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The brachymorph mouse and the developmental-genetic basis for canalization and morphological integration
Benedikt Hallgrímsson1, Jevon J Y Brown, Alice F Ford-Hutchinson
1Department of Cell Biology & Anatomy and the Joint Injury and Arthritis Research Group, University of Calgary, 3330 Hospital Dr., Calgary, AB, Canada T2N 4N1. bhallgri@ucalgary.edu
Evolution & Development
|January 18, 2006
Summary
The brachymorph (bm) mutation in Papps2 significantly increases craniofacial shape variation and morphological integration. This suggests developmental sensitivity to glycosaminoglycan sulfation levels, illustrating canalization.
Area of Science:
- Developmental biology
- Genetics
- Morphometrics
Background:
- Mutations can alter phenotypic variability, but mechanisms are poorly understood.
- The brachymorph (bm) mutation affects phosphoadenosine-phosphosulfate synthetase 2 (Papps2) and causes chondrocranium growth reduction due to undersulfated glycosaminoglycans (GAGs).
Purpose of the Study:
- To investigate the impact of the bm mutation on craniofacial shape variation and morphological integration.
- To explore the relationship between GAG sulfation levels and developmental sensitivity in chondrocranial development.
Main Methods:
- Analysis of craniofacial shape variation patterns in brachymorph mutants.
- Assessment of phenotypic variance and morphological integration in the chondrocranium.
- Inference of developmental influences based on observed variations in GAG sulfation.
Main Results:
- The bm mutation significantly increases phenotypic variance and morphological integration of craniofacial shape, particularly in the basicranium.
- An altered pattern of craniofacial shape variation suggests mutation-induced developmental influences.
- Chondrocranial development shows increased sensitivity to variations in chondroitin sulfate sulfation at low levels.
Conclusions:
- The bm mutation alters craniofacial development by affecting GAG sulfation, leading to increased shape variation and integration.
- Variable expressivity of the mutation, influenced by genetic, environmental, or intrinsic factors, underlies the observed phenotypic variability.
- Chondrocranial development is sensitive to sulfation levels, demonstrating canalization in response to developmental perturbations.