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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #161194
Title: A LARGE-SAMPLE QTL STUDY IN MICE: III. REPRODUCTION

Author
item ROCHA, JOAO - UNIV. OF NEBR-LINCOLN
item EISEN, EUGENE - NORTH CAROLINA STATE
item SIEWERDT, FRANK - NORTH CAROLINA STATE
item Van Vleck, Lloyd
item POMP, DANIEL - UNIV. OF NEBR.-LINCOLN

Submitted to: Mammalian Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2004
Publication Date: 11/1/2004
Citation: Rocha, J.L., Eisen, E.J., Siewerdt, F., Van Vleck, L.D., Pomp, D. A large-sample qtl study in mice: III. Reproduction. 2004. Mammalian Genome 15:878-886.

Interpretive Summary: Reproductive efficiency is a major component of food production systems, and its improvement leads to economic benefits of large impact. Unfortunately, reproductive phenotypes normally have low heritabilities and are difficult to improve genetically. Identification of quantitative trait loci (QTL) with individual genetic effects would be relevant to development of DNA-assisted genetic improvement. Such studies targeting female reproductive traits have been scarce relative to studies for traits such as growth and body composition. Mice provide an experimental model to help understand the genetic basis of complex traits such as female reproductive traits. From an experiment to evaluate the genetic basis of complex reproductive traits using mice selected long-term for high and low growth, records of 439 females were analyzed to detect QTL for correlated female reproductive traits such as litter size, ovulation rate, and embryonic survival. The 15 QTL that were detected on 5 chromosomes can be categorized into two groups: 1) those with effects on number of live fetuses which were accompanied by effects on number of dead fetuses and 2) QTL free of such undesirable correlated effects. The QTL found for ovulation rate did not overlap with the QTL found for litter size, which probably indicates the importance of uterine capacity. Large dominance effects were identified for most QTL detected as well as over-dominance. These results may provide a guide to similar studies with litter bearing livestock such as pigs.

Technical Abstract: Using lines of mice having undergone long-term selection for high and low growth, a large-sample (n = ~ 1,000) F2 experiment was conducted to gain further understanding of the genetic architecture of complex polygenic traits such as reproduction. Composite interval mapping on data from 10 wk old F2 females (n = 439) detected 15 QTL on 5 chromosomes influencing reproduction measured at day 16 of gestation. The 15 QTL can be broadly categorized into two groups: those with effects on number of live fetuses (LF) which were accompanied by effects on number of dead fetuses (DF), and QTL free of such undesirable effects. The QTL for ovulation rate did not overlap with QTL for litter size, which probably indicates the importance of uterine capacity. Large dominance effects were identified for most significant QTL. Over-dominance was also found. The QTL with largest effects were detected in regions of chromosome 2, where large QTL effects for growth and fatness have also been found and where corroborating evidence from other studies exists. Considerable overlap between locations of QTL for reproductive traits and for growth traits agrees with positive correlations usually observed among these types of phenotypes. Some support for the importance of epistasis and QTL x environment interactions for reproduction was detected. Traits with low heritability require considerably larger sample sizes to achieve effective power of QTL detection. This is unfortunate as traits with low heritability are among those that could most benefit from QTL-complemented breeding and selection strategies in food animal production.