Mutation screen and association studies in the diacylglycerol O-acyltransferase homolog 2 gene (DGAT2), a positional candidate gene for early onset obesity on chromosome 11q13

Background: DGAT2 is a promising candidate gene for obesity because of its function as a key enzyme in fat metabolism and because of its localization on chromosome 11q13, a linkage region for extreme early onset obesity detected in our sample. We performed a mutation screen in 93 extremely obese children and adolescents and 94 healthy underweight controls. Association studies were performed in samples of up to 361 extremely obese children and adolescents and 445 healthy underweight and normal weight controls. Additionally, we tested for linkage and performed family based association studies at four common variants in the 165 families of our initial genome scan. Results: The mutation screen revealed 15 DNA variants, four of which were coding non- synonymous exchanges: p. Val82Ala, p. Arg297Gln, p. Gly318Ser and p. Leu385Val. Ten variants were synonymous: c.- 9447A > G, c-584C > G, c-140C > T, c.- 30C > T, IVS2- 3C > G, c.812A > G, c.920T > C, IVS7+ 23C > T, IVS7+ 73C > T and * 22C > T. Additionally, the small biallelic trinucleotide repeat rs3841596 was identified. None of the case control and family based association studies showed an association of investigated variants or haplotypes in the genomic region of DGAT2. Conclusion: In conclusion, our results do not support the hypothesis of an important role of common genetic variation in DGAT2 for the development of obesity in our sample. Anyhow, if there is an influence of genetic variation in DGAT2 on body weight regulation, it might either be conferred by the less common variants (MAF < 0.1) or the detected, rare non-synonymous variants.