The objective of this project is to develop a new approach that can be applied, in the long term, to therapeutic intervention in spinal muscular atrophy (SMA). SMA is an autosomal-recessive, pediatric neuromuscular disorder, characterized by the degeneration of spinal motor neurons. The protein encoded by the SMA-determining gene SMN1 is necessary for the survival of motor neurons. This gene is defective or absent in SMA patients, and its mouse homolog is essential for embryonic development. In humans, a second, nearly identical gene, SMN2, allows affected individuals to survive, but in most patients it cannot express sufficient amounts of active protein to fully compensate for the absence of SMN1. Splicing of the SMN2 pre-mRNA is predominantly via skipping of exon 7, whereas this exon is constitutively included in spliced SMN1 mRNA. Only the small fraction of correctly spliced SMN2 mRNA encodes functional SMN protein. A single-nucleotide difference between the two genes at position 6 of exon 7 - in synonymous codons - is responsible for the difference in splicing patterns. Increasing the extent of exon inclusion in the SMN2 transcripts should generate higher levels of functional protein, and is therefore expected to have therapeutic value. An SF2/ASF-dependent exonic splicing enhancer in exon 7 appears to be defective in SMN2, and recognition of this exon is very sensitive to subtle perturbations. Novel, small antisense molecules will be developed to promote exon 7 inclusion during SMN2 pre-mRNA splicing. The rational design of these molecules is based on recent advances in studies of pre-mRNA splicing factors and signals involved in exon definition. The new compounds will be tested and optimized using in vitro splicing of SMN2 pre-Mrna, and delivered into cultured cells. The best compounds will be tested for therapeutic effects, and will be further optimized, by delivering them systemically and locally into mice. These experiments will make use of the recently-developed mouse Smn knockout strain, rescued by a human SMN2 transgene, which is a useful animal model of SMA.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS041621-02
Application #
6540449
Study Section
Special Emphasis Panel (ZNS1-SRB-R (01))
Program Officer
Leblanc, Gabrielle G
Project Start
2001-06-01
Project End
2006-05-31
Budget Start
2002-06-01
Budget End
2003-05-31
Support Year
2
Fiscal Year
2002
Total Cost
$408,400
Indirect Cost
Name
Cold Spring Harbor Laboratory
Department
Type
DUNS #
065968786
City
Cold Spring Harbor
State
NY
Country
United States
Zip Code
11724
Hua, Yimin; Vickers, Timothy A; Baker, Brenda F et al. (2007) Enhancement of SMN2 exon 7 inclusion by antisense oligonucleotides targeting the exon. PLoS Biol 5:e73
Cartegni, Luca; Hastings, Michelle L; Calarco, John A et al. (2006) Determinants of exon 7 splicing in the spinal muscular atrophy genes, SMN1 and SMN2. Am J Hum Genet 78:63-77