Evolutionary modification of development in mammalian teeth: quantifying gene expression patterns and topography.

Area of Science:

• Evolutionary biology
• Developmental biology
• Genetics

Background:

• Mammalian dental morphology is key to evolutionary studies.
• Linking gene expression to morphological changes is crucial for understanding dental evolution.
• Teeth exhibit complex shapes, with evolution often involving subtle modifications.

Purpose of the Study:

• To investigate the association between genetic markers for enamel knots and the evolutionary divergence of molar teeth in mice and voles.
• To determine if molecular prepatterns predict morphological differences in developing teeth.

Main Methods:

• Utilized topographic methods with Geographic Information Systems (GIS).
• Analyzed expression patterns of Fgf4, Lef1, p21, and Shh genes.
• Correlated gene expression with digital elevation models of developing tooth shapes.

Main Results:

• Molecular prepatterns, specifically enamel knot gene expression, predict lateral cusp topography over a day in advance.
• Heterotopic shifts in molecular prepatterns are linked to the evolution of mouse molar cusp topography.
• Vole molar evolution involves accelerated longitudinal growth and iterative cusp addition without altering lateral cusp topography.

Conclusions:

• Subtle heterotopic shifts in molecular prepatterns significantly contribute to tooth cusp topography evolution.
• Iterative cusp addition in voles, post-lateral cusp topography establishment, may constrain evolutionary independence of morphological features.
• Diversity in mammalian molar patterns likely arises from heterotopic and iterative developmental processes.