We provide evidence that Tcf19 expression is positively correlated with islet expansion in nondiabetic obesity (Fig. 2, A and B) and that Tcf19 expression increases in response to FoxM1 overexpression, a known driver of β-cell proliferation (Fig. 2, D and E). This evidence concerns the gene FOXM1 and obesity due to melanocortin 4 receptor deficiency.