The role of PIT1 in the putative quantitative trait loci region on pig chromosome 13

PIT1 is an essential regulatory gene of growth hormone (GH), prolactin (PRL) and thyrotropin β subunit. Previously, PIT1 polymorphisms and the chromosomal region near PIT1 in multiple pig populations is significantly associated with fatness and growth quantitative trait loci (QTLs) on pig chromosome 13. The purpose of this study is to confirm these previous results and clarify the role of the PIT1 gene in the putative QTL region.; Cloning of the full length PIT1 cDNA was completed. The pig PIT1 cDNA and its deduced amino acids have approximately 90% and 95% sequence similarity respectively with the PIT1 cDNA and amino acids in other species. Several PIT1 alternative spliced forms were also identified. The Δ3PIT1, which is missing the entire exon 3, was unique to pig. Potentially different functions of the pig Δ3PIT1 from PIT1 were analyzed. The pig PIT1 protein could specifically bind to the rat GH and PRL promoter regions while the pig Δ3PIT1 protein could not. Possible protein-protein interactions between Δ3PIT1 and PIT1 were tested. Δ3PIT1 protein was shown to not affect PIT1DNA binding. The results of functional studies revealed that PIT1 could play an important role in pig growth as it does in other species.; Analyses of additional populations detected an association between PIT1 and birth weight, confirming the previous studies. Growth and carcass traits in the ISU F₂ families were analyzed and four microsatellite markers flanking the PIT1 gene were included. The data were analyzed using interval mapping and single marker methods. Significant evidence of a QTL for first rib backfat thickness was detected approximately 20 cM away from PIT1 by using interval mapping analyses, and linkage disequilibrium between PIT1 and the backfat QTL was shown in single marker analyses. Evidence of a QTL for birth weight was detected at the estimated PIT1 position in interval mapping analyses and verified by the single marker analyses. The results of QTL analyses confirmed the previous published QTL work on pig chromosome 13 for the birth weight QTL, but suggest that other genes in the region are responsible for the detected backfat thickness QTL.