title: The benzamide M344, a novel histone deacetylase inhibitor, significantly increases SMN2 RNA/protein levels in spinal muscular atrophy cells.
abstract: Proximal spinal muscular atrophy (SMA) is a common autosomal recessively inherited neuromuscular disorder causing infant death in half of all patients. Homozygous loss of the survival motor neuron 1 (SMN1) gene causes SMA, whereas the number of the SMN2 copy genes modulates the severity of the disease. Due to a silent mutation within an exonic splicing enhancer, SMN2 mainly produces alternatively spliced transcripts lacking exon 7 and only approximately 10% of a full-length protein identical to SMN1. However, SMN2 represents a promising target for an SMA therapy. The correct splicing of SMN2 can be efficiently restored by over-expression of the splicing factor Htra2-beta1 as well as by exogenous factors like drugs that inhibit histone deacetylases (HDACs). Here we show that the novel benzamide M344, an HDAC inhibitor, up-regulates SMN2 protein expression in fibroblast cells derived from SMA patients up to 7-fold after 64 h of treatment. Moreover, M344 significantly raises the total number of gems/nucleus as well as the number of nuclei that contain gems. This is the strongest in vitro effect of a drug on the SMN protein level reported so far. The reversion of Delta7-SMN2 into FL-SMN2 transcripts as demonstrated by quantitative RT-PCR is most likely facilitated by elevated levels of Htra2-beta1. Investigations of the cytotoxicity of M344 using an MTT assay revealed toxic cell effects only at very high concentrations. In conclusion, M344 can be considered as highly potent HDAC inhibitor which is active at low doses and therefore represents a promising candidate for a causal therapy of SMA.
authors.affiliation: Institute of Human Genetics, Institute of Genetics, and Center for Molecular Medicine Cologne, University of Cologne, Kerpener Str. 34, 50931 Cologne, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Riessland
authors.forename: Lars
authors.initials: L
authors.lastname: Brichta
authors.forename: Eric
authors.initials: E
authors.lastname: Hahnen
authors.forename: Brunhilde
authors.initials: B
authors.lastname: Wirth
mesh_terms: D017398:Alternative Splicing; D015153:Blotting, Western; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005455:Fluorescent Antibody Technique; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D009134:Muscular Atrophy, Spinal / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D055532:SMN Complex Proteins; D055533:Survival of Motor Neuron 1 Protein; D055540:Survival of Motor Neuron 2 Protein; D014158:Transcription, Genetic / Q000187:drug effects; D000077337:Vorinostat
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; C526471:SMN1 protein, human; C526477:SMN2 protein, human; D055533:Survival of Motor Neuron 1 Protein; D055540:Survival of Motor Neuron 2 Protein; D000077337:Vorinostat