Identification of quantitative trait loci affecting corpora lutea and number of teats in a Meishan × Duroc F2 resource population

Abstract

Understanding of the genetic control of female reproductive performance in pigs would offer the opportunity to utilize natural variation and improve selective breeding programs through marker-assisted selection. The Chinese Meishan is one of the most prolific pig breeds known, farrowing 3 to 5 more viable piglets per litter than Western breeds. This difference in prolificacy is attributed to the Meishan's superior prenatal survival. Our study utilized a 3-generation resource population, in which the founder grandparental animals were purebred Meishan and Duroc pigs, in a genome scan for QTL. Grandparent, F1, and F2 animals were genotyped for 180 microsatellite markers. Reproductive traits, including number of corpora lutea (number of animals = 234), number of fetuses per animal (n = 226), number of teats (n = 801), and total number born (n = 288), were recorded for F2 females. Genome-wide significance level thresholds of 1, 5, and 10% were calculated using a permutation approach. We identified 9 QTL for 3 traits at a 10% genome-wise significance level. Parametric interval mapping analysis indicated evidence of a 1% genome-wise significant QTL for corpora lutea on SSC 3. Nonparametric interval mapping for number of teats found 4 significant QTL on chromosomes SSC3 (P < 0.01), SSC7 (P < 0.01), SSC8 (P < 0.01), and SSC12 (P < 0.05). Partial imprinting of a QTL affecting teat number (P < 0.10) was detected on SSC8. Using the likelihood-ratio test for a categorical trait, 2 QTL for pin nipples were detected on SSC2 and SSC16 (P < 0.01). Fine mapping of the QTL regions will be required for their application to introgression programs and gene cloning.

High-resolution association mapping of number of teats in pigs reveals regions controlling vertebral development

“…Although many studies have found a QTL for NTE on SSC12 [9, 11, 12, 17, 18], only Guo et al [12] found a large QTL interval similar to ours in an F2 cross between Large White and Chinese Meishan. Within this region, we find the δ- EF1 gene is of particular interest because its expression in the somites [58] may suggest a role in vertebrae and mammary development in a mechanism similar to Vertnin , as described above.…”

“…The QTL which explains the most genetic variation is located on SSC7 and has been identified in other studies [9, 11, 12, 17, 18]. While Mikawa et al [48] reported an additive effect of this QTL on number of vertebrae, we observed a dominant or even overdominant effect on the number of teats in our population.…”

Molecular cloning, mRNA expression and imprinting status of PEG3, NAP1L5 and PPP1R9A genes in pig

“…In mammals in particular, imprinted genes have an important effect in the regulation of fetal growth, development, function of the placenta, and postnatal behavior (Isles and Holland, 2005). In pigs, many imprinted quantitative trait locus (QTL) significantly affect growth, backfat thickness, carcass composition and reproduction (de Koning et al, 2000;Sato et al, 2006;Ding et al, 2009;Uemoto et al, 2009;Ruckert and Bennewitz, 2010). The IGF2 gene, which was identified as the first imprinted gene in pigs, has important effects on porcine growth, meat quality and carcass composition, especially on fat deposition (Estellé et al, 2005).…”

Evidence for association of lymphoid enhancer-binding factor-1 <i>(LEF1)</i> with the number of functional and inverted teats in pigs

“…Quantitative trait loci (QTL) for teat traits on chromosome 8 have been identified by several authors (Cassady et al, 2001;Beeckmann et al, 2003;Sato et al, 2006). LEF1 was displayed in close proximity to these QTL and thus is a positional candidate gene.…”