Nucleofection of NmeCas9 ribonucleoprotein (RNP) (loaded with an in vitro-transcribed sgRNA) led to indel formation at three sites in K562 chronic myelogenous leukemia cells and in hTERT-immortalized human foreskin fibroblasts (gift from Dr. Job Dekker) (Fig. 1f). Here, RNPC3 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.