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Disrupted prenatal RNA processing and myogenesis in congenital myotonic dystrophy.

ABSTRACT: Myotonic dystrophy type 1 (DM1) is a CTG microsatellite expansion (CTG^exp) disorder caused by expression of CUG^exp RNAs. These mutant RNAs alter the activities of RNA processing factors, including MBNL proteins, leading to re-expression of fetal isoforms in adult tissues and DM1 pathology. While this pathogenesis model accounts for adult-onset disease, the molecular basis of congenital DM (CDM) is unknown. Here, we test the hypothesis that disruption of developmentally regulated RNA alternative processing pathways contributes to CDM disease. We identify prominent alternative splicing and polyadenylation abnormalities in infant CDM muscle, and, although most are also misregulated in adult-onset DM1, dysregulation is significantly more severe in CDM. Furthermore, analysis of alternative splicing during human myogenesis reveals that CDM-relevant exons undergo prenatal RNA isoform transitions and are predicted to be disrupted by CUG^exp-associated mechanisms in utero. To test this possibility and the contribution of MBNLs to CDM pathogenesis, we generated mouse Mbnl double (Mbnl1; Mbnl2) and triple (Mbnl1; Mbnl2; Mbnl3) muscle-specific knockout models that recapitulate the congenital myopathy, gene expression, and spliceopathy defects characteristic of CDM. This study demonstrates that RNA misprocessing is a major pathogenic factor in CDM and provides novel mouse models to further examine roles for cotranscriptional/post-transcriptional gene regulation during development.

SUBMITTER: Thomas JD

PROVIDER: S-EPMC5538435 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Disrupted prenatal RNA processing and myogenesis in congenital myotonic dystrophy.

Thomas James D JD Sznajder Łukasz J ŁJ Bardhi Olgert O Aslam Faaiq N FN Anastasiadis Zacharias P ZP Scotti Marina M MM Nishino Ichizo I Nakamori Masayuki M Wang Eric T ET Swanson Maurice S MS

Genes & development 20170601 11

Myotonic dystrophy type 1 (DM1) is a CTG microsatellite expansion (CTG<sup>exp</sup>) disorder caused by expression of CUG<sup>exp</sup> RNAs. These mutant RNAs alter the activities of RNA processing factors, including MBNL proteins, leading to re-expression of fetal isoforms in adult tissues and DM1 pathology. While this pathogenesis model accounts for adult-onset disease, the molecular basis of congenital DM (CDM) is unknown. Here, we test the hypothesis that disruption of developmentally regu ...[more]

PMID: 28698297

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Project description:Myotonic dystrophy type 1 (DM1) and 2 (DM2) are autosomal dominant degenerative neuromuscular disorders characterized by progressive skeletal muscle weakness, atrophy, and myotonia with progeroid features. Although both DM1 and DM2 are characterized by skeletal muscle dysfunction and also share other clinical features, the diseases differ in the muscle groups that are affected. In DM1, distal muscles are mainly affected, whereas in DM2 problems are mostly found in proximal muscles. In addition, manifestation in DM1 is generally more severe, with possible congenital or childhood-onset of disease and prominent CNS involvement. DM1 and DM2 are caused by expansion of (CTG•CAG)n and (CCTG•CAGG)n repeats in the 3' non-coding region of DMPK and in intron 1 of CNBP, respectively, and in overlapping antisense genes. This critical review will focus on the pleiotropic problems that occur during development, growth, regeneration, and aging of skeletal muscle in patients who inherited these expansions. The current best-accepted idea is that most muscle symptoms can be explained by pathomechanistic effects of repeat expansion on RNA-mediated pathways. However, aberrations in DNA replication and transcription of the DM loci or in protein translation and proteome homeostasis could also affect the control of proliferation and differentiation of muscle progenitor cells or the maintenance and physiological integrity of muscle fibers during a patient's lifetime. Here, we will discuss these molecular and cellular processes and summarize current knowledge about the role of embryonic and adult muscle-resident stem cells in growth, homeostasis, regeneration, and premature aging of healthy and diseased muscle tissue. Of particular interest is that also progenitor cells from extramuscular sources, such as pericytes and mesoangioblasts, can participate in myogenic differentiation. We will examine the potential of all these types of cells in the application of regenerative medicine for muscular dystrophies and evaluate new possibilities for their use in future therapy of DM.

Project description:Abstract BACKGROUND: Congenital Myotonic Dystrophy (CDM) is the harshest form of Myotonic Dystrophy type 1 (DM1,OMIM #160900). The mode of inheritance is autosomal dominant, and results from a microsatellite expansion in DMPK with an incidence of 2.1:1000,000 live births in Canada. The principal clinical signs during the neonatal period are myopathic facies, hypotonia and weakness resulting in such features as talipes equinovarus, nutritional, cardiac and respiratory problems. OBJECTIVES: To describe the main findings of CDM in the perinatal period. DESIGN/METHODS: A five year prospective cohort study from 2005 to 2010 of eligible incident cases of CDM was performed via the Canadian Pediatric Surveillance Program (CPSP). Reporting physicians completed a questionnaire with the medical history at birth and during the perinatal period. Our patients met the CDM criteria proposed by Campbell et al. (2013): 1) CDM symptoms with hospitalization greater of 72 hours; and 2) CTGrs above 200. RESULTS: We obtained 43 questionnaires, 22 female and 21 male (F:M ratio of 1.04:1). Average CTG repeat size (CGTrs) was 795.67 (250-2300). The main complication during the prenatal period was polyhydramnios (n=20). The majority of the patients (n=27) had full term pregnancy and with normal birth weight (n=25). Average Apgar was 4 at 1 (range 1-9), and 6 for 5 and 10. Intubation was required in 29/43 of the cases, with an average hospital stay of 43.5 days. Nutritional support (ie ng feeds) was required in 34/43, and it was longer than 14 days in 21 patients. Nine patients died, 6 of them due to respiratory failure. Four deaths were withdrawal of life support. CONCLUSION: The respiratory difficulties are well described as the principal complication in CDM (Ho et al. [2015]), but we found that the necessity of multiple nutritional interventions was the most frequent neonatal complication (79%), respiratory complications remains as the principal cause of death (66.6%). Zaki et al. (2010) describes a cohort with a 100% frequency of polyhydramnios, differing on ours where it is 46.5%. We conclude that CDM is not always evident prenatally by polyhydramnios, IUGR or preterm delivery. Nutritional and respiratory assessments should be prioritized, and nutritional interventions may extend for long periods of time. Despite high respiratory and feeding support needs, the majority of patients improved over time. Hence the importance of prenatal counseling and preparation for the complications in the neonatal period.

Dataset Information

Disrupted prenatal RNA processing and myogenesis in congenital myotonic dystrophy.

Publications

Disrupted prenatal RNA processing and myogenesis in congenital myotonic dystrophy.

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