Recipients of Kat6a–/–Kat6b+/+ foetal liver cells reached the ethical endpoint within 21 days (p < 10–6; Fig. 3d), exhibiting anaemia (p = 10–6; Fig. 3e) and minimal contribution of the foetal liver donor cells to the recipient peripheral blood (Supplementary Fig. 5a). The gene discussed is KAT6B; the disease is anemia.