C9orf72 and frontotemporal dementia: Eventually, DeJesus-Hernandez and colleagues observed the non-Mendelian inheritance of a GGGGCC hexanucleotide repeat, located in a non-coding region of the C9orf72 gene, in the large VSM-20 family (Vancouver, San Francisco and Mayo family 20) affected by FTD-ALS, with the intuition that the repeat expansion, which was identified in the parents but not in the affected children by using fluorescent PCR, was too large to be amplified by the PCR method and could only be identified by repeated-primed PCR assay and Southern blot analysis (DeJesus-Hernandez et al., 2011).