Though increased MTNR1B transcript levels and reduced MTNR1B function could both be implicated in T2D susceptibility if reduced MTNR1B function was accompanied by changes in MTNR1B subcellular localization or a secondary increase of protein levels, the data by Bonnefond and colleagues [65] is not consistent with this explanation. The gene discussed is MTNR1B; the disease is type 2 diabetes mellitus.