Knockout of SNORD42A inhibits cell proliferation and colony-forming ability. (A) Three gRNAs were used for a single knockout of SNORD42A. Sanger sequencing confirmed genomic mutations for 2 out of the 3 gRNAs tested. (B) Relative expression of SNORD42A in Kasumi-1 cells. RT-PCR was performed with a mixed pool of cells with either CRISPR-Cas9 SNORD42A knockout or scrambled control. Data are shown as mean ± SD from 3 biological replicates. *P < .05, Student t test. (C) Proliferation assay from control and SNORD42A knockout cells in Kasumi-1 and MV4-11 cells. Data are shown as mean ± SD from 3 experiments. *P < .05, **P < .01, Student t test. dpi, days postinfection. (D) Colony-formation assay from control and SNORD42A knockout cells in Kasumi-1 and MV4-11 cells. 300 cells were seeded in methylcellulose. Only colonies with ≥50 cells were counted as colony (microscope: Zeiss AxioVert.A1, objective 2.5×; camera: Zeiss AxiocamMRm). Data are shown as mean ± SD from 3 biological replicates. *P < .05, **P < .01, Student t test.