GDPD5 and amyotrophic lateral sclerosis: Abnormal GDE2 protein distribution coincides with TDP-43 abnormalities in postmortem tissue of patients with ALS and with Wnt activation and TDP-43 dysfunction in iSN models of C9ALS, and functional studies in C9ALS iSNs provide evidence that Wnt activation is causal for TDP-43 loss of function.