title: Improvement of SMN2 pre-mRNA processing mediated by exon-specific U1 small nuclear RNA.
abstract: Exon-specific U1 snRNAs (ExSpe U1s) are modified U1 snRNAs that interact with intronic sequences downstream of the 5' splice site (ss) by complementarity. This process restores exon skipping caused by different types of mutation. We have investigated the molecular mechanism and activity of these molecules in spinal muscular atrophy (SMA), a genetic neuromuscular disease where a silent exonic transition on the survival motor neuron 2 (SMN2) leads to exon 7 (E7) skipping. By using different cellular models, we show that a single chromosome-integrated copy of ExSpe U1 induced a significant correction of endogenous SMN2 E7 splicing and resulted in the restoration of the corresponding SMN protein levels. Interestingly, the analysis of pre-mRNA transcript abundance and decay showed that ExSpe U1s promote E7 inclusion and stabilizes the SMN pre-mRNA intermediate. This selective effect on pre-mRNA stability resulted in higher levels of SMN mRNAs in comparison with those after treatment with an antisense oligonucleotide (AON) that targets corresponding intronic sequences. In mice harboring the SMN2 transgene, AAV-mediated delivery of ExSpe U1 increased E7 inclusion in brain, heart, liver, kidney, and skeletal muscle. The positive effect of ExSpe U1s on SMN pre-mRNA processing highlights their therapeutic potential in SMA and in other pathologies caused by exon-skipping mutations.
authors.affiliation: Human Molecular Genetics Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano 99, 34149 Trieste, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Dal Mas
authors.affiliation: Human Molecular Genetics Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano 99, 34149 Trieste, Italy.
authors.forename: Malgorzata Ewa
authors.initials: ME
authors.lastname: Rogalska
authors.affiliation: Human Molecular Genetics Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano 99, 34149 Trieste, Italy.
authors.forename: Erica
authors.initials: E
authors.lastname: Bussani
authors.affiliation: Human Molecular Genetics Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano 99, 34149 Trieste, Italy. Electronic address: pagani@icgeb.org.
authors.forename: Franco
authors.initials: F
authors.lastname: Pagani
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005091:Exons; D005260:Female; D056426:Genetic Loci; D057809:HEK293 Cells; D006801:Humans; D007438:Introns; D016086:Lentivirus / Q000235:genetics; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009134:Muscular Atrophy, Spinal / Q000235:genetics; D009690:Nucleic Acid Conformation; D012322:RNA Precursors / Q000235:genetics*; D022821:RNA Splice Sites; D012326:RNA Splicing; D012342:RNA, Small Nuclear / Q000235:genetics* / Q000378:metabolism; D055540:Survival of Motor Neuron 2 Protein / Q000235:genetics* / Q000378:metabolism; D014161:Transduction, Genetic
chemical_list: D012322:RNA Precursors; D022821:RNA Splice Sites; D012342:RNA, Small Nuclear; D055540:Survival of Motor Neuron 2 Protein; C405483:U1 small nuclear RNA