WILLMORE, K; LOZANOFF, S; ZELDITCH, M; HALLGRIMSSON, B; Univ. of Calgary; Univ of Hawaii, Honolulu; Univ. of Michigan; Univ. of Calgary: Direct and Indirect Developmental Effects of a Craniofacial Mutation in a Mouse Model

Mutations have been shown to disrupt development directly by creating obvious phenotypic deviations that occur in all individuals with the mutation. It is less well known how the degree of phenotypic variability might indirectly be affected by mutations. In this study, we look at the effects of the Brachyrrhine (Br) mutation in a mouse model on the degree of within-individual cranial variability or fluctuating asymmetry, and among-individual variability. The Br mutation targets the sphenoid and heterozygote Br mice display a shortened midface and a globular cranial vault as compared to their wildtype littermates. We hypothesized that mutants with this obvious phenotypic malformation would also exhibit increased phenotypic variation as compared with wildtype mice. 3D landmarks were collected from cranial images for 120 mice captured using computed microtomography. We used a battery of univariate and multivariate tests to compare the degree of among-individual and within-individual variance between mutant and wildtype groups of mice. Our results indicate that there is significantly greater variation between individuals in the mutant group, however variation within individuals is not significantly different for the two groups. These results suggest that in addition to the predictable developmental disruption to overall cranial morphology observed in these mutant mice, we might also expect greater susceptibility to other perturbations as a result of the increased variation.