INS and diabetes mellitus: All the mice reliably develop insulitis between 3-4 weeks of age, all progress to severe insulitis by 6 weeks of age, followed by progressive and synchronous decrease of insulin mRNA in islets, leading to overt diabetes by 10-14 weeks of age in ~100% mice (67), regardless of colony locations (UChicago, UCSF, Stanford, Baylor, and Indiana Univ), sex, cage, bedding, water, diet, and enrichment.