Splenic extramedullary hemopoiesis caused by a dysfunctional mutation in the NF-κB-inducing kinase gene

► We established a novel method for typing the aly mutation in the NIK gene. ► We established aly mutant mice on a BALB/cA background. ► The aly mutant mice exhibited splenomegaly and extramedullary hemopoiesis. ► NF-κB activation may be involved in suppressing extramedullary hemopoiesis.