Based upon a QTL analysis of modifiers of T2D in B6xDBA F2 Lepob/ob mice, we identified a novel gene, Lisch-like (Ll), whose apparent effect on β-cell development, and possibly other aspects of β-cell/islet biology, qualify it as a strong candidate mediator of susceptibility to T2D. This evidence concerns the gene ILDR2 and type 2 diabetes mellitus.