ABSTRACT
Spiral ganglion neurons (SGNs) carry sound information from the cochlea to the hindbrain, and innervate either inner or outer hair cells. Type II SGNs (SGNIIs) extend peripheral afferents towards outer hair cells, which make a characteristic 90° turn towards the cochlear base and innervate multiple outer hair cells. It has been shown that the planar cell polarity (PCP) pathway acts non-autonomously in the cochlear epithelium to guide SGNII peripheral afferent turning. However, the underlying mechanisms are unknown. Here, we show that PCP signaling regulates junctional localization of the small GTPase Rac1 and the cell adhesion molecule Nectin3 in mouse cochlear supporting cells (SCs), which serve as intermediate targets of SGNII peripheral afferents. Loss of Rac1 or Nectin3 partially phenocopied SGNII peripheral afferent turning defects in Vangl2 mutants. We present evidence that Rac1 plays a non-autonomous role in part by regulating the localization of core PCP proteins Vangl2 and Dvl3 at the SC–SC junctions, while Nectin3 likely serves a cell adhesion function to control SGNII afferent turning. Together, these experiments identify Nectin3 and Rac1 as regulators of PCP-directed SGNII axon guidance in the cochlea.
Footnotes
Author contributions
Conceptualization: S.C., X.L.; Methodology: S.C., N.X., X.L.; Validation: S.C., X.L.; Formal analysis: S.C., N.X., T.E.M., J.W., A.A., E.F., Margaret Smith, P.W., Matthew Smith, A.H., X.L.; Investigation: S.C., N.X., A.A., E.F., A.S., X.L.; Resources: A.S., X.L.; Data curation: S.C., N.X., T.E.M., J.W., Margaret Smith, P.W., Matthew Smith, A.H., X.L.; Writing – original draft preparation: S.C., X.L.; Writing – review and editing: S.C., A.A., X.L.; Visualization: S.C., A.A., X.L.; Supervision: A.S., X.L.; Project administration: X.L.; Funding acquisition: S.C., A.S., X.L.
Funding
This work was supported by the National Institute on Deafness and Other Communication Disorders (F31-DC020667 to S.C.; R01-DC013773 to X.L.), the National Institute of Child Health and Human Development (R01-HD107872 to X.L. and A.S.), the National Institute of General Medical Sciences (T32-GM008136 to S.C.) and the University of Virginia (Double Hoo Award to S.C. and E.F.; Robert R. Wagner fellowship to S.C.). Deposited in PMC for release after 12 months.
Data and resource availability
All relevant data can be found within the article and its supplementary information.
