In agreement with the key role of MCPH1/BRIT1 in the regulation of cell cycle progression at the G2/M checkpoint, they found that chronic myeloid leukemia cells have a low level of MCPH1/BRIT1 and a defective G2/M arrest, confirming the genomic instability of these cells. The gene discussed is MCPH1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.