A mechanical model of early somite segmentation

Priyom Adhyapok; Agnieszka M Piatkowska; Michael J Norman; Sherry G Clendenon; Claudio D Stern; James A Glazier; Julio M Belmonte

doi:10.1016/j.isci.2021.102317

A mechanical model of early somite segmentation

iScience. 2021 Mar 16;24(4):102317. doi: 10.1016/j.isci.2021.102317. eCollection 2021 Apr 23.

Authors

Priyom Adhyapok^{1

2}, Agnieszka M Piatkowska³, Michael J Norman^{4

5}, Sherry G Clendenon^{1

6}, Claudio D Stern³, James A Glazier^{1

6}, Julio M Belmonte^{4

5}

Affiliations

¹ Biocomplexity Institute, Indiana University, Bloomington, IN 47405, USA.
² Department of Physics, Indiana University, Bloomington, IN 47405, USA.
³ Department of Cell and Developmental Biology, University College London, London WC1E 6BT, United Kingdom.
⁴ Department of Physics, North Carolina State University, Raleigh, NC 27607, USA.
⁵ Quantitative and Computational Developmental Biology Cluster, North Carolina State University, North Carolina, USA.
⁶ Department of Intelligent Systems Engineering, Indiana University, Bloomington, IN 47405, USA.

Abstract

Somitogenesis is often described using the clock-and-wavefront (CW) model, which does not explain how molecular signaling rearranges the pre-somitic mesoderm (PSM) cells into somites. Our scanning electron microscopy analysis of chicken embryos reveals a caudally-progressing epithelialization front in the dorsal PSM that precedes somite formation. Signs of apical constriction and tissue segmentation appear in this layer 3-4 somite lengths caudal to the last-formed somite. We propose a mechanical instability model in which a steady increase of apical contractility leads to periodic failure of adhesion junctions within the dorsal PSM and positions the future inter-somite boundaries. This model produces spatially periodic segments whose size depends on the speed of the activation front of contraction (F), and the buildup rate of contractility (Λ). The Λ/F ratio determines whether this mechanism produces spatially and temporally regular or irregular segments, and whether segment size increases with the front speed.

Keywords: Developmental Biology; Mechanical Modeling; Poultry Embryology.