Identification ofRNF13as cause of recessively inherited ALS in a multi-case pedigree

Abstract

BackgroundAmyotrophic lateral sclerosis (ALS) is the most common motor neuron disease. The approximately 50 known ALS-associated genes do not fully explain its heritability, which suggests the existence of yet unidentified causative genes. We report results of studies aimed at identification of the genetic cause of ALS in a pedigree (three patients) without mutations in the common ALS-causative genes.MethodsClinical investigations included thorough neurological and non-neurological examinations and testings. Genetic analysis was performed by exome sequencing. Functional studies included identification of altered splicing by PCR and sequencing, and mutated proteins by western blot analysis. Apoptosis in the presence and absence of tunicamycin was assessed in transfected HEK293T cells using an Annexin-PE-7AAD kit in conjunction with flow cytometry.ResultsClinical features are described in detail. Disease progression in the patients of the pedigree was relatively slow and survival was relatively long. AnRNF13mutation was identified as the cause of the recessively inherited ALS in the pedigree. The gene is highly conserved, and its encoded protein (RING finger protein 13) can potentially affect various neurodegenerative-relevant functions, including protein homeostasis. TheRNF13splice site mutation caused expression of two mis-spliced forms ofRNF13mRNA and an aberrant RNF13 protein, and affected apoptosis.ConclusionRNF13was identified as a novel causative gene of recessively inherited ALS. The gene affects protein homeostasis, which is one of most important components of the pathology of neurodegeneration. The contribution ofRNF13to the aetiology of another neurodegenerative disease is discussed.