Mechanical stretch scales centriole number to apical area via Piezo1 in multiciliated cells.

Saurabh Kulkarni,Priya Date,Mustafa K Khokha,Rosa Ventrella,Brian J Mitchell,Jonathan Marquez

doi:10.7554/elife.66076

Abstract

How cells count and regulate organelle number is a fundamental question in cell biology. For example, most cells restrict centrioles to two in number and assemble one cilium; however, multiciliated cells (MCCs) synthesize hundreds of centrioles to assemble multiple cilia. Aberration in centriole/cilia number impairs MCC function and can lead to pathological outcomes. Yet how MCCs control centriole number remains unknown. Using Xenopus, we demonstrate that centriole number scales with apical area over a remarkable 40-fold change in size. We find that tensile forces that shape the apical area also trigger centriole amplification based on both cell stretching experiments and disruption of embryonic elongation. Unexpectedly, Piezo1, a mechanosensitive ion channel, localizes near each centriole suggesting a potential role in centriole amplification. Indeed, depletion of Piezo1 affects centriole amplification and disrupts its correlation with the apical area in a tension-dependent manner. Thus, mechanical forces calibrate cilia/centriole number to the MCC apical area via Piezo1. Our results provide new perspectives to study organelle number control essential for optimal cell function.

Highlights

Organelles compartmentalize cells into discrete functioning units
We employed four different approaches to increase the apical area of multiciliated cells (MCCs). 99 First, two species of Xenopus are common models for cell biology (X. laevis and X. tropicalis), and due to the evolutionary variation in embryonic sizes of the two species, they are useful for scaling experiments (Figure 1d – compare relative sizes of the eggs and embryo) (Levy & Heald, 2012)
Moving forward, we focused on the hypothesis that the apical area may fine tune centriole number. 171 While we initially focused on the number of centrioles at the apical surface, this may not 172 reflect the total number of centrioles in the cell

Summary

INTRODUCTION

Organelles compartmentalize cells into discrete functioning units. Cells must regulate the number of organelles to achieve proper function (Marshall, 2007, 2016; Nigg & Holland, 2018; Rafelski & Marshall, 2008). Of too few or too many cilia impairs MCC function and is associated with several diseases including Primary Ciliary Dyskinesia, suggesting the existence of an active mechanism that controls cilia number (Boon et al, 2014; Spassky & Meunier, 2017; Wallmeier et al, 2014). As MCCs intercalate into the outer epithelial cell layer and expand their apical surface, centrioles migrate apically, dock at the apical surface, and provide the platform for assembly of motile cilia (Figure 1a, Steps 1-4) (Deblandre, Wettstein, Koyano-Nakagawa, & Kintner, 1999; Kulkarni, Griffin, Date, Liem, & Khokha, 2018; Stubbs, Davidson, Keller, & Kintner, 2006; Zhang & Mitchell, 2015). In this study, we focused our efforts on counting centrioles as a simple, efficient proxy for cilia number using chibby-GFP, a marker for mature centrioles (Burke et al, 2014)

RESULTS AND DISCUSSION

399 ACKNOWLEDGEMENTS

MATERIALS AND METHODS

Methods