Using a genomics approach to unravel candidate genes associated with heartwater disease resistance in South African indigenous goats.
Nuse, X.*1,2, Van Der Nest, M. A.3, Dzomba, E. F.1, Steyn, H. C.4, Muchadeyi, F. C.2
1 Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, South Africa.
2 Agricultural Research Council - Biotechnology Platform, Onderstepoort, Pretoria, South Africa.
3 Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa.
4 Department of Molecular Biology, Agricultural Research Council - OVI, Onderstepoort 0110, South Africa
Infectious diseases such as heartwater pose a significant challenge to ruminant production in Southern African countries. This tick-borne disease poses an economic threat to goat production in endemic regions infested by Amblyomma hebraeum ticks, the vector for the causative agent Ehrlichia ruminantium. The aim of this study was to employ a genome-wide association study (GWAS) approach to identify genomic regions and candidate genes associated with susceptibility/resistance to heartwater disease in South African indigenous goats from endemic and non-endemic regions. Blood and ear-tissue samples were collected from various goat breeds (Boer, Kalahari Red, Savanna, and village ecotypes) in heartwater endemic and non-endemic regions of SA. Genotyping was done using Illumina Goat65K SNP BeadChip array. Immunity against the disease across goat populations was tested using indirect fluorescent assay (IFA) test for antibody titre levels. The available phenotype of interest was made a binary character, cases (40-80 titre = 1) and controls (0 titre = 0) were used to perform association test (GWAS analysis). The first two principal components (PCs) separated goat populations into distinct clusters based on genetic variations. Multi-locus Mixed Model Analyses identified SNPs significantly associated with susceptibility/ resistance (FDR, p < 0.05). This included genomic regions and/or candidate genes on chromosomes 1 (PHLDB2), 4 (DGKI), 7 (BRD8), 8 (NTRK2, hnRNPK), 17 (PIWIL3, SGSM1, WSCD2) and 17 (gab1, FREM3, HHIP,/i>) harbouring genes that may influence the outcome of disease symptoms associated with heartwater. Results of this study therefore provide insights into genes and pathways linked to heartwater susceptibility or resistance in indigenous goats. This research has the potential to facilitate marker-assisted selection in goats, ultimately contributing to improved heartwater resistance in these valuable livestock.
Keywords: goats, GWAS, candidate genes, heartwater resistance
