Congenital muscle dystrophy and diet consistency affect mouse skull shape differently

Area of Science:

• Developmental biology
• Craniofacial morphology
• Musculoskeletal system

Background:

• Mammalian skull bones exhibit plasticity in response to masticatory function.
• The influence of muscle function on skull growth and regional development is not fully understood.

Purpose of the Study:

• To investigate the impact of altered muscle function (pre- or post-weaning) on adult mouse skull shape and masticatory muscle mass.
• To compare the effects of congenital muscle dystrophy and diet on craniofacial development.

Main Methods:

• Utilized muscle dissection and 3D landmark-based geometric morphometrics.
• Compared temporalis and masseter muscle mass and skull shape in dystrophic (mdx) and wild-type (wt) mice.
• Assessed effects of hard vs. soft diets on skull and muscle morphology.

Main Results:

• Congenital muscle dystrophy (mdx) resulted in a flattened neurocranium, dorsally displaced foramen magnum, and anteriorly placed mandibular condyle compared to wild-type (wt) mice.
• Soft diet led to reduced masseter muscle mass, more gracile facial features, and labially inclined incisors, indicating decreased bite strength.
• The early-maturing neurocranium and posterior mandible were affected by dystrophy, whereas the late-maturing face and anterior mandible responded to diet independently of the mdx mutation.

Conclusions:

• The skull exhibits a hierarchical, tripartite organization (neurocranium, face, mandible) with modular divisions based on development and function.
• Masticatory loading is a significant environmental factor influencing craniofacial variation.
• Developmental timing and genetic factors interact with environmental stimuli to shape skull morphology.