To gain insights into the molecular link between TGDS deficiency and GAG synthesis, we inactivated TGDS using CRISPR–Cas9 in a range of cell lines: the colorectal carcinoma cell line HCT116, the osteosarcoma cell line U2OS, the chronic myeloid lymphoma cell line HAP1 and the human embryonic kidney cell line 293T (Extended Data Fig. 1a). Here, TGDS is linked to osteosarcoma.