Quantitative trait loci for body size components in mice

Abstract

Do body size components, such as weights of internal organs and long bone lengths, with different functions and different developmental histories also have different genetic architectures and pleiotropic patterns? We examine murine quantitative trait loci (QTL) for necropsy weight, four long bone lengths, and four organ weights in the LG/J x SM/J intercross. Differences between trait categories were found in number of QTL, dominance, and pleiotropic patterns. Ninety-seven QTLs for individual traits were identified: 52 for long bone lengths, 30 for organ weights, and 15 for necropsy weight. Results for long bones are typically more highly significant than for organs. Organ weights were more frequently over- or underdominant than long bone lengths or necropsy weight. The single-trait QTLs map to 35 pleiotropic loci. Long bones are much more frequently affected in groups while organs tend to be affected singly or in pairs. Organs and long bones are found at the same locus in only 11 cases, 8 of which also include necropsy weight. Our results suggest mainly separate genetic modules for organ weights and long bone lengths, with a few loci that affect overall body size. Antagonistic pleiotropy, in which a locus has opposite effects on different characteristics, is uncommon.

Genomic imprinting effects on adult body composition in mice

“…values for these same traits mapped in the F 2 population also are typically within this range, but differences between homozygotes often are Ͼ0.40 SD units (27,28). Thus, imprinting effects are similar in magnitude to dominance effects but small when compared with additive genotypic values.…”

“…Additive genotypic effects are clearly more common than imprinting effects in this population whereas imprinting and dominance effects are comparable in frequency. Like most aQTL and dQTL (28), the majority of iQTL affected several body composition traits, indicating the generally body-wide scope of imprinting effects.…”

“…The highest number of iQTL affecting any single trait was six (a number shared by liver, kidney, and body weight), which can be compared with the number (N) of significant additive (aQTL) and/or dominance (dQTL) QTL effects (genotypic values) found in the F 2 population for these same body composition traits (27,28). Overall, many more aQTL effects (n ϭ 51) than iQTL effects (n ϭ 29) were found for body composition.…”

Pleiotropic Patterns of Quantitative Trait Loci for 70 Murine Skeletal Traits

“…These regions lacked any detectable SNP variation between LG/J and SM/J despite being scored for .30 SNPs known to be polymorphic between inbred mouse strains (Hrbek et al 2006). In previously published work in this experimental population, for which only microsatellite genotypes were available, the average intermarker distance was 23 cM Kenney-Hunt et al 2006).…”

“…Among components of body size, there are now many published articles on the genetic architecture of skeletal traits and aspects of skeletal morphology using quantitative trait locus (QTL) analysis (Cheverud et al 1997Leamy et al 1999;Klein et al 2001;Klingenberg et al 2001;Chase et al 2002;Li et al 2002;Shimizu et al 2002;Christians et al 2003;Volkman et al 2003;Bouxsein et al 2004;Huang et al 2004;Alam et al 2005;Carrier et al 2005;Lang et al 2005;Ishimori et al 2006;Kenney-Hunt et al 2006;Wolf et al 2006;Christians and Senger 2007;Farber and Medrano 2007;Yu et al 2007;Zhou et al 2007). These studies are usually limited to a single trait or a few traits of interest, such as bone mineral density, or to a specific region of the skeleton, such as the innominate or mandible.…”