Smn-1interacts With Uaf-1to Regulate Caenorhabditis Elegans Lifespan And Motor Function

Spinal muscular atrophy (SMA), the most frequent lethal neuromuscular disorder, is caused by loss-of-function mutations in survival motor neuron gene SMNl. However, the mechanism is still unclear. Previous studies found mutations in SMNl could affect assembly of U snRNPs, which are large complexes to carry out pre-mRNA splicing. Defective pre-mRNA splicing is hypothesized as a major cause of SMA.Objective:To study the molecular function of smn-1, the C. elegans ortholog of SMNl, in pre-mRNA splicing and analyze the interaction between smn-1and uaf-1which encodes an important splicing factor recognizing3’ splice site.Methods:1.tos-1is a sensitive endogenous splicing reporter. The splicing of tos-1is examined by RT-PCR in smn-1(ok355△) null mutants. We also examined tos-1splicing in animals fed dsRNAs (double-stranded RNAs) targeting smn-1. Splice site substitution experiments were used to test whether smn-1is required for efficient splicing at strong3’splice site.2.smn-1(ok355△) mutation produces a pleiotropic phenotype including late larval arrest, reduced lifespan as well as impaired locomotion and pharyngeal activity. To study the interaction between smn-1and uaf-1, we measured the lifespan, bodybends, thrashing and pharyngeal pumping of the related strains.3.U snRNAs are the core components of U snRNPs. There are five U snRNAs participating pre-mRNA splicing, including U1, U2, U4, U5and U6snRNAs. We examined the expression of these U snRNAs in smn-1(ok355△) mutants using RT-qPCR.Results:l.smn-1(ok355A) mutation causes altered splicing of tos-1, the splicing of weak3’splice site requires smn-1, while the splicing of strong3’splice site does not.2.Mutations of uaf-1extend the lifespan and improve the motor functions of smn-1(ok355△) mutants.3.In smn-1null mutants we detected a reduced expression of U1and U5snRNAs and an increased expression of U2, U4and U6snRNAs.Conclusions:The proper splicing of pre-mRNA requires the normal function of smn-1, and smn-1is an important splicing factor in C. elegans. uaf-1is a novel modifier of smn-1, they interact with each other to regulate C. elegans lifespan and motor function, smn-1null mutation differentially affect the expression of spliceosomal snRNAs.