A two-base deletion -439delGC in the melanocortin-4 receptor promoter associated with early-onset obesity.
OBJECTIVE
Mutations in melanocortin-4 receptor (MC4R) are the most common genetic cause of human obesity. Mutations in MC4R promoter could also underlie obesity, but have so far not been reported. Transcription factor nescient helix-loop-helix 2 (Nhlh2) is a novel obesity candidate gene. We searched for mutations in MC4R promoter and Nhlh2 gene in 152 children with severe early-onset obesity. Lean subjects (n = 447) served as controls.


METHODS
MC4R promoter and Nhlh2 gene were investigated by sequencing. Gel shifts and reporter gene assays were used to investigate a deletion in MC4R promoter. Mutation carriers were carefully characterised. Weight charts from index patients and relatives were analysed.


RESULTS
We identified a deletion, -439delGC, in MC4R promoter in 2 severely obese, unrelated children and their family members, but not in controls. Index patients and mutation-carrying relatives were affected by early-onset obesity, while non-carriers had normal childhood weight development. The deletion is located at a potential Nhlh2-binding site and gel shift assays showed that Nhlh2 binds to this site. No significant differences in mutant compared to wild-type MC4R promoter activities were detected. No mutations were identified in Nhlh2 gene.


CONCLUSIONS
We report an MC4R promoter mutation, -439delGC, associated with early-onset obesity and show that transcription factor Nhlh2 recognises this site in vitro. Nhlh2 mutations unlikely underlie severe human obesity.
Valli-Jaakola
Kaisa
K
Department of Medicine and Research Program in Molecular Medicine, University of Helsinki, Helsinki, Finland.
Palvimo
Jorma J
JJ
Lipsanen-Nyman
Marita
M
Salomaa
Veikko
V
Peltonen
Leena
L
Kontula
Kimmo
K
Schalin-Jäntti
Camilla
C
D000293:Adolescent; D017668:Age of Onset; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D002648:Child; D020090:Chromosome Segregation; D015331:Cohort Studies; D005260:Female; D017353:Gene Deletion; D017930:Genes, Reporter; D005820:Genetic Testing; D006579:Heterozygote; D006801:Humans; D008297:Male; D009765:Obesity / Q000209:etiology* / Q000235:genetics*; D011401:Promoter Regions, Genetic; D044105:Receptor, Melanocortin, Type 4 / Q000235:genetics*
D051792:Basic Helix-Loop-Helix Proteins; D044105:Receptor, Melanocortin, Type 4; C470072:MC4R protein, human; C076747:NHLH2 protein, human