The Research On Gene Mutation Analysis Of SPG4 And SPG3A In Hereditary Spastic Paraplegia Patients

Background Hereditary spastic paraplegias (HSPs or SPGs) are a heterogeneous group of inherited neurodegenerative disorders characterized by slowly progressive spasticity and weakness of the lower extremities. They are divided into pure and complicated forms depend on whether the paraparesis exists in isolation or with other major clinical features, such as dementia, mental retardation, ataxia, deafness, epilepsy, peripheral neuropathy, extrapyramidal disturbances, and skin lesions. The pathologic changes is mainly the degeneration in the corticospinal tract and the posterior funiculus. HSPs can be inherited in an autosomal dominant (AD), autosomal recessive (AR), or X-linked manner. So far, at least 37 distinct HSP loci designated SPG have been assigned with 19 disease-associated genes identified. SPG4 and SPG3A are the common subtypes, which account for 40% and 10% of AD-HSP patients, respectively. The rearrangment mutation on SPG4 gene have been reported abroad, however there was no rearrangment mutation detection of AD-HSP patients performed in Asia.Objective To investigate the mutation frequencies of SPG4 and SPG3A gene in AD and sporadic HSP patients in China; To establish multiplex ligation-dependent probe amplification (MLPA) platform for detecting rearrangment mutation of SPG4 and SPG3A gene.Methods PCR and direct sequencing were carried out to detect the micro-mutation of spastin and atlastin gene in 21 AD-HSP patients and 44 isolated cases in China; MLPA technology and capillary electrophoresis were undertook to detect rearrangment mutation of spastin and atlastin gene in 21 AD-HSP patients in China.Results 1. Five families had micro-mutations on SPG4 gene, and another five families carried rearrangment mutations of SPG4 gene. In addition, one individual had micro-mutation in 44 sporadic patients. We found 10 mutations on SPG4 gene, which comprised of 1 missenses, 2 nonsenses, 2 micro-deletions, 1 micro-insertion, 3 exon deletions and 1 exon duplication, and five mutations of them were novel. Among 11 SPG4 probands, 9 cases presented pure spastic paraplegia, and 2 cases showed complicated spastic paraplegia.2. One family and one isolated case had missense mutations on SPG3A gene, respectively. 1/2 missense mutations was novel. Two SPG3A probands also presented pure spastic paraplegia, and the SPG3A family showed incomplete penetrance.Conclusions1. First established the mutation detection platform for the rearrangment mutation on SPG4 and SPG3A gene by MLPA technique in China.2. The mutation frequencies of SPG4 were 47.6% in AD-HSP patients and 2.3% in isolated cases in Chinese Han people. 3. The mutation frequencies of SPG3A were 4.8% in AD-HSP patients and 2.3% in isolated cases in Chinese Han people.