Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2006
Publication Date: 7/1/2006
Citation: Kim, J.G., Nonneman, D.J., Vallet, J.L., Wise, T.H., Rohrer, G.A. Sequence variation and evaluation of inhibin alpha-subunit and steroidogenic acute regulatory protein for reproductive traits in swine. Animal Genetics. 37:424-425. 2006. Interpretive Summary: Detection and identification of genes affecting litter size in swine is important because it can increase the quantity of lean pork through marker assisted selection and can expand our knowledge of the genetic basis of reproductive efficiency. The inhibin alpha-subunit (INHA) and steroidogenic acute regulatory protein (STAR) genes map to a chromosomal region in pigs that affects ovulation rate and are involved in the physiology of ovulation. The purpose of this study was to sequence the pig INHA and STAR genes, identify sequence variation within the gene and determine if they are associated with reproductive traits in advanced generations of the Meishan/White Composite resource population used for QTL detection. The analysis showed that they were not associated with ovulation rate or age at puberty. It appears that in subsequent generations since the QTL was identified, these markers are no longer linked with the causative gene responsible for the QTL effects on chromosome 15 which probably resides some distance away from INHA and STAR.
Technical Abstract: Quantitative trait loci (QTL) for ovulation rate have been identified in the pig and one region on chromosome 15 was reported in a Meishan cross and in lines selected for components of litter size. Porcine inhibin alpha-subunit (INHA) and steroidogenic acute regulatory protein (STAR) genes map to this region. INHA is a gonadal glycoprotein that heterodimerizes to form inhibins and regulates the secretion of pituitary follicle stimulating hormone (FSH). Plasma inhibin is correlated with higher ovulation rate in pigs. The transportation of cholesterol from the outer to the inner mitochondrial membrane is the rate limiting step for steroidogenesis and is conducted by STAR in testis, ovary and adrenal and is regulated by FSH and IGF1. The INHA and STAR genes were sequenced and evaluated as positional candidates for this QTL. Polymorphisms in the INHA and STAR gene were not associated with ovulation rate in advanced generations of the Meishan/White Composite resource population used for QTL detection. Linkage disequilibrium between these genomic locations and the causative variation has been disrupted in this population, and the gene responsible for the QTL effects on chromosome 15 probably resides some distance away from INHA and STAR.