Overview of repeats
Familial adult myoclonic epilepsy type 6 (FAME6) is was described by Ishiura and colleagues (2018), caused by insertions of expanded TTTCA repeats into the intron of the TNRC6A gene. They were able to find 5 affected individuals from one family who carried the mutation. The expanded allele size was determined to be around 5.6 kb longer than the normal one, corresponding to approximately 1100 pentanucleotide repeats. The configuration of the repeat was determined to be the following: (TTTTA)22(TTTCA)exp(TTTTA)exp. TTTCA expansions were not found in any of the 1000 control samples. The endogenous TTTTA repeat was expanded in nine healthy subjects, where in seven of them it was in the range of 40-120 repeats and in two individuals potentially even longer (Ishiura et al., 2018).