These “disallowed” (or “forbidden”) genes, of which 11 were common to the 2 studies above (5), include the lactate/pyruvate (monocarboxylate) transporter MCT-1, encoded by Slc16a1, as well as Ldha. Up-regulation of the human analog of the former is observed in cases of exercise-induced hyperinsulinism (10), in which activating mutations in the SLC16A1 promoter lead to the expression of MCT-1 in the β-cell plasma membrane. The gene discussed is SLC16A1; the disease is hyperinsulinism.