CTG expansion is enlarged from muscle to patient myoblast
To determine the degree of similarity in CTG expansion size between the isolated myoblasts and the muscle they originated from, a small pool PCR analysis was performed. We measured the progenitor allele in four of the five patients included in the study (Table 1). The myoblast pools were measured for the progenitor allele. In the case of P3 and P4, who showed clonal amplification of the expansion, only one CTG expanded band could be detected in the small pool PCR analysis. When comparing the size of the expanded allele in the myoblast pool and muscle from the same patient, no correlation was found. However, there were some myoblasts with expansion size very similar to the muscle tissue from which they derive. In all patients, myoblasts showed a tendency to have longer expanded alleles compared to the muscle tissue from which they were isolated. The CTG expansion size in muscle correlated with the age of symptom onset in the patients (p=0.05). No other correlation were found between CTG size and clinical or molecular data.