CTCF and acute lymphoblastic leukemia: To determine the functional consequences of CTCF ZF mutations, we examined missense mutations that had been detected in acute lymphoblastic leukaemia (ALL) samples: L309P (T-ALL; Mullighan unpublished), R339Q [39], R377H [44] and G420D (diagnosis and relapsed hyperdiploid B-ALL; Mullighan unpublished) (Fig. 2A, Supplementary Table 1).