Divergent roles of ALS-linked proteins FUS/TLS and TDP-43 intersect in processing long pre-mRNAs (RNA-Seq)

FUS/TLS and TDP-43 are RNA/DNA-binding proteins integrally involved in amyotrophic lateral sclerosis (ALS) and frontal temporal dementia. FUS/TLS is shown to bind RNAs from >5,500 genes in mouse and human brain, primarily through a GUGGU binding motif. A characteristic sawtooth-like binding pattern is identified, supporting co-transcriptional deposition of FUS/TLS. Depletion of FUS/TLS from the adult nervous system is shown to alter levels or splicing of >970 mRNAs, most of which are distinct from the RNAs whose maturation is dependent on TDP-43. Nonetheless, only 55 RNAs are reduced upon depletion of either TDP-43 or FUS/TLS from mouse brain and human neurons differentiated from pluripotent stem cells, including mRNAs transcribed from genes with exceptionally long introns and that encode proteins essential for neuronal integrity. A subset of these is significantly lowered in FUS/TLSR521G and TDP-43G298S mutant fibroblasts and in TDP-43 aggregate-containing motor neurons in sporadic ALS, evidence pointing to a common loss-of-function pathway as one component underlying motor neuron death from misregulation of TDP-43 or FUS/TLS.