Genetic Analysis Of SPG4(SPAST)and SPG3A (ATL1) Genes In Hereditary Spastic Paraplegia Patients

Background:Hereditary spastic paraplegia （SPG or HSP） is a clinically and genetically heterogeneous group of neurodegenerative disorders that are clinically characterised by progressive muscle stiffness and weakness of the lower-limbs. Strumpell and Lorrain published HSP in great detail which is considered to be the land-mark description, following the first report by Seeligmuller （1876）. Hence, HSP is primarily known as Strumpell-Lorrain disease. The prevalance of HSP/100000varies from2.7to9.6. According to the phenotype, HSP is classified as either "pure", characterised by progressive muscle stiffness, weakness, hyperreflexia and spasticity of the lower limbs, and occasionally bladder dysfunction or vibratory sense impairment, or as "complex"（complicated）, in addition to the "pure" phenotype, characterised by more extensive neurological and non-neurological manifestations with or without abnormal findings such as mental retardation, extrapyramidal disturbances, ataxia, epilepsy, optic atrophy, retinitis pigmentosa, deafness, cataract, amyotrophy, peripheral neuropathy or skin lesions. Genetically, HSPs follow autosomal-dominant （AD-HSP）, autosomal-recessive （AR-HSP）, X-linked （XL-HSP）, and maternal trait of inheritance. AD-HSP is the most common pattern and40-45%of patients carry mutations in the SPAST-gene （SPG4） and10%in the ATL1-gene （SPG3A）. In recent years, it has been recognized that SPG4and SPG3A are caused by micro-mutations in the SPAST and ATL1, as well as by rearrangement mutations. Objective:1、To establish a polymerase chain reaction （PCR） and direct sequencing platform for detecting micro-mutation of SPAST and ATL1gene, multiplex ligation-dependent probe amplification （MLPA） platform for rearrangement mutation.2、To investigate the micromutation and rearrangement mutation frequeneies of SPAST and ATL1gene in HSP patients in China.Methods:We selected17AD-HSP and18sporadic HSP patients. Firstly, we detected the micro-mutations of ATL1with PCR and direct sequencing in17AD-HSP and18sporadic HSP patients in China; then detected rearrangement mutations of SPAST and ATL1with MLPA in17AD-HSP patients in China.Results:We found two micro-mutation c.1466₁467insTG and c.1242C>G; three SNPs84A>G、c.351G>A and c.1635A>G in ATL1gene. And two rearrangement mutations del. ex.13-15and del. ex.10-16in SPAST. No rearrangement mutation was founed in ATL1.Conclusion:First, we established MLPA technique platform for the rearrangement mutation in SPAST and ATL1.Second, in our study, rearrangement mutations in SPAST are responsible for11.8%of AD-HSP patients.Third, in our study, micro-mutation frequency of ATL1gene is5.7%. No rearrangement mutation was found in ATL1gene.