Generation of an HLA class I–negative iPSC founder line. (A) Schematic illustration of the B2M locus, showing the location of the gRNA binding site (orange bar) and the protospacer adjacent motifs sequence (magenta) necessary to guide Cas9 to its cleavage site (red arrow head). ATG start codon for β₂M translation is highlighted in red. Green arrow indicates an insertion or deletion (indel) is expected to be introduced into the genome through non-homologous end joining DNA repair pathway to cause a frameshift mutation in the B2M gene. (B) Flow cytometry analysis demonstrating the loss of surface expression of both β₂M and HLA in B2M knockout (KO) cells. APC, allophycocyanin; FITC, fluorescein isothiocyanate; WT, wild-type.