NOTCH1 is mutated in a large fraction of RS cases and chemorefractory CLL. (a) Schematic diagram of the NOTCH1 gene (top) and protein (bottom), with its conserved functional domains (EGF-like repeats; LNR, LIN-12/NOTCH repeats; HD, heterodimerization; TM, transmembrane; Ank, Ankyrin repeats; TAD, transactivation; PEST). Color-coded shapes indicate the position of the mutations found in CLL at diagnosis, RS, and chemorefractory CLL. (b) Prevalence of NOTCH1 mutations in CLL at diagnosis, RS, chemorefractory CLL, and de novo DLBCL; numbers on top indicate the actual number of mutated samples over total analyzed. ***, P < 0.001; **, P < 0.05.