Mapping and investigation of candidate genes for reproduction and production traits in the pig
Date
1997
Authors
Vincent, Amy Louise
Major Professor
Advisor
Rothschild, Max F.
Committee Member
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Abstract
The purpose of these investigations was to identify candidate genes for economically important traits in pigs, map them using genetic and physical techniques, and identify relationships between these genes and related traits. By adding these genes to the genetic linkage and physical maps, they also become anchors for map comparisons between species, such as human and pig. The prolactin (PRL), prolactin receptor (PRLR), and leptin receptor (LEPR) genes were investigated as candidate genes because of their physiological functions. Prolactin is a hormone produced during gestation in the pig and is thought to maintain pregnancy through sustaining the production of progesterone. Prolactin is also essential after parturition, when it is believed to initiate transcription of milk protein genes in the mammary gland.
Both of these actions are mediated through the prolactin receptor, which has been shown to be expressed in various reproductive and endocrine tissues in several mammalian species. The leptin receptor gene was pursued since it is the specific receptor for the hormone leptin. Leptin is produced in fat tissue and is thought to regulate appetite and satiety. Several obese strains of rats and mice have been identified that possess lesions in the LEPR gene. Carcass quality, especially excessive fat levels, is an issue in which both meat packers and hog farmers are concerned. With the public demanding leaner and more uniform pork, genes associated with such traits will be of value.
The mapping efforts of this study were successful in placing these three loci on both the physical and linkage maps of the PiGMaP consortium. The PRL gene was linkage and physically mapped to pig chromosome 7, the PRLR gene was linkage and physically mapped to pig chromosome 16, and the LEPR gene was linkage mapped to pig chromosome 6. PRLR was shown to be significantly linked to litter size in three commercial lines of pigs from PIC, a swine breeding stock company. An analysis with phenotypic data from an ISU resource population and LEPR genotypes are suggestive of associations between this gene and growth and carcass traits.
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thesis