Genetic screening for melanocortin-4 receptor mutations in a cohort of Italian obese patients: description and functional characterization of a novel mutation.
Mutations in the human melanocortin-4 receptor (MC4-R) gene may account for up to 5.8% of morbid nonsyndromic obesity. We have screened 120 unrelated obese patients for variants of the MC4-R gene. Four heterozygous missense variants were detected, including two polymorphisms (Val(103)Ile and Ile(251)Leu) previously described in the literature. A novel heterozygous mutation (Glu(308)Lys) was detected in a 36-yr-old female patient. Compared with the wild-type receptor, cells expressing the mutated receptor showed a reduced stimulation of cAMP production and a reduction of radioactive alpha MSH binding. No segregation of the mutation with the obese phenotype could be demonstrated. A second, potentially pathogenic mutation (Ser(30)Phe) was detected in a 31-yr-old female patient. Functional analysis of the mutated receptor showed no change in the affinity to the natural ligand alpha MSH nor limited ability to stimulate cAMP production. Sixty lean subjects were also screened, and no additional variants of the MC4-R gene were observed, except for two individuals with the Val(103)Ile polymorphism. In conclusion, we have screened a population of Italian obese subjects for MC4-R variants, demonstrating a 1.7% prevalence of potentially pathogenic mutations. A novel heterozygous missense mutation (Glu(308)Lys) that impairs MC4-R functional activity in vitro was characterized.
Santini
Ferruccio
F
Department of Endocrinology and Metabolism, University of Pisa, 56124 Pisa, Italy. fsantini@endoc.med.unipi.it
Maffei
Margherita
M
Ceccarini
Giovanni
G
Pelosini
Caterina
C
Scartabelli
Giovanna
G
Rosellini
Veronica
V
Chiellini
Chiara
C
Marsili
Alessandro
A
Lisi
Simonetta
S
Tonacchera
Massimo
M
Agretti
Patrizia
P
Chiovato
Luca
L
Mammoli
Claudia
C
Vitti
Paolo
P
Pinchera
Aldo
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D019556:COS Cells; D002648:Child; D002522:Chlorocebus aethiops; D015331:Cohort Studies; D005260:Female; D005820:Genetic Testing; D018698:Glutamic Acid / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D007558:Italy; D008239:Lysine / Q000235:genetics; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics / Q000502:physiology; D020125:Mutation, Missense; D009765:Obesity / Q000235:genetics*; D010375:Pedigree; D010649:Phenylalanine / Q000235:genetics; D044105:Receptor, Melanocortin, Type 4 / Q000235:genetics*; D012694:Serine / Q000235:genetics
D044105:Receptor, Melanocortin, Type 4; D018698:Glutamic Acid; D012694:Serine; D010649:Phenylalanine; D008239:Lysine