FIG. 2.

Quantitative identification of maternal and paternal 15q duplications. Arrow heads indicate relative signal intensity between the two melting curves. (a) Quantitative HRM determination of parental origin using normalized melt profiles. Bisulfite-treated DNA samples from 28 individuals with interstitial duplications of unknown origin were analyzed by quantitative HRM and compared to AS deletion (red) and PWS-UPD (dark green) controls. One nonduplicated control DNA sample is indicated in gray at ∼50% relative signal intensity. Normalized melting profiles revealed a clear grouping of 26 maternal duplication samples (blue) at an average relative signal intensity of ∼66% and a grouping of 2 paternal duplication samples (green) at a relative signal intensity of ∼40%. (b) Detection of parental origin in stable inherited interstitial 15q duplications. HRM normalization analysis in a family, where the child (blue = 66% relative signal intensity) has inherited a maternal duplication and his mother (green = 39% relative signal intensity) a duplication of paternal origin. As expected, the father, who does not have a chromosomal duplication, showed a relative signal intensity of 52%, within the 52%–60% range found in normal controls. (c) Quantitative HRM can determine both parental origin and distinguish between interstitial and isodicentric duplications on 15q. The colors indicate HRM analysis in AS deletion (red), PWS UPD (dark green), nonduplication control samples (gray), and maternal interstitial duplication (blue). The two known isodicentric duplication samples are indicated in pink. One sample had an HRM relative signal intensity of 73%, indicating a 2.7:1 ratio of maternal to paternal signal, while the other had a signal intensity of 87%, consistent with a 6.7:1 maternal-to-paternal ratio. Both isodicentric 15q duplication samples showed relative signal intensities >66%, the observed interstitial duplication relative signal intensity.