The Investigation of Genetic and Clinical Features in Patients with Hereditary Spastic Paraplegia in Central-Southern China

Abstract

Objective Hereditary spastic paraplegias (HSPs) are a clinically and genetically heterogeneous group of neurodegenerative disorders. We describe the genetic and clinical features of a cohort of five HSP families from central-southern China. Methods Using targeted exome-sequencing technology, we investigated the genetic and clinical features in five HSP families. We review the clinical histories of these patients as well as the molecular and functional characterization of the associated gene variants. We also performed functional analyse of an intron variant of SPAST in vitro.Results We identified a known SPAST mutation (p.Pro435Leu) in a family with autosomal dominant HSP (AD-HSP) and four novel variants in three HSP families and a sporadic case. These identified four novel variants include a SPG11 nonsense variant (p.Val1979Ter), two B4GALNT1 variants (p.Ser475Phe and c.1002+2T>G), and a splicing site variant in SPAST (c.1245+5G>A). Minigene analysis of the SPAST splicing variant（c.1245+5G>A）revealed that the mutation resulted in mRNAs with a loss of exon 9. The SPG4 family carrying SPAST c.1245+5G>A exhibited obviously genetic anticipation, with a decreased age at onset and increased severity in successive generations. The proband with p.Val1979Ter variant in SPG11 showed characteristic clinical feature of early-onset, severe spasticity, and corpus callosum atrophy which were highly suggestive of the diagnosis of SPG11-associated HSP. Conclusions Our findings strongly support variable phenotype of B4GALNT1-related SPG26 and also expand the clinical and mutation spectrum of HSP caused by mutations in SPG4, SPG11, and B4GALNT1. These results will help to improve the efficiency of early diagnosis in patients clinically suspected of HSP.