Possible mechanisms for initiating macroscopic left-right asymmetry in developing organisms

TL;DR

This paper explores potential physical mechanisms, especially cytoskeletal forces, that could explain how microscopic molecular handedness leads to the macroscopic left-right asymmetry observed in developing organisms, highlighting current uncertainties.

Contribution

It proposes possible physical scenarios involving cytoskeletal forces for establishing body asymmetry, emphasizing the limited understanding in vertebrates and the need for further research.

Findings

Cytoskeletal forces may influence L/R asymmetry

Biological diffusion and gene regulation are insufficient alone

Current knowledge on vertebrate asymmetry is incomplete and debated

Abstract

How might systematic left-right (L/R) asymmetry of the body plan originate in multicellular animals (and plants)? Somehow, the microscopic handedness of biological molecules must be brought up to macroscopic scales. Basic symmetry principles suggest that the usual "biological" mechanisms -- diffusion and gene regulation -- are insufficient to implement the "right-hand rule" defining a third body axis from the other two. Instead, on the cellular level, "physical" mechanisms (forces and collective dynamic states) are needed involving the long stiff fibers of the cytoskeleton. I discuss some possible scenarios; only in the case of vertebrate internal organs is the answer currently known (and even that is in dispute).