SNPs located in intron1 of FTO have also been shown to affect the expression of neighboring genes such as Iroquois homeobox 3 (IRX3), Iroquois homeobox 5 (IRX5), and RPGR-Interacting Protein 1-Like (RPGRIP1L); another possible role of FTO in obesity is the regulation of macronutrient intake, as the FTO gene is expressed in the hypothalamus during starvation. Here, IRX5 is linked to obesity due to melanocortin 4 receptor deficiency.