biostudies-literatureThomson LWellcome TrustBiotechnology and Biological Sciences Research CouncilEngineering and Physical Sciences Research Council203748https://www.ebi.ac.uk/biostudies/studies/S-EPMC7612712biostudies-literatureUnknown168In vertebrate embryos the presomitic mesoderm becomes progressively segmented into somites at the anterior end while extending along the anterior-posterior axis. A commonly adopted model to explain how this tissue elongates is that of posterior growth, driven in part by the addition of new cells from uncommitted progenitor populations in the tailbud. However, in zebrafish, much of somitogenesis is associated with an absence of overall volume increase, and posterior progenitors do not contribute new cells until the final stages of somitogenesis. Here, we perform a comprehensive 3D morphometric analysis of the paraxial mesoderm and reveal that extension is linked to a volumetric decrease and an increase in cell density. We also find that individual cells decrease in volume over successive soCells & developmentThe zebrafish presomitic mesoderm elongates through compaction-extension.PMC7612712EP/R025398/11804952109408/Z/15/Z109408Muresan LSteventon BThomson LfalseThe zebrafish presomitic mesoderm elongates through compaction-extension.In vertebrate embryos the presomitic mesoderm becomes progressively segmented into somites at the anterior end while extending along the anterior-posterior axis. A commonly adopted model to explain how this tissue elongates is that of posterior growth, driven in part by the addition of new cells from uncommitted progenitor populations in the tailbud. However, in zebrafish, much of somitogenesis is associated with an absence of overall volume increase, and posterior progenitors do not contribute new cells until the final stages of somitogenesis. Here, we perform a comprehensive 3D morphometric analysis of the paraxial mesoderm and reveal that extension is linked to a volumetric decrease and an increase in cell density. We also find that individual cells decrease in volume over successive so2021-01-01T00:00:00Z2021 Dec2025-04-21T21:26:12.758Z2025-02-19T04:05:00.839ZS-EPMC76127123459784610.1016/j.cdev.2021.203748