INS and obesity due to melanocortin 4 receptor deficiency: There is suggestive evidence that this variant contributes to the obesity of the NZO strain, since the Lepr locus appeared to enhance the effect of the QTL Nob1 (later identified as Tbc1d1) on body weight and serum insulin in female (SJLxNZO)NZO backcross mice (Kluge et al. 2000).