Activating JAK1 mutations and inactivation of PTPN2 occur together in T-ALL patients. (A) Quantitative PCR analysis confirmed an abnormal copy number of PTPN2 in 5 T-ALL cases. Patients 14, 17, and 18 displayed biallelic loss and patients 15 and 16 monoallelic loss of PTPN2. RNMT was used as control gene and values were normalized to a control individual (○). Patient 1 is shown as positive control and was described previously (red circles).15 *Analyzed diagnosis sample of patient 16 contained only 60% leukemic cells. (B) Sequence analysis of T-ALL patients with PTPN2 inactivation (n = 18) identified a heterozygous point mutation in the pseudokinase domain of JAK1 (exon 14) in patient 13. The c.1953T > C change results in the amino acid substitution p.Y652H. Patient 6 harbored a novel point mutation in one allele of JAK1 (c.1944A > C), which resulted in the exchange of amino acid p.K648N.
