C9orf72 and frontotemporal dementia: Although there are other data analysis programs available for the analysis of triplet repeat expansions such as RepeatHMM [19] and Repeat Detector [20], we chose STRique [16] to measure the size of the CTG18.1 repeat sequences in TCF4. STRique had previously been used to study the hexanucleotide repeat expansion within C9ORF72, which causes frontotemporal dementia and amyotrophic lateral sclerosis (MIM #105550) [16].