IntroductionThe genetic basis for human obesity is largely unknown. Recently mutations in the gene encoding the melanocortin 4 receptor (MC4R) are reported to be associated with the most common monogenic form of obesity in both humans and rodents. The MC4R belongs to the large superfamily of G protein-coupled receptors (GPCRs). It is found that 2-6% of severely obese individuals are heterozygous for functionally relevant non-synonymous, frameshift and nonsense MC4R mutations. Up to now most screening for MC...