Previously, in NOD/ShiLtJ mice that spontaneously developed type 1 diabetes, the possible involvement of decreased expression of LMP2/β1i, an immunoproteasome β subunit, and associated decreased expression of NF-κB1 (also known as p50) in the development of type 1 diabetes was investigated. The gene discussed is PSMB9; the disease is type 1 diabetes mellitus.