[PDF][PDF] Antisense masking of an hnRNP A1/A2 intronic splicing silencer corrects SMN2 splicing in transgenic mice

Y Hua, TA Vickers, HL Okunola, CF Bennett… - The American Journal of …, 2008 - cell.com
Y Hua, TA Vickers, HL Okunola, CF Bennett, AR Krainer
The American Journal of Human Genetics, 2008cell.com
survival of motor neuron 2, centromeric (SMN2) is a gene that modifies the severity of spinal
muscular atrophy (SMA), a motor-neuron disease that is the leading genetic cause of infant
mortality. Increasing inclusion of SMN2 exon 7, which is predominantly skipped, holds
promise to treat or possibly cure SMA; one practical strategy is the disruption of splicing
silencers that impair exon 7 recognition. By using an antisense oligonucleotide (ASO)-tiling
method, we systematically screened the proximal intronic regions flanking exon 7 and …
survival of motor neuron 2, centromeric (SMN2) is a gene that modifies the severity of spinal muscular atrophy (SMA), a motor-neuron disease that is the leading genetic cause of infant mortality. Increasing inclusion of SMN2 exon 7, which is predominantly skipped, holds promise to treat or possibly cure SMA; one practical strategy is the disruption of splicing silencers that impair exon 7 recognition. By using an antisense oligonucleotide (ASO)-tiling method, we systematically screened the proximal intronic regions flanking exon 7 and identified two intronic splicing silencers (ISSs): one in intron 6 and a recently described one in intron 7. We analyzed the intron 7 ISS by mutagenesis, coupled with splicing assays, RNA-affinity chromatography, and protein overexpression, and found two tandem hnRNP A1/A2 motifs within the ISS that are responsible for its inhibitory character. Mutations in these two motifs, or ASOs that block them, promote very efficient exon 7 inclusion. We screened 31 ASOs in this region and selected two optimal ones to test in human SMN2 transgenic mice. Both ASOs strongly increased hSMN2 exon 7 inclusion in the liver and kidney of the transgenic animals. Our results show that the high-resolution ASO-tiling approach can identify cis-elements that modulate splicing positively or negatively. Most importantly, our results highlight the therapeutic potential of some of these ASOs in the context of SMA.
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