Skip to main content
. 2018 Nov;20(6):871–882. doi: 10.1016/j.jmoldx.2018.07.001

Figure 3.

Figure 3

Result comparisons for two discordant samples. A: The electropherograms are shown for two samples (ND001 and ND002), tested by the Penn-C9 repeat-primed PCR (RP-PCR) assays, reverse RP-PCR (RvRP-PCR), and AmplideX-C9, with the result interpretation for each reaction indicated to the right of each panel. An expansion is not detected for either sample using the Penn-C9 RP-PCR (false negative), whereas using the Penn-C9 RvRP-PCR assay with upstream instead of downstream primers, the characteristic saw-tooth pattern of a repeat expansion is seen for both samples. Using AmplideX-C9, the expansion in ND002 is not detected; however, a low-amplitude peak pattern is seen for ND001, which is interpreted as indeterminate for an expansion. The sequence variation responsible for the false-negative downstream PCR results has not yet been fully characterized. B: Southern blot hybridization with a repeat probe confirms the C9orf72 expansion in ND001 and ND002. Brackets indicate the size ranges of C9orf72 repeat expansion with somatic mosaicism. +Control, DNA from a C9orf72 expansion-positive control lymphoblast cell line; Marker, DIG molecular-weight marker.