Genetic variation in body weight gain and composition in the intercross of Large (LG/J) and Small (SM/J) inbred strains of mice

Abstract

Strain intercross experiments provide a powerful means for mapping genes affecting complex quantitative traits. We report on the genetic variability of the intercross of the Large (LG/J) and Small (SM/J) inbred mouse strains as a guide to gene mapping studies. Ten SM/J males were crossed to 10 LG/J females, after which animals were randomly mated to produce F1, F2, and F3 intercross generations. The 1632 F3 animals from 200 full-sib families were used to estimate heritabilities and genetic correlations of the traits measured. A subset of families was cross-fostered at birth to allow measurement of the importance of post-natal maternal effects. Data was collected on weekly body weight from one to 10 weeks and on organ weights, body weight, reproductive fat pad weight, and tail length at necropsy in the intercross generations. There was no heterosis for age-specific weights or necropsy traits, except that one-week weight was the highest in the F2 generation, indicating heterosis for maternal effect in the F1 mothers. We found moderate to high heritability for most age-specific weights and necropsy traits. Maternal effects were significant for age-specific weights from one to four weeks but disappeared completely at ten-week weight. Maternal effects for necropsy traits were low and not statistically significant. Age-specific weights showed a typical correlation pattern, with correlation declining as the difference in ages increased. Among necropsy traits, reproductive fat pad and body weights were very highly genetically correlated. Most other genetic correlations were low to moderate. The intercross between SM/J and LG/J inbred mouse strains provides a valuable resource for mapping quantitative trait loci for body size, composition, and morphology<br>Os experimentos de intercruzamento de cepas constituem um valioso meio de mapear genes que afetam caracteres quantitativos complexos. Nós estudamos a variabilidade genética do intercruzamento das cepas procriadas por endogamia de camundongos Large (LG/J) e Small (SM/J), como um guia para estudos de mapeamento gênico. Dez machos SM/J foram cruzados com 10 fêmeas LG/J, após o que os animais foram acasalados aleatoriamente para produzir as gerações intercruzadas F1, F2 e F3. Os 1632 animais da geração F3 das 200 famílias de irmãos completos foram usados para calcular a herdabilidade e as correlações genéticas dos caracteres medidos. Um subgrupo de famílias foi submetido a adoção cruzada após o nascimento, para permitir a avaliação da importância dos efeitos maternos pós-natais. Foram coletados dados semanais de peso corporal da 1ª à 10ª semanas, assim como dados de necropsia do peso corporal, peso de órgãos, peso do coxim gorduroso reprodutor e comprimento de cauda nas gerações intercruzadas. Não houve heterose para pesos específicos para idade ou caracteres de necropsia, exceto pelo fato de que o peso da 1ª semana foi o maior na geração F2, indicando heterose dos efeitos maternos nas mães da geração F1. Encontramos herdabilidade moderada/alta para a maioria dos pesos esp...

Correlated responses to selection for large body size in oMt1a-oGH transgenic mice: organ traits

“…Positive correlated responses in liver, spleen, kidney and heart weights have been observed previously in lines selected for large body weight (Nash and Logsdon, 1978;Bünger et al, 1985). The correlated responses are in agreement with moderately high positive genetic correlations of these respective organ weights with adult body weight (Eisen and Johnson, 1981;Kramer et al, 1998). The absence of a zinc effect on correlated responses in organ weights indicates that 25 mM ZnSO 4 is not having any detrimental influences on organ growth as related to selection for overall body growth.…”

Fine-mapping quantitative trait loci affecting murine external ear tissue regeneration in the LG/J by SM/J advanced intercross line

“…The F1 hybrids were intercrossed to produce a F2 hybrid generation where each individual is a genetically unique recombination of the parental genotypes (Kramer et al, 1998;Vaughn et al, 1999). Two hundred pairs of F2 hybrids were randomly mated to form a F3 generation of 1600 individuals in 200 full-sibships (Kramer et al, 1998;Fawcett et al, 2008).…”

Change in maternal environment induced by cross-fostering alters genetic and epigenetic effects on complex traits in mice

“…These F 1 individuals were randomly mated to produce 510 F 2 animals and random mating among F 2 animals yielded 200 full-sib families of the F 3 generation with a total of 1632 individuals. Half-litters were reciprocally cross-fostered between litters born on the same day for 158 of the 200 F 3 litters (Kramer et al 1998). We analysed weekly weight from week 1 to week 10 and two growth periods: preweaning growth from weeks 1 to 3 and postweaning growth from weeks 3 to 10.…”