We are excited to share our work on molar #EvoDevo 🦷 in mouse and hamster 🐁, led by the amazing team of Marie Sémon and Sophie Pantalacci. We find an inverted hourglass pattern, with a maximum of evolutionary divergence at the bell stage. www.biorxiv.org/content/10.1... @lbmcinlyon.bsky.social - ThreadSky

marcrr.bsky.social • 31 days ago

We are excited to share our work on molar #EvoDevo 🦷 in mouse and hamster 🐁, led by the amazing team of Marie Sémon and Sophie Pantalacci. We find an inverted hourglass pattern, with a maximum of evolutionary divergence at the bell stage.
https://www.biorxiv.org/content/10.1101/2025.01.23.634446v1
@lbmcinlyon.bsky.social

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mads100tist.bsky.social•30 days ago

Did you know, in Spain "molar" also means "to be cool". So this paper is in and on itself, cool (congrats!!)

marcrr.bsky.social•31 days ago

Molar EvoDevo is interesting because there is a clear link between form and function, and variation has a strong adaptive potential. Moreover, as tooth development is well characterised, we can link patterns to gene properties and to developmental processes.

marcrr.bsky.social•31 days ago

We obtained RNAseq from tooth germs over the embryonic and postnatal period where the major events of morphogenesis occur, from bud, to cap, to bell stage until differentiation and enamel/dentin secretion, and obtained clusters of coexpressed genes per stage.

marcrr.bsky.social•31 days ago

As expected under coevolution upper and lower molars of the same species have very similar gene expression.
As expected from rapid molar evolution, mouse and hamster gene have rather different gene expression.
More surprising the coexpression clusters are most divergent in middle molar development.

marcrr.bsky.social•31 days ago

We found a similar pattern in selection on protein coding genes, with lower selective pressure (dN/dS) and higher positive selection (branch-site test) in middle development of molars.

marcrr.bsky.social•31 days ago

What explains this pervasive pattern? There are major differences both in proportions of highly expressed genes, and in expression specificity of genes. Highly expressed genes are known to be under stronger selection, which is also expected for more broadly expressed genes.

marcrr.bsky.social•31 days ago

Broad or narrow expression were measured both from tooth single-cell (cell-type specificity) and from organ-level bulk data (organ-specificity) @bgee.org. In a first approximation broadly expressed genes are expected to be more pleiotropic, thus under stronger selection.

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