Objective To prepare the survival motor neuron(SMN)polyclonal antibody and explore the localization of SMN protein in transfected cells and its expression in skeletal muscles of patients with spinal muscular atrophy(SMA).Methods A prokaryotic expressional plasmid named pET-28? (+)/SMN was constructed and SMN-His fusion protein was induced.The fusion protein was used to immunize New Zealadd rabbits to prepare SMN polyclonal antibody.A eukaryotic expressional plasmid named pcDNA3.1/myc-HisB-SMN was constructed and used to transfect CHO cells.Skeletal muscles were collected from 3 patients with bone fracture who were regarded as normal controls, and 3 SMA patients of type Ⅰ, 3 of type Ⅱ and 3 of type Ⅲ who were ascertained by genetic analysis.Western-blotting and immunofluorescence stain were applied to study the expression of SMN in transfected CHO cells and skeletal muscles of normal individuals and SMA patients.Results Correct pET-28a(+)/SMN prokaryotic expressive plasmid was constructed and SMN-His fusion protein was obtained from E coli BL21 transformed with pET-28a(+)/SMN.Then, rabbit anti-human full-length SMN polyclonal antibody of high specificity and sensitivity was obtained from rabbits immunized by SMN-His fusion protein.SMN proteins were shown diffusedly locating in the cytoplasm and nucleus of CHO cells transfected with pcDNA3.1/myc-HisB-SMN plasmid and mainly accumulating around the nucleus.The results of Western-blotting were as follows:the average ratio of SMN band density to glyceraldehyde phosphate dehydrogenase(GAPDH)band density (SMN/GAPDH)is 0.619 in skeletal muscles from normal controls, the average values of SMN/GAPDH in skeletal muscle from SMA patients of type Ⅲ and Ⅱ were 0.347 and 0.340 respectively, which were lower than that of normal controls.However, the average values of SMN/GAPDH in skeletal muscle from SMA patients of type I was only 0.079, which was quite lower than that of normal controls.Conclusions The rabbit anti-human full-length SMN polyclonal antibody is of high specificity and sensitivity, which makes the basis for the research of SMN function and SMA pathogenesis.There may be a correlation between the SMN level in skeletal muscle and the severity of disease.