ALS-causative mutations in FUS/TLS confer gain- and loss-of-function by altered association with SMN and U1-snRNP. Homo sapiens

The RNA-binding protein FUS/TLS, mutation in which is causative of the fatal motor neuron disease ALS, is demonstrated to directly bind to the U1-snRNP and SMN complexes. ALS-causative mutations in FUS/TLS are shown to abnormally enhance their interaction with SMN and reduce interaction with U1-snRNP. Correspondingly, global RNA analysis reveals a mutant-dependent loss of splicing activity, with ALS-linked mutants failing to reverse changes caused by loss of wild-type FUS/TLS. Furthermore, a common FUS/TLS mutant-associated RNA splicing signature is identified in ALS patient fibroblasts. Taken together, our studies establish potentially converging disease mechanisms in ALS and spinal muscular atrophy, with ALS-causative mutants acquiring properties representing both gain (dysregulation of SMN) and loss (reduced RNA processing mediated by U1-snRNP) of function. Overall design: RNA-mediated oligonucleotide Annealing, Selection, and Ligation with Next-Generation sequencing (RASL-seq) method was used for analyzing alternative splicing changes. Oligonucleotide probes are designed to anneal to the exon-exon junctions. The probe library was assembled to assess 5530 unique alternative splicing events, most of which were exon inclusion or skipping, with a minority for alternative 5’- or 3’- splice sites. The splicing changes were compared among groups of reducing FUS/TLS or SMN levels, or expressing various FUS mutations to determine the loss versus gain of FUS/TLS function on splicing regulation.