Mutational spectrum of the SPAST and ATL1 genes in Korean patients with hereditary spastic paraplegia

Hereditary spastic paraplegia (HSP) is a genetically heterogeneous group of diseases characterized by insidiously progressive lower-extremity weakness and spasticity. Spastic paraplegia 4 (SPAST) is the most common type of uncomplicated autosomal dominant HSP (40% of such cases), and spastic paraplegia 3A (ATL1) is the second most common. Here, we conducted mutational analysis of the SPAST and/or ATL1 genes in 206 unrelated patients with HSP. DNA sequencing and multiplex ligation-dependent probe amplification was used to analyze SPAST or ATL1 pathogenic variants. To confirm splice-site pathogenic variants, mRNA transcripts were analyzed by reverse transcription-polymerase chain reactions and sequencing. Among the 52 patients with medical records and SPAST or ATL1 gene pathogenic variants or novel unclassified variants, 50 showed spasticity or weakness in their lower extremities. We identified 16 known and 18 novel SPAST pathogenic variants and 2 known and a novel splicing pathogenic variants in ATL1. We also identified 4 unclassified SPAST variants in 5 patients and an unclassified ATL1 variant in 1 patient. Further, a novel leaky-splicing variant (c.1537-11A>G) was found in SPAST, which caused skipping of exon 13 or exons 13-14. Among the 206 unrelated patients with HSP, SPAST or ATL1 pathogenic variants and potentially pathogenic variants were identified in 52 patients, a low pathogenic variant rate compared to previous results. Results from our study suggest that other genes may be involved in HSP in the Korean population.