Fig 1.
Representative autoradiographs of SP-PCR for progenitor allele estimation (ePAL) in four DM1 patients using two different DNA sources (left blood and right saliva).
The lower boundary of the allele distribution in each tissue was used to estimate the PAL. The bottom arrowhead indicates the PAL estimated in blood. In patients with blood ePAL < 150 CTG repeats (CR317 and CR145), the estimation of PAL using saliva was about the same, but in patients with an ePAL > 150 CTG repeats (CR333 and CR183) the ePAL measured in saliva was larger than in blood. The top arrowhead indicates the modal allele length for each tissue. For each sample, we indicate the ePAL measured in blood (ePAL), the age at sampling (Ages) and the age of onset (Ageo). The molecular weight marker sizes are shown converted to CTG repeat numbers.
Fig 2.
Comparison of the modal allele size, progenitor allele length (ePAL), and degree of somatic instability (SI) from two different DNA tissue sources of the same DM1 patient.
Panel A shows the comparison of the modal allele length in the two tissues analysed. The dashed line corresponds to the line of best for the correlation. Points above the solid line indicate larger modal allele length in saliva than in blood. Panel B shows the comparison of the ePAL in the two tissues analysed. The dashed line corresponds to the line of best fit for the correlation. Points above the solid line indicate larger ePALs in saliva than in blood. Panel C shows the comparison of the degree of SI in the two tissues analysed. The dashed line corresponds to the line of best fit for the correlation. Points below the solid line indicate a lower degree of SI in saliva than in blood. Panels in D show a diagrammatic comparison of the somatic instability degree (SI) and the estimated progenitor allele length (ePAL) from two different DNA sources of the 38 DM1 patients analysed in this project. The whiskers represent the SI range for each tissue of each patient, whereas the diamonds and triangles indicate the modal allele in saliva and blood respectively. For better comparison, samples were split over three graphs according to the ePAL measured in blood.
Table 1.
Regression models of the relationship between age at onset (Ageo) and the progenitor allele length (ePAL) estimated from two different DNA tissue sources of the same DM1 patient.
Fig 3.
Representative histograms showing the allele distributions in two tissue sources of six DM1 patients.
The header indicates the progenitor allele length estimated in blood (ePAL) for each patient and the probability value (p) of equal distributions in both sample sources, calculated using the t-statistic of Anderson-Darling (AD). Patients with blood ePAL < 150 CTG repeats show similar allele distributions, while non-congenital DM1 patients with an ePAL > 150 CTG repeats showed a higher degree of instability in blood. Congenital cases showed higher levels of instability in saliva than in blood (bottom right).
Table 2.
Regression models of the relationship between somatic instability (SI) in DNA observed in blood and saliva and the estimated progenitor allele length in blood (ePAL) and the age at sampling (Ages).
Table 3.
Mean methylation percentage in blood and saliva of congenital cases within two CTCF binding sites.
Fig 4.
Expansion models of the CTG repeat expansion in blood and saliva.
The top model was proposed previously for the mutational dynamics of the CTG repeat expansion in blood DNA (modified from [15]). Data from this study suggests that in saliva (lower model), the rate of expansion/contractions is different than in blood, triggering a faster movement of the lower boundary, a more compact allele distribution and faster progression to a normal distribution than in blood and with larger modal allele length in saliva with time. In both models, as the number of CTGs increases, the mean and modal alleles increase and their frequency decreases with time.