CD34 and mucopolysaccharidosis: Under our experimental conditions, we found that untreated MPS IVA fibroblasts exhibited a significant pro-apoptotic profile, which can be reverted upon co-culture with CRISPR/nCas9-edited CD34+ cells (Figure 4d); this further supports the determination that supplying the GALNS enzyme through ex vivo CRISPR/Cas9-based GT could be a promising approach for preserving cell survival.