MAPT and amyotrophic lateral sclerosis: cDNAs encoding WT human FUS (hFUSWT) or one of two mutant isoforms—hFUSR521C associated with typical, adult-onset ALS, and hFUSP525L found in patients with an aggressive, juvenile-onset form of the disease10—were introduced (Fig. 1a,b) into the first coding exon of tau, preceded by an N-terminal myc tag to label the exogenous hFUS protein.