The association between the melatonergic system and T2D was further enhanced in a large-scale exon re-sequencing study of MTNR1B which revealed 40 non-synonymous variants of which the 36 very rare ones [minor allele frequency (MAF) < 0.1%] were significantly associated with T2D (Bonnefond et al., 2012). Here, MTNR1B is linked to type 2 diabetes mellitus.