Analysis of deletions in SMN1, SMN2, and NAIP genes in spinal muscular atrophy patients from the northwestern region of Russia

Polymerase chain reaction with subsequent SSCP (single-strand DNA conformat ional polymorphism) and restriction (BselI restriction endonuclease) analys es were used to type the DNA samples or affected individuals and their rela tives from 23 Russian families with high risk of spinal muscular atrophy (S MA) residing in the northwestern region of Russia. Deletions of exon 7 of t he SMN1 gene were found in 96% of the individuals examined. The frequency o f homozygous deletion of exons 7 and 8 of the SMN1 gene was 65%, The freque ncy of homozygous isolated deletion of the SMN1 gene exon 7 among the SMA p atients was 4.3%. Homozygous deletion of exon 5 of the NAIP gene was found in 22% of SMA patients. In SMA patients, a total of seven deletion types in volving the SMN1, NAIP, and SMN2 genes were detected. Deletion of exons 7 a nd 8 of the SMN1 gene was the most common mutation associated with SMA in p atients from the northwestern Russia.