Genome-wide association study reveals novel candidate genes for litter size in Markhoz goats

IntroductionThe Markhoz goat is the only breed that can produce high-quality fiber called mohair in Iran; however, the size of its population has faced a dramatic decline during the last decades, mainly due to the reluctance of farmers to rear Markhoz goats caused by a reduction in goat production income. Litter size at birth (LSB) and weaning (LSW) are two economically important reproductive traits for local goat breeders and have the potential of increasing the population growth rate. The present study was aimed to identify possible genomic regions that are associated with LSB and LSW in Markhoz goats using a genome-wide association study (GWAS). MethodsTo this end, 136 Markhoz goats with record(s) of kidding were selected for GWAS using the Illumina Caprine 50K bead chip. The individual breeding values (BV) of available LSB and LSW records estimated under an animal mixed model were used as the dependent variable in the GWAS, thereby incorporating repeated categorical variables of litter size. ResultsFour SNPs on chromosomes 2, 20 and 21 were identified to be significantly associated (FDR p < 0.05) with LSB after multiple testing correction under a Bayesian-information and Linkage-disequilibrium Iteratively Nested Keyway (BLINK) model. Least-square analysis was performed to investigate the effects of detected genotypes on LSB. Ultimately, the GWAS results introduced six candidate genes, including GABRA5, AKAP13, SV2B, PPP1R1C, SSFA2 and TRNAS-GCU in a 100 kb adjacent region of the identified SNPs. Previous studies proposed functional roles of GABRA5 and AKAP13 genes in reproductive processes; however, the role of other candidate genes in reproduction is not clear. ConclusionThese findings warrant further investigation for use in marker-assisted selection programs in Markhoz goats.

Automated summary

The Markhoz goat, a breed known for its high-quality mohair, has experienced a significant decline in population size in Iran due to decreased income from goat production. This study aimed to identify genomic regions associated with litter size at birth (LSB) and weaning (LSW) in Markhoz goats using a genome-wide association study (GWAS). The results identified several SNPs on chromosomes 2, 20, and 21 that were significantly associated with LSB, and six candidate genes in the identified region were also identified.