How Do Cells Measure Length?

Abstract

Existence of cellular structures with specific size and length raises a fundamental question in biology: how do cells measure length? One conceptual answer to this question is a molecular ruler, but examples of such rulers in eukaryotes have been lacking. We recently identified a molecular ruler in eukaryotic cilia and flagella using genetic screening and cryo-electron tomography. We demonstrated that FAP59 and FAP172 form a 96-nm-long complex in Chlamydomonas flagella and the absence of the complex disrupted 96-nm repeats of axonemes. Furthermore, lengthening of the FAP59/172 complex resulted in extension of the repeats up to 128 nm.