LRRK2 mediates axon development by regulating Frizzled3 phosphorylation and growth cone–growth cone communication

Abstract

Axon–axon interactions are essential for axon guidance during nervous system wiring. However, it is unknown whether and how the growth cones communicate with each other while sensing and responding to guidance cues. We found that the Parkinson’s disease gene, leucine-rich repeat kinase 2 (LRRK2), has an unexpected role in growth cone–growth cone communication. The LRRK2 protein acts as a scaffold and induces Frizzled3 hyperphosphorylation indirectly by recruiting other kinases and also directly phosphorylates Frizzled3 on threonine 598 (T598). InLRRK1orLRRK2single knockout,LRRK1/2double knockout, andLRRK2 G2019Sknockin, the postcrossing spinal cord commissural axons are disorganized and showed anterior–posterior guidance errors after midline crossing. Growth cones from eitherLRRK2knockout orG2019Sknockin mice showed altered interactions, suggesting impaired communication. Intercellular interaction between Frizzled3 and Vangl2 is essential for planar cell polarity signaling. We show here that this interaction is regulated by phosphorylation of Frizzled3 at T598 and can be regulated by LRRK2 in a kinase activity-dependent way. In theLRRK1/2double knockout orLRRK2 G2019Sknockin, the dopaminergic axon bundle in the midbrain was significantly widened and appeared disorganized, showing aberrant posterior-directed growth. Our findings demonstrate that LRRK2 regulates growth cone–growth cone communication in axon guidance and that both loss-of-function mutation and a gain-of-function mutation (G2019S)cause axon guidance defects in development.