POT1 and B-cell chronic lymphocytic leukemia: By performing whole-exome sequencing of CLL families, loss-of-function mutations in Protection of Telomeres 1 (POT1) and other components of the shelterin complex have been demonstrated.8▪,9 As well as providing support for the role of rare variants these findings further highlight telomere dysregulation as a key process in CLL development.