RESUMO
Spinal muscular atrophy (SMA), which results from the loss of expression of the survival of motor neuron-1 (SMN1) gene, represents the most common genetic cause of pediatric mortality. A duplicate copy (SMN2) is inefficiently spliced, producing a truncated and unstable protein. We describe herein a potent, orally active, small-molecule enhancer of SMN2 splicing that elevates full-length SMN protein and extends survival in a severe SMA mouse model. We demonstrate that the molecular mechanism of action is via stabilization of the transient double-strand RNA structure formed by the SMN2 pre-mRNA and U1 small nuclear ribonucleic protein (snRNP) complex. The binding affinity of U1 snRNP to the 5' splice site is increased in a sequence-selective manner, discrete from constitutive recognition. This new mechanism demonstrates the feasibility of small molecule-mediated, sequence-selective splice modulation and the potential for leveraging this strategy in other splicing diseases.
Assuntos
Processamento Alternativo , Atrofia Muscular Espinal/tratamento farmacológico , RNA de Cadeia Dupla/agonistas , Ribonucleoproteína Nuclear Pequena U1/agonistas , Bibliotecas de Moléculas Pequenas/farmacologia , Proteína 2 de Sobrevivência do Neurônio Motor/metabolismo , Animais , Sítios de Ligação , Modelos Animais de Doenças , Feminino , Expressão Gênica , Humanos , Camundongos , Camundongos Transgênicos , Modelos Moleculares , Atrofia Muscular Espinal/metabolismo , Atrofia Muscular Espinal/mortalidade , Atrofia Muscular Espinal/patologia , Ligação Proteica/efeitos dos fármacos , Estabilidade Proteica/efeitos dos fármacos , Proteólise , Precursores de RNA/agonistas , Precursores de RNA/química , Precursores de RNA/metabolismo , RNA de Cadeia Dupla/química , RNA de Cadeia Dupla/metabolismo , Ribonucleoproteína Nuclear Pequena U1/química , Ribonucleoproteína Nuclear Pequena U1/metabolismo , Bibliotecas de Moléculas Pequenas/síntese química , Bibliotecas de Moléculas Pequenas/metabolismo , Análise de Sobrevida , Proteína 2 de Sobrevivência do Neurônio Motor/química , Proteína 2 de Sobrevivência do Neurônio Motor/genéticaRESUMO
Rett syndrome, a pervasive X-linked neurodevelopmental disorder in young girls, is caused by loss-of-function mutations in the gene that encodes the transcriptional repressor methyl-CpG-binding protein 2 (MeCP2). Mecp2-knockout mice phenocopy the major symptoms found in human patients and have advanced our understanding of the function of MeCP2 and mechanism of Rett syndrome. To study the behavior of the MeCP2 protein in vivo, we have generated a knock-in reporter mouse model that expresses MeCP2-enhanced green fluorescent protein (EGFP) fusion protein instead of endogenous MeCP2. Here we show that expression of the fusion protein in the brain remarkably mirrors endogenous MeCP2 expression in all temporal and spatial aspects. This mouse model may be a valuable tool for studying Rett syndrome and for developing therapies.
