Correction of GSK3ß at young age prevents muscle pathology in mice with myotonic dystrophy type 1.

Myotonic dystrophy type 1 (DM1) is a progressive neuromuscular disease caused by expanded CUG repeats, which misregulate RNA metabolism through several RNA-binding proteins, including CUG-binding protein/CUGBP1 elav-like factor 1 (CUGBP1/CELF1) and muscleblind 1 protein. Mutant CUG repeats elevate CUGBP1 and alter CUGBP1 activity via a glycogen synthase kinase 3ß (GSK3ß)-cyclin D3-cyclin D-dependent kinase 4 (CDK4) signaling pathway. Inhibition of GSK3ß corrects abnormal activity of CUGBP1 in DM1 mice [human skeletal actin mRNA, containing long repeats ( HSALR) model]. Here, we show that the inhibition of GSK3ß in young HSALR mice prevents development of DM1 muscle pathology. Skeletal muscle in 1-yr-old HSALR mice, treated at 1.5 mo for 6 wk with the inhibitors of GSK3, exhibits high fiber density, corrected atrophy, normal fiber size, with reduced central nuclei and normalized grip strength. Because CUG-GSK3ß-cyclin D3-CDK4 converts the active form of CUGBP1 into a form of translational repressor, we examined the contribution of CUGBP1 in myogenesis using Celf1 knockout mice. We found that a loss of CUGBP1 disrupts myogenesis, affecting genes that regulate differentiation and the extracellular matrix. Proteins of those pathways are also misregulated in young HSALR mice and in muscle biopsies of patients with congenital DM1. These findings suggest that the correction of GSK3ß-CUGBP1 pathway in young HSALR mice might have a positive effect on the myogenesis over time.-Wei, C., Stock, L., Valanejad, L., Zalewski, Z. A., Karns, R., Puymirat, J., Nelson, D., Witte, D., Woodgett, J., Timchenko, N. A., Timchenko, L. Correction of GSK3ß at young age prevents muscle pathology in mice with myotonic dystrophy type 1.

Prevalence of lifestyle risk factors in myotonic dystrophy type 1.

BACKGROUND: The prevalence of unhealthy lifestyle habits such as smoking has seldom been described in neuromuscular disorders, including myotonic dystrophy type 1 (DM1). However, it is essential to document the unhealthy lifestyle habits as they can exacerbate existing impairments and disabilities. The objectives are: 1) To determine the prevalence of risk factors among individuals with DM1; 2) To compare the prevalence among classic and mild phenotypes. METHOD: A survey was done on a sample of two-hundred (200) patients with DM1 as part of a larger study. Lifestyle risk factors included being overweight or obese, tobacco smoking, illicit drug use, excessive alcohol consumption and physical inactivity. A registered nurse administered the validated public health survey. Categorization of risk factors were based on national standards and compared with provincial and regional prevalences. RESULTS: 50% of DM1 patients were overweight or obese, 23.6% were regular smokers, and 76% were physically inactive. Except for overweight and obesity, significant differences were observed between patients with classic and mild phenotypes for all the other lifestyle risk factors: those with the classic phenotype being more often regular smokers, consuming more often illicit drugs and being less physically active. CONCLUSIONS: The results of this study will provide guidance for the development of better adapted and focussed health promotion interventions in the future.

[Genetic diagnosis of IVF embryos: preliminary results from 'preimplantation genetic diagnoses' in the Netherlands]. / Genetische diagnostiek bij IVF-embryo's: eerste ervaringen met 'preïmplantatiegenetische diagnostiek' in Nederland.

Preimplantation genetic diagnosis (PGD) is a very early form of genetic testing. It involves testing one or two cells taken from a recent embryo of eight cells produced by in vitro fertilization, and selective transfer of genetically normal embryos. So far in the Academic Hospital Maastricht, the Netherlands, 20 couples have undergone PGD, resulting in 6 ongoing pregnancies (one twin pregnancy). In three women the indications for PGD were: cystic fibrosis, sex-linked Pelizaeus-Merzbacher disease and chromosomal translocation, respectively. In the Netherlands PGD is only allowed if there is a high risk of a serious genetic disease. PGD can be carried out in Maastricht for: cystic fibrosis, sex-linked diseases, chromosomal abnormalities, fragile X syndrome, spinal muscular atrophy and myotonic dystrophy. The advantage of PGD is that it excludes the necessity of a therapeutic abortion. Disadvantages ages are the requirement of in vitro fertilization, which has only a 15-20% pregnancy rate, and the experimental nature of the PGD procedure. To date, about 200 children have been born worldwide following PGD.

