C9orf72 HRE reactions

C9orf72 HRE genotyping⁸ was performed on blood DNA samples (or sampling of the cervical area of the cerebellum if blood was not available) to accurately size germline hexanucleotide repeat alleles. Repeat-primed PCR (RPPCR)⁹ was performed on all sampled sections of each patient to assess for the C9orf72 HRE and to estimate the lengths of C9orf72 alleles in each section. GeneMapper v4.0 (Applied Biosystems) was used to visualize and estimate reaction fragment sizes. Lengths of C9orf72 hexanucleotide repeat amplicons were measured using GeneMapper compared to the GeneScan-500 LIZ Size Standard (Applied Biosystems). Peaks from the RPPCR profiles were chosen based on the genotyping method results to represent C9orf72 alleles, which were plotted to assess variation within normal-length C9orf72 hexanucleotide repeat lengths.