464), localised in the SK3 intron 5, which abolishes a MboII enzyme restriction site. The PCR products containing the SNP region were, therefore, digested with the MboII enzyme: two DNA fragments of 226 and 177 bp were yielded for the C allele and only one band for the T allele (Fig. ​(Fig.2C).2C). The allelic and genotypic frequencies for the rs6656494 and rs10128027 SNPs observed in the AVB-DM1 and no AVB-DM1 patients are reported in Table ​Table2.2. The genotype

distribution for both SNPs, in our sample, is in agreement with the Hardy-Weinberg equilibrium. Chi-square analysis of the allelic Inhibitors,research,lifescience,medical distribution between the two groups (AVB-DM1 and no AVB-DM1) revealed the lack of association with the AVB phenotype for both rs6656494 and rs10128027 SNPs (Χ2 = 1.61, p < 1 and Χ2 = 0.14, p < 1, respectively). Figure 1 qRT-PCR quantification of SK3 transcript expression

levels in skeletal muscle from seven DM1 patients and two pooled Luminespib ic50 controls (CTR). The average result of Inhibitors,research,lifescience,medical normal Inhibitors,research,lifescience,medical controls was given a value of 1. Each experiment was performed in triplicate. Relative quantification … Table 2 Allelic and genotypic frequencies of SNPs rs6656494 and rs10128027 in the two groups of DM1 patients. AVB: DM1 patients with atrioventricular block; NoAVB: DM1 patients without atrioventricular block. We Inhibitors,research,lifescience,medical therefore investigated the possibility of an association between the number of [CTG]n repetitions in the DMPK gene and the presence of the

AVB phenotype in the present cohort of DM1 patients. Patients were stratified according to the three classes of expansion (E1:50-150 [CTG]n; E2: 150-1000 [CTG]n; E3: up to 1000 [CTG]n) currently applied Inhibitors,research,lifescience,medical for DM1 (1). Both groups showed a homogeneous distribution between the three classes (r = 0.918; Χ2 = 0.359, p = 8.36), thus excluding a direct correlation between the occurrence of AVB and the DMPK [CTG]n expansion. This result is in accordance with other previous studies (34, 35). Discussion and conclusions Over-expression of the SK3 gene, both at RNA and protein level in DM1, has been previously described (28, 36). This finding is confirmed by the present qRT-PCR experiments on muscle biopsies from DM1 patients. also Despite up-regulation upon denervation and hyperexcitability, the absence of SK3 protein in a myotonic mouse (ADR) suggests that its over-expression in DM1 might be related to a differentiation defect (36). SK3 might, therefore, play a key role in DM1 pathogenesis, more than being a mere downstream target of disordered myocytes. Among other functions, SK channels have been found to play a prominent role in cardiac myocytes (37). In the mouse heart, SK3 showed homogeneous levels of expression both in the atria and ventricules and an intermediate sensitivity to apamin (37).