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.