Low frequency of melanocortin-4 receptor (MC4R) mutations in a Mediterranean population with early-onset obesity

BACKGROUND:Melanocortin-4 receptor (MC4R) mutations have been reported as the most common single genetic cause of obesity in some populations and it has been suggested that they may be responsible for more than 4% of early-onset obesity. OBJECTIVES:To verify the presence of mutations of the MC4R coding region in children from southern Italy with early-onset obesity. SUBJECTS AND METHODS:Two-hundred and eight unrelated obese children and adolescents were included in the study. The average age at obesity onset was 4.5+/-2.6 y. MC4R coding region was screened using both single-strand conformation polymorphism (SSCP) analysis and denaturing high-performance liquid chromatography (DHPLC). Automatic sequencing of PCR products of all individuals that showed an aberrant SSCP and/or DHPLC pattern was performed. RESULTS:One novel missense mutation and one previously described polymorphism (Vall03Ile) were identified. The missense mutation C142T, resulting in the substitution of proline with serine at codon 48, within the first MC4R transmembrane domain, was detected at the heterozygous state in a 15-y-old obese girl (body mass index (BMI)=35 kg/m(2)) who has been obese since she was 8 y old. The mutation co-segregated with the obesity phenotype for over three generations and was not found in the control population. CONCLUSIONS:Our data show MC4R obesity causing mutations in less than 0.5% of the patients (ie 1 out of 208 patients) and therefore indicate a low prevalence of MC4R variants in the obese population from southern Italy. The specific genetic background of the Mediterranean population could make it difficult for MC4R mutations to produce an essentially polygenic trait such as common obesity, at least during childhood.