Wertheimer E, Litvin Y, Ebstein R P, Bennet E R, Barbetti F, Accili D, Taylor S I
Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland 20892.
J Clