Mechanosignaling in vertebrate development

Myriads forces are at play during morphogenesis. Their concerted activity shapes individual cells, tissues and the whole embryo, representing the most awe-inspiring marvel of developmental biology. In spite of their prevalence, the potential instructive role of cell mechanics in fate determination and patterning has remained long neglected, in part due to the difficulties in translating the physical world of cells in molecular terms. The recent discovery of the principles of mechanotransduction, of how these impact on gene expression, is however starting to change this scenario, making mechanotransduction finally amenable to experimental dissection through genetics, molecular and bioengineering approaches. Here we review this emerging field, and a series of discoveries that potently bring back cell mechanics at the centerstage of vertebrate developmental biology. We discuss the role of actomyosin contractility as integrating platform between morphogens, lateral inhibition and mechanosignaling. We also review data indicating that supracellular pulling forces, coupled with solid-to-fluid changes in the material contexture of embryonic fields, may act as overarching mechanical "organizers". The evidence also indicates that a continuum of forces is what ultimately locks "self-organizing" movements with cell fate, from the earliest pre-implantation decisions to the fine details of organogenesis. Notably, similar mechanisms are reawakened in organoids and in adult tissues during regeneration. Developmental biology has been correctly depicted, but recently often forgotten, as the "mother" of all biological disciplines. Investigations in developmental mechanics may revamp interest, and have a broad impact in the fields of regenerative medicine, stem cells and cancer biology.