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Canalization and developmental stability in the Brachyrrhine mouse.
Katherine Elizabeth Willmore1, Miriam Leah Zelditch, Nathan Young
1Department of Medical Sciences, University of Calgary, Alberta, Canada.
Journal of Anatomy
|March 15, 2006
Summary
The Br mutation impacts mouse skull shape, affecting facial and cranial development. This genetic change increases skull variability, particularly in the basicranium, suggesting altered developmental mechanisms.
Area of Science:
- Developmental biology
- Genetics
- Craniofacial morphology
Background:
- The semi-dominant Br mutation in mice causes distinct craniofacial abnormalities, including retrognathism and a globular neurocranial vault in heterozygotes.
- Understanding the spatial extent of this mutation's effects on skull shape and variability is crucial for elucidating its developmental impact.
Purpose of the Study:
- To investigate the skull-wide effects of the Br mutation on overall skull shape and regional morphology.
- To analyze patterns of shape variability, including variance and fluctuating asymmetry, across the skull and its components in Br heterozygotes compared to wildtype mice.
Main Methods:
- Comparative geometric morphometrics was used to analyze skull shape in Br heterozygote mice and wildtype littermates.
- Statistical analyses were performed to compare mean shapes and patterns of variation (variance, fluctuating asymmetry) between the two groups across the whole skull, basicranium, face, and neurocranium.
Main Results:
- Br heterozygotes exhibited significant differences in skull shape compared to wildtype mice across all analyzed regions (basicranium, face, neurocranium) and the skull as a whole.
- A significant increase in variance and fluctuating asymmetry was specifically observed in the basicranium of Br mutant mice.
- Phenotypic changes in mean shape and variance were localized to the same anatomical region, the basicranium.
Conclusions:
- The Br mutation significantly alters the developmental architecture of the mouse skull, leading to changes in both mean shape and phenotypic variability.
- The observed increase in variability and asymmetry is localized to the basicranium, suggesting that the developmental mechanisms driving the mean shape change also influence variance in that region.
- These findings highlight a link between the developmental basis of mean phenotypic change and the generation of phenotypic variance.