Femoral morphometry and femur length in mice selected for different body conformations. A potential animal model suitable for QTLs mapping

Abstract. Four lines of mice derived from the CBi stock, selected for different body conformations (CBi-, low body weight – short tail; CBi+, high body weight – long tail; CBi/L, low body weight – long tail; CBi/C, high body weight – short tail), differ in the biomass sustained per unit of skeleton weight. Femur length was modified in response to artificial selection either for high or low skeleton length. This feature suggests that these lines could be discriminated using the morphometric profile of their femurs. The femurs were obtained from both sexes at 15 weeks of age. A total of 16 measurements were taken on each bone. Genotype and gender effects for almost all measurements (P<0.001) were seen. Genotype x gender interactions (P<0.05) for some length measurements were also found. For sexual dimorphic characters, males had wider and shorter femurs than females. The results of principal components and discriminant analysis showed that the morphometric profile of the femur is a reliable and accurate means of identifying these inbred strains of mice as all female and male animals were assigned to the correct genotype. When the reciprocal hybrids among these genotypes were performed different responses in femur length were observed. So, the underlying genetic differences to this phenotypic differentiation emerge, at least partially, as a consequence of the exploitation of different sources of genetic variation for the trait in each selective procedure, jointly with the effect of simultaneously acting dispersive processes suggesting the potential usefulness of these genotypes as an animal model suitable for the identification of QTLs associated with femur growth.