To define numerically the clinical severity of facioscapulohumeral muscular dystrophy (FSHD), we developed a protocol that quantifies muscle weakness by combining the functional evaluation of six muscle groups affected in this disease. To validate reproducibility of the protocol, 69 patients were recruited. Each patient was evaluated by at least five neurologists, and an FSHD severity score was given by each examiner. The degree of agreement among clinicians' evaluations was measured by kappa-statistics. Nineteen subjects received a score between 0 and 1, 9 had a score between 2 and 4, 20 received a score between 5 and 10, and 8 had a score between 11 and 15. Of the 13 subjects with D4Z4 alleles within the normal range (ranging from 10 to 150 repeats), 12 obtained a score of 0 and only 1 had a score of 1. Kappa-statistics showed a very high concordance for all muscle groups. We developed a simple, reliable, easily used tool to define the clinical expression of FSHD. Longitudinal studies will assess its sensitivity and utility in measuring changes for widespread use.

The objective of this study was to determine the degree of brain involvement in a cohort of myotonic dystrophy type 1 and type 2 (DM1, DM2) patients by brain studies and functional tests and to compare the results of the two groups. DM1, DM2 are multisystemic disorders due to polynucleotide expansions. Previous studies on brain involvement by neuroimaging and functional methods have led to contradictory results. Fifty molecularly defined DM1 patients and 14 DM2 patients, were recruited for the study. Age at recruitment, age at disease onset, disease duration and educational level were recorded. Neuromuscular assessment was done by MIRS. An extensive neuropsychological battery was performed in 48/50 DM1 and in a control group of 44 healthy matched subjects. Forty six of 50 DM1 and 12/14 DM2 underwent brain MRI; 21/50 DM1 and 9/14 DM2 underwent brain perfusion SPECT, with semiquantitative analysis of the results. MRI images were classified by ARWMC (age-related white matter changes) score, in order to quantify recurrence, localization and patterns of distribution of white matter hyperintense lesions (WMHLs) in our two cohorts. MRI results were matched to SPECT and to neuropsychological results. Thirty-seven of 46 DM1 and 10/12 DM2 had abnormal MRI imaging, showing scattered supratentorial, bilateral, symmetrical focal or diffuse WMHLs. A typical temporo-insular diffuse subcortical pattern was seen in DM1 subjects only, with no correlation with cognitive involvement. Major cognitive involvement was seen in the case of diffuse frontal lesions. A relationship with CTG expansion size was documented for DM1 subjects. SPECT showed minimal hypoperfusion in the posterior cortex planes in DM1 and, to a lesser extent, in DM2. Very mild degrees of involvement in the DM2 cohort were seen. Neuroimaging and functional investigations confirmed a more severe involvement of the brain in DM1 compared to DM2. A temporo-insular diffuse lesional pattern, specific for DM1, was found on MRI. This confirms greater expansion size as a risk factor for more extensive brain involvement in DM1.

The CTG repeat length plays a key role in the extent of splicing misregulation and foci formation, thus providing a useful link between the genotype and the molecular cellular phenotype in DM1.

Myotonic dystrophy is caused by two different mutations: a (CTG)n expansion in 3' UTR region of the DMPK gene (DM1) and a (CCTG)n expansion in intron 1 of the ZNF9 gene (DM2). The most accredited mechanism for DM pathogenesis is an RNA gain-of-function. Other findings suggest a contributory role of DMPK-insufficiency in DM1. To address the issue of ZNF9 role in DM2, we have analyzed the effects of (CCTG)n expansion on ZNF9 expression in lymphoblastoid cell lines (n=4) from DM2 patients. We did not observe any significant alteration in ZNF9 mRNA and protein levels, as shown by QRT-PCR and Western blot analyses. Additional RT-PCR experiments demonstrated that ZNF9 pre-mRNA splicing pattern, which includes two isoforms, is unmodified in DM2 cells. Our results indicate that the (CCTG)n expansion in the ZNF9 intron does not appear to have a direct consequence on the expression of the gene itself.

Myotonic dystrophy type 1 (DM1) is a multisystem disorder that affects skeletal and smooth muscle as well as the eye, heart, endocrine system, and central nervous system. DM1 is caused by expansion of a CTG trinucleotidedaggerrepeat in the gene DMPK. Clinical findings in DM1 span a continuum from mild to severe. Although the CTG repeat correlates with the disease phenotype, caution is used in predicting disease severity on the basis of CTG repeat number. This study reports an extensive genotype-phenotype study to evaluate the clinical validity and clinical utility of the molecular genetic test. Data were analyzed by multiple logistic regression, used to estimate the odds ratio (OR) and correlation coefficients for patients phenotype in respect to the categorical variables expansion class, gender, familiarity, and the continuous variables age and disease duration. We assessed disease expression by clinical evaluation and the molecular genetic test in 2,650 patients identified by accurate clinical diagnosis and family segregation. We were able to estimate OR and correlation coefficients for patients phenotype according to CTG number. A genotype-phenotype correlation was established to derivate a clinical predictive risk on the basis of molecular data. This study demonstrates that measurement of triplet expansions in patients' DNA can be considered as a useful tool for DM1 phenotype assessment and presymptomatic testing.