TLX1 and acute lymphoblastic leukemia: Additionally, the doxycyline repressible tet-TLX1 transgenic mice subsequently acquire activating NOTCH1 mutations, consistent with reports that more than 50% of T-ALL patients carry NOTCH1 activating mutations [13] and that NOTCH1 and TLX1 can coregulate transcription in T-ALL cells [14].