RESUMEN
Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disease caused by X-linked inherited mutations in the DYSTROPHIN (DMD) gene. Absence of dystrophin protein from the sarcolemma causes severe muscle degeneration, fibrosis, and inflammation, ultimately leading to cardiorespiratory failure and premature death. Although there are several promising strategies under investigation to restore dystrophin protein expression, there is currently no cure for DMD, and identification of genetic modifiers as potential targets represents an alternative therapeutic strategy. In a Brazilian golden retriever muscular dystrophy (GRMD) dog colony, two related dogs demonstrated strikingly mild dystrophic phenotypes compared with those typically observed in severely affected GRMD dogs despite lacking dystrophin. Microarray analysis of these "escaper" dogs revealed reduced expression of phosphatidylinositol transfer protein-α (PITPNA) in escaper versus severely affected GRMD dogs. Based on these findings, we decided to pursue investigation of modulation of PITPNA expression on dystrophic pathology in GRMD dogs, dystrophin-deficient sapje zebrafish, and human DMD myogenic cells. In GRMD dogs, decreased expression of Pitpna was associated with increased phosphorylated Akt (pAkt) expression and decreased PTEN levels. PITPNA knockdown by injection of morpholino oligonucleotides in sapje zebrafish also increased pAkt, rescued the abnormal muscle phenotype, and improved long-term sapje mutant survival. In DMD myotubes, PITPNA knockdown by lentiviral shRNA increased pAkt and increased myoblast fusion index. Overall, our findings suggest PIPTNA as a disease modifier that accords benefits to the abnormal signaling, morphology, and function of dystrophic skeletal muscle, and may be a target for DMD and related neuromuscular diseases.
Asunto(s)
Distrofia Muscular de Duchenne/metabolismo , Proteínas de Transferencia de Fosfolípidos/metabolismo , Proteínas de Transferencia de Fosfolípidos/fisiología , Animales , Línea Celular , Modelos Animales de Enfermedad , Perros , Distrofina/genética , Distrofina/metabolismo , Humanos , Células Musculares/fisiología , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/metabolismo , Distrofia Muscular Animal/genética , Distrofia Muscular de Duchenne/fisiopatología , Mutación , Fosforilación , Proteínas Proto-Oncogénicas c-akt , Pez Cebra/metabolismoRESUMEN
Duchenne muscular dystrophy (DMD), caused by mutations at the dystrophin gene, is the most common form of muscular dystrophy. There is no cure for DMD and current therapeutic approaches to restore dystrophin expression are only partially effective. The absence of dystrophin in muscle results in dysregulation of signaling pathways, which could be targets for disease therapy and drug discovery. Previously, we identified two exceptional Golden Retriever muscular dystrophy (GRMD) dogs that are mildly affected, have functional muscle, and normal lifespan despite the complete absence of dystrophin. Now, our data on linkage, whole-genome sequencing, and transcriptome analyses of these dogs compared to severely affected GRMD and control animals reveals that increased expression of Jagged1 gene, a known regulator of the Notch signaling pathway, is a hallmark of the mild phenotype. Functional analyses demonstrate that Jagged1 overexpression ameliorates the dystrophic phenotype, suggesting that Jagged1 may represent a target for DMD therapy in a dystrophin-independent manner. PAPERCLIP.
Asunto(s)
Proteínas de Unión al Calcio/genética , Modelos Animales de Enfermedad , Péptidos y Proteínas de Señalización Intercelular/genética , Proteínas de la Membrana/genética , Distrofia Muscular de Duchenne/genética , Animales , Proliferación Celular , Enfermedades de los Perros/genética , Perros , Distrofina/deficiencia , Distrofina/genética , Femenino , Estudio de Asociación del Genoma Completo , Proteína Jagged-1 , Masculino , Ratones , Distrofia Muscular Animal/genética , Linaje , Penetrancia , Proteínas Serrate-Jagged , Transcriptoma , Pez Cebra , Proteínas de Pez CebraRESUMEN
Facioscapulohumeral muscular dystrophy (FSHD) is a progressive muscle disorder that has been associated with a contraction of 3.3-kb repeats on chromosome 4q35. FSHD is characterized by a wide clinical inter- and intrafamilial variability, ranging from wheelchair-bound patients to asymptomatic carriers. Our study is unique in comparing the gene expression profiles from related affected, asymptomatic carrier, and control individuals. Our results suggest that the expression of genes on chromosome 4q is altered in affected and asymptomatic individuals. Remarkably, the changes seen in asymptomatic samples are largely in products of genes encoding several chemokines, whereas the changes seen in affected samples are largely in genes governing the synthesis of GPI-linked proteins and histone acetylation. Besides this, the affected patient and related asymptomatic carrier share the 4qA161 haplotype. Thus, these polymorphisms by themselves do not explain the pathogenicity of the contracted allele. Interestingly, our results also suggest that the miRNAs might mediate the regulatory network in FSHD. Together, our results support the previous evidence that FSHD may be caused by transcriptional dysregulation of multiple genes, in cis and in trans, and suggest some factors potentially important for FSHD pathogenesis. The study of the gene expression profiles from asymptomatic carriers and related affected patients is a unique approach to try to enhance our understanding of the missing link between the contraction in D4Z4 repeats and muscle disease, while minimizing the effects of differences resulting from genetic background.