A human DCC variant causing mirror movement disorder reveals an essential role for the Wave regulatory complex in Netrin/DCC signaling

The axon guidance cue, Netrin-1, signals through its receptor DCC to attract commissural axons to the midline. Pathogenic variants in DCC frequently lead to congenital mirror movements (CMM), but how these variants impact DCC function is largely unknown. Screening of DCC in individuals with CMM recently revealed a novel variant located in a conserved motif in the cytoplasmic tail of DCC that is predicted to bind to a central actin nucleation promoting factor, the WAVE regulatory complex (WRC). Here, we use biochemical and axon guidance assays to show that this CMM-associated DCC variant is pathogenic by disrupting the interaction between DCC and the WRC. This DCC-WRC interaction is evolutionarily conserved and is required for Netrin-1 mediated commissural axon outgrowth and guidance. Together, we identify the WRC as a pivotal component of Netrin-1/DCC signaling and further provide a molecular mechanism explaining how genetic variants in DCC may lead to CMM.