Rettenbacher E, Tarnow P, Brumm H, Prayer D, Wermter A-K, Hebebrand J, Biebermann H, Hinney A, Widhalm K
Department of Child and Adolescent Psychiatry, Rheinische Kliniken Essen, University of Duisburg-Essen, Germany.
Exp Clin Endocrinol Diabetes. 2007 Jan;115(1):7-12. doi: 10.1055/s-2007-949150.
Functionally relevant mutations in the melanocortin-4 receptor gene ( MC4R) currently display the most common major gene/allele effect on extreme obesity.
Mutation screen of the MC4R in consecutively ascertained Austrian children and adolescents with severe obesity, to analyse the phenotype of mutation carriers and to functionally characterise novel mutations.
102 unrelated extremely obese children and adolescents (mean BMI 33.5+/-7.1 kg/m(2), >97th centile; mean age 13.8+/-4.1 yr) and 109 parents (79 mothers/30 fathers) of 88 of these patients were studied. The MC4R coding region was screened using denaturing high-performance liquid chromatography (dHPLC); PCR products of aberrant dHPLC pattern were re-sequenced. Signal transduction properties of mutant MC4R was investigated by challenge with the highly potent agonist NDP-alpha-MSH. Cell surface expression was determined by ELISA. Magnetic resonance imaging (MRI) of the central nervous system (CNS) was applied to a 2.3 year old index patient. Body fat and bone mineral content were assessed in three of the five mutation carriers by dual energy x-ray absorptiometry (DEXA). Oral glucose tolerance test (OGTT) was applied to some mutation carriers.
Heterozygous carriers of two non-synonymous mutations, two polymorphisms and a silent variation were identified within the study group. (1) A novel MC4R non-synonymous mutation (S136F) was detected in a 2.3 year old girl with extreme obesity (BMI 33.2 kg/m(2), >99th centile); (2) a previously described non-synonymous mutation (V253I) was identified in an obese mother (BMI 28.1 kg/m(2)) who did not transmit this mutation to her extremely obese son; (3) two known polymorphisms (V103I and I251L) were also identified; and (4) one obese mother was carrier of a silent variation (c.594C>T; I198). Co-segregation of S136F with the obesity phenotype was shown for three generations. IN VITRO functional studies revealed a complete loss of signal transduction activity of the mutant receptor while cell surface expression was only slightly reduced compared to the wild-type receptor.
We detected a novel non-synonymous mutation (S136F) that leads to a complete loss of MC4R function IN VITRO.
黑皮质素-4受体基因（MC4R）中功能相关突变目前在极端肥胖方面表现出最常见的主要基因/等位基因效应。
对连续确诊的奥地利重度肥胖儿童和青少年进行MC4R突变筛查，分析突变携带者的表型并对新突变进行功能特性分析。
研究了102名无亲缘关系的极端肥胖儿童和青少年（平均BMI 33.5±7.1kg/m²，>第97百分位数；平均年龄13.8±4.1岁）以及其中88名患者的109名父母（79名母亲/30名父亲）。使用变性高效液相色谱法（dHPLC）筛查MC4R编码区；对dHPLC图谱异常的PCR产物进行重新测序。通过用高效激动剂NDP-α-MSH刺激来研究突变型MC4R的信号转导特性。通过酶联免疫吸附测定（ELISA）确定细胞表面表达。对一名2.3岁的索引患者进行中枢神经系统（CNS）的磁共振成像（MRI）检查。通过双能X线吸收法（DEXA）对5名突变携带者中的3名进行体脂和骨矿物质含量评估。对一些突变携带者进行口服葡萄糖耐量试验（OGTT）。
在研究组中鉴定出两个非同义突变、两个多态性和一个沉默变异的杂合携带者。（1）在一名2.3岁的极端肥胖女孩（BMI 33.2kg/m²，>第99百分位数）中检测到一个新的MC4R非同义突变（S136F）；（2）在一位肥胖母亲（BMI 28.1kg/m²）中鉴定出一个先前描述的非同义突变（V253I），她未将此突变传递给她极度肥胖的儿子；（3）还鉴定出两个已知的多态性（V103I和I251L）；（4）一位肥胖母亲是一个沉默变异（c.594C>T；I198）的携带者。S136F与肥胖表型在三代人中呈现共分离。体外功能研究显示突变受体的信号转导活性完全丧失，而与野生型受体相比细胞表面表达仅略有降低。
我们检测到一个新的非同义突变（S136F），该突变导致MC4R在体外功能完全丧失。
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