CD34 and thalassemia: According to our previous work, we investigated maximizing editing efficiency in HSCs [12], and designed seven β0 4142-targeting single guide RNAs (sgRNAs) co-delivered with the 3NLS Cas9 protein to CD34+ HSPCs of thalassemia patient Donor #1, who carried a homozygous mutation at the CD4142 site on the HBB gene (Fig. 1A and 1B; see details in Tables S1 and S2).