Defective Gpsm2/G\u03b1i3 signalling disrupts stereocilia development and growth cone actin dynamics in Chudley-McCullough syndrome

Stephanie A Mauriac,Andrew Forge,Bernd Nürnberg,Maite M Moreau,Thomas B Friedman,Chantal Medina,Sze Chim Lee,Steve Dos-Santos Carvalho,Jonathan E Bird,Nathalie Sans,Sandra Beer-Hammer,Jean-Michel Blanc,Lukas Rüttiger,Ronan Peyroutou,Mireille Montcouquiol,Aysegul Gezer,Yeri E Hien,Olivier Thoumine

doi:10.1038/ncomms14907

Abstract

Mutations in GPSM2 cause Chudley-McCullough syndrome (CMCS), an autosomal recessive neurological disorder characterized by early-onset sensorineural deafness and brain anomalies. Here, we show that mutation of the mouse orthologue of GPSM2 affects actin-rich stereocilia elongation in auditory and vestibular hair cells, causing deafness and balance defects. The G-protein subunit Gαi3, a well-documented partner of Gpsm2, participates in the elongation process, and its absence also causes hearing deficits. We show that Gpsm2 defines an ∼200 nm nanodomain at the tips of stereocilia and this localization requires the presence of Gαi3, myosin 15 and whirlin. Using single-molecule tracking, we report that loss of Gpsm2 leads to decreased outgrowth and a disruption of actin dynamics in neuronal growth cones. Our results elucidate the aetiology of CMCS and highlight a new molecular role for Gpsm2/Gαi3 in the regulation of actin dynamics in epithelial and neuronal tissues.

Highlights

Mutations in GPSM2 cause Chudley-McCullough syndrome (CMCS), an autosomal recessive neurological disorder characterized by early-onset sensorineural deafness and brain anomalies
Multicolour STimulated Emission Depletion (STED) nanoscopy was used to probe the stereocilia tip compartment and revealed that Gpsm[2] was concentrated into a circular cap-like structure (Fig. 1f–h), similar to what was described for myosin 15, above the actin core labelled with phalloidin
Using fluorescence intensity line-scans along individual long stereocilia labelled with Gpsm[2] and Eps[8] antibodies and using the full-width at half-maximum (FWHM), we estimated that the tip domain extended B200 nm axially at the stereocilia tip (Gpsm[2] FWHM 1⁄4 198±59 nm, n 1⁄4 10; Eps[8] FWHM 1⁄4 200±63 nm, n 1⁄4 10)

Summary

Introduction

Mutations in GPSM2 cause Chudley-McCullough syndrome (CMCS), an autosomal recessive neurological disorder characterized by early-onset sensorineural deafness and brain anomalies. We demonstrated that Gpsm[2] and one of its binding partner, the a-subunit of the heterotrimeric G-protein Gi3 (Gai[3] encoded by Gnai3), control the asymmetric localization of the kinocilium in developing postmitotic hair cells (HCs) of the mammalian cochlea[6,7]. These results were confirmed by another group that reported an accumulation of both proteins at the tip of the hair bundles of the HCs8,9. Defects in all three genes individually cause abnormally short stereocilia[19,20,21,22], deafness in mice[19,21,23] and non-syndromic human deafness[24,25,26]

Methods

Results

Conclusion