ABSTRACT
Mutations in one of the duplicated survival of motor neuron (SMN) genes lead to the progressive loss of motor neurons and subsequent development of spinal muscular atrophy (SMA), a common, and usually fatal, hereditary disease. Homozygous absence of the telomeric copy (SMN1) correlates with development of SMA because differential splicing of the centromeric copy (SMN2) leads to exon 7 skipping and predominantly produces a biologically inactive protein isoform. To increase exon 7 inclusion of SMN2, we have designed a series of vectors that express modified U7 snRNAs containing antisense sequences complementary to the 3' splice site of SMN exon 8. Over 20 anti-SMN U7 snRNAs were tested for their ability to promote exon 7 inclusion in the SMN2 gene. Transient expression of anti-SMN U7 snRNAs in HeLa cells modulated SMN2 splicing to approximately 70% exon 7 inclusion in a sequence-specific and dose-dependent manner. Significantly, the administration of anti-SMN U7 snRNPs results in an increase in the concentration of SMN protein. These results suggest that modulation of SMN2 pre-mRNA splicing by modified U7 snRNAs provides a promising form of gene therapy for the treatment of SMA.