JAK2 and myeloproliferative neoplasm: The GCC genotype is strongly associated with JAK2 V617F-positive MPNs (OR: 3.07; 95% CI: 1.73-5.46) and modestly associated with JAK2 V617F-negative MPN (OR: 2.26, 95% CI: 1.01-4.7) compared to normal controls (Table 3).