Association of single-nucleotide polymorphisms in <i>NAT9 </i>and <i>MAP3K3</i> genes with litter size traits in Berkshire pigs

Abstract

Litter size is an economically important trait in the pig industry. We aimed to identify genetic markers associated with litter size, which can be used in breeding programs for improving reproductive traits. Single-nucleotide polymorphisms (SNPs) of Berkshire pigs in the <i>N-acetyltransferase 9</i> (<i>NAT9</i>) and <i>Mitogen-activated protein kinase kinase kinase 3 (MAP3K3)</i> genes were from RNA sequencing results, and already exist in the databank (NCBI), and were confirmed by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). A total of 272 Berkshire sows were used to examine the genotype, and their association with litter size traits was analyzed. The <i>NAT9</i> SNP was located in chromosome 12 exon 640 mRNA (A <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>></mml:mi></mml:math> G) and the <i>MAP3K3</i> SNP was located in chromosome 12 intron 11 (80, C <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>></mml:mi></mml:math> T). Association analysis indicated that the GG genotype of <i>NAT9</i> and the CT genotype of <i>MAP3K3</i> had the highest values for litter size traits. The GG genotype expressed higher levels of <i>NAT9</i> mRNA in the endometrium than the other genotypes did, and a positive correlation was found between litter size traits and <i>NAT9</i>, but not <i>MAP3K3</i> expression level. These results indicate that the <i>NAT9</i> and <i>MAP3K3</i> can be used as candidate genes applicable in breeding program for the improvement of litter size traits in Berkshire pigs.