Joanne Trinh and her group has identified a completely novel repeat interruption that exists in mosaic form within the expanded SINE-VNTR-Alu(AGAGGG)n repeat of TAF1. These repeat interruptions differ in repeat motif sequence and have been coined the new term mosaic Divergent Repeat Interruptions affecting both motif Length and Sequence (mDRILS)1. Their seminal work illustrates the importance of somatic mosaic genotypes, biological plausibility of multiple modifiers that can have additive effects on repeat instability, and that these variations may remain undetected without assessment of single molecules. The study has been published in Brain.