Single-cell analysis of unstable genes.

PURPOSE: We have developed sensitive diagnostic procedures for studies on the normal and mutant alleles of the triplet repeat genes associated with myotonic dystrophy and fragile X in single human somatic cells, gametes and embryos. METHODS: Polymerase chain reaction (PCR) assays for the normal alleles of the myotonic dystrophy and fragile X loci have been refined to the sensitivity of the single cell. In addition, we have developed a simple PCR-based technique, termed ¿Repeat Primer PCR', which can detect the full fragile X expansion in small samples of buccal cells. CONCLUSIONS: The assay for the triplet repeat sequence in the myotonic dystrophy locus could not be used to study stability since we observed additional PCR products derived from in vitro expansion of the triplet repeat sequence during the PCR reaction itself. The implications of in vitro expansion and allele drop-out for studies on the timing of the expansion in development and preimplantation diagnosis of triplet repeat diseases are discussed. The development of a new PCR procedure to identify the expanded alleles of the fragile X locus could prove invaluable for monitoring the timing of repeat expansion in early embryonic development. Triplet repeat polymorphisms provide a means of identifying the maternally and paternally-derived alleles of the myotonic dystrophy gene. Using single cell reverse transcriptase PCR analysis, we have monitored the onset of the myotonic dystrophy gene transcription in early preimplantation embryos. Transcripts from the paternally-inherited allele of the myotonic dystrophy gene are already detectable in the 1-cell stage human embryo.

Direct molecular analysis of myotonic dystrophy in the German population: important considerations in genetic counselling.

Myotonic dystrophy (DM) is associated with the expansion and instability of a trinucleotide (CTG) repeat at the DM locus on chromosome 19. Direct genomic analysis in the German population was carried out on 18 DM families, six families with equivocal diagnosis, 69 subjects with equivocal clinical diagnosis, and 100 controls using the polymerase chain reaction (PCR) and a refined Southern protocol. In the majority of the cases molecular analysis confirmed the clinical diagnosis. These included seven cases of congenital DM (CDM) with widely differing gene expansions and instabilities. In most DM families the expanded fragment became larger in successive generations, but we also identified four families with contractions and two families that showed stability of the enlarged fragment during transmission. In four clinically defined DM patients we were unable to detect enlarged CTG repeats. Sequencing of each exon of the DM gene in two of these patients failed to show any mutations. Our cases have important implications for genetic counselling of DM families, highlighting both the diagnostic value of direct genomic analysis and its limitations.

Cataract and myotonic dystrophy: the role of molecular diagnosis.

Myotonic dystrophy (dystrophia myotonica), the commonest and most variable of the muscular dystrophies of adult life, has long been known to be associated with cataract, while slit-lamp examination for specific lens opacities has been one of the principal methods of presymptomatic detection of gene carriers. The recent discovery that the myotonic dystrophy mutation is an unstable DNA sequence, composed of varying numbers of CTG triplet repeats, now allows a specific molecular test for this disorder, as well as explaining the phenomenon of anticipation. A series of case reports is presented to illustrate the important practical applications of this development in relation to ophthalmic aspects of the disorder. Reassessment of the specificity of the ophthalmic changes may be required and it will be important for molecular analysis to be used alongside ophthalmic studies, when determining whether family members carry the mutation for myotonic dystrophy.

Myotonic dystrophy: opportunities for prenatal prediction.

Prenatal prediction of the inheritance of myotonic dystrophy in a family with affected individuals feasible in special cases when analysis of linkage to the secretor gene (determing ABH substances) can be carried out. We report a large kindred having multiple members affected with variable degrees of severity of myotonic dystrophy and having several matings for which linkage analysis is feasible. Even though this approach is not applicable for most families and although the process of genetic recombination complicates the analysis, in individual cases the use of linkage in prenatal or postnatal prediction of myotonic dystrophy may be very helpful for early diagnosis, more precise genetic counseling, and family planning.