The underlying mechanism
responsible for muscle weakness and wasting remains to be established. Recent findings suggest that DM mutations can affect gene expression in multiple ways. Altered activity and/or localization of MBNL1 and CELF1 may alter transcription, translation and cell signaling (68, 69). Moreover it has been demonstrated that in DM1 the highly regulated pathways of miRNA is altered in skeletal muscle and heart tissue potentially contributing to DM1 pathogenetic mechanisms and in DM2 skeletal Inhibitors,research,lifescience,medical muscle (70-73). Another open question in the field of DM is to clarify the pathomecanisms underlying the phenotypic click here differences between DM1 and DM2. Clinical signs in DM1 and DM2 are similar, Inhibitors,research,lifescience,medical but there are some distinguishing features: DM2 is generally
less severe and lacks a prevalent congenital form. This suggests that other cellular and molecular pathways are involved besides the shared toxic-RNA gain of function hypothesized. Disease-specific manifestations may result from differences in spatial and Inhibitors,research,lifescience,medical temporal expression patterns of DMPK and CNBP genes. Similarly, changes in the expression of neighbouring genes may define diseasespecific manifestations. Importantly, the role of CELF1 in DM2 is particularly intriguing with contradictory results being reported (54, 59, 62). Another possible explanation for the clinical differences between the two DM forms is the reduction of DMPK or ZNF9 protein levels in DM1 and DM2 respectively (3, 74-76). Indeed both knockout mouse models for DMPK and ZNF9 show the phenotypic aspects Inhibitors,research,lifescience,medical of DM (77, 78). Taken together these observations seem indicate that the emerging pathways of molecular pathogenesis are far more complex than previously appreciated. Diagnostics Inhibitors,research,lifescience,medical Laboratory tests As for all genetics diseases with identified mutation, the typical DM1 and DM2 diagnostic method is mutation verification by genetic tests. In the case of DM1, symptoms and family history are often clear and distinctive enough to make a clinical diagnosis, and the mutation
can be confirmed by PCR and Southern Blot analysis. PCR analysis is used to detect repeat lengths less than 100 and Southern blot analysis to detect larger expansions. Predictive testing in asymptomatic relatives as well as prenatal and preimplantation diagnosis can also be old performed. On the contrary, the wide clinical spectrum of DM2 phenotype makes the clinical diagnosis more difficult. Moreover conventional PCR and Southern blot analysis are not adequate for a definitive molecular diagnosis in DM2 due to the extremely large size and somatic instability of the expansion mutation (9, 46). The copy number of DM2 CCTG is below 30 in phenotypically normal individuals and up 11.000 in patients (79).