CRYL1 and obesity due to melanocortin 4 receptor deficiency: In this context, large-scale genomic studies identified obesity-related SNPs for genes of Melanocortin-4 Receptor (MC4R), Cryptochrome (CRY), and caveolin (CAV) [23–25]. The identification of obesity-related SNPs led to the creation of the "gene-environment interaction" hypothesis [26].