Identification of biallelic intronic EPM2A mutations in a Lafora disease kindred

Abstract

Lafora disease (LD) is a severe autosomal recessive disease, which usually presents as seizure and myoclonus, followed by behavioral changes, dysarthria, intellectual decline, and finally progressed to dementia and a vegetative state. The main cause of LD is the loss-of-function mutations in EPM2A and NHLRC1 that encode laforin and malin, respectively. Targeted genetic testing is the gold standard to confirm the diagnosis of LD. To describe the pathogenic role of biallelic EPM2A intronic mutations carried by patients in a family diagnosed as LD. Here, we present clinical findings in a patient presenting with epileptic seizures and Lafora bodies in muscle biopsy. Long-read DNA and RNA sequencing were performed to identify the causative mutation. Western blot and qPCR confirmed the pathogenic role of biallelic EPM2A intronic mutations. Genetic testing identified two intronic mutations in EPM2A which caused aberrant mRNA splicing. c.301+1 G > A in EPM2A caused aberrant splicing at donor site and resulted in intron retention in transcript NM_005670.4, while c.476+14860 C > A caused aberrant splicing in transcript NM_001368129.2 and NM_001368132.1. Our findings expand the spectrum of variants in LD disease, additionally providing evidence linking non-coding regulatory regions mutations to LD disease.