Development Shapes a Consistent Inbreeding Effect in Mouse Crania of Different Line Crosses

Area of Science:

• Evolutionary biology
• Developmental biology
• Genetics

Background:

• Genetic variation underlies phenotypic diversity.
• Developmental processes influence how genetic differences manifest as trait variations.
• Shared developmental pathways may impose similar patterns on heritable variation.

Purpose of the Study:

• To investigate the role of developmental processes in patterning craniofacial shape variation.
• To analyze the effects of genetic variation on skull shape across different mouse strains and their crosses.
• To determine if nonadditive genetic effects structure phenotypic variation in a predictable manner.

Main Methods:

• Utilized geometric morphometrics and multivariate analysis to assess mouse skull shape.
• Employed a diallel cross design between eight inbred mouse strains from the Collaborative Cross Project.
• Analyzed F1 hybrid phenotypes to identify nonadditive deviations from midparental values.

Main Results:

• Craniofacial shape exhibited significant nonadditive genetic deviations, unlike body weight.
• Parental strain divergence showed high dimensionality in additive genetic effects.
• Nonadditive craniofacial shape deviations displayed lower dimensionality and a coherent directional pattern.

Conclusions:

• Developmental processes exert a strong structuring influence on the relationship between genotype and phenotype.
• A limited set of developmental mechanisms may govern the complex mapping of genetic variation to phenotypic form.
• The patterned nature of phenotypic variation is shaped by underlying developmental constraints.