Somatic mosaicism containing double mutations in PTCH1 revealed by generation of induced pluripotent stem cells from nevoid basal cell carcinoma syndrome

As next generation sequencers are widely used, somatic mosaicism is thought to be more common than previously expected. We report a mosaic patient with nevoid basal cell carcinoma syndrome, a genetic condition featured by minor anomalies and high prevalence of cancers such as basal cell carcinoma and medulloblastoma. The patient had a germline PTCH1 mutation, c.272delG, and a low prevalence somatic mutation, c.274delT. Since two mutations are located in close proximity, reversion error is likely to be involved in this event rather than a spontaneous mutation. This study is also unique in that mosaicism was initially identified by analysis of iPS cell clones derived from a single cell. (By Prof. Toshiyuki Miyashita, http://jmg.bmj.com/content/early/2017/03/31/jmedgenet-2016-104490 )