Generation of CRISPR/Cas9 edited cell lines

Generation of CRISPR/Cas9 edited cell lines was carried out as described ⁵⁴ following standard protocols ⁵⁵ using the primers listed in Supplementary Table S7. Briefly, DNA repair templates were designed containing sequences homologous to the upstream and downstream regions of the targeting site separated by an insert containing stop codons in the three reading frames. The repair template and plasmids encoding the guide RNA (gRNA), Cas9 and a gene encoding puromycin resistance were transfected into HEK293T cells using lipofectamin 2000. The transfected cells were selected by puromycin treatment for 2 days and isolated clones were screened by PCR genotyping to identify cells with the inactivated gene of interest (Supplementary Figure S15) using the primers listed in Supplementary Table S7. In each case, several independently isolated clones were characterized for relevant phenotypes and found to have indistinguishable behavior.