is to perform GWAS and integrate genomic to transcriptomic data to identify molecular markers and functional changes associated with H. contortus resistance in sheep. This information can be used go guide animal selection, to control of gastrointestinal nematodes in flocks and to elucidate biological molecular mechanisms leading to parasite resistance in sheep. (AU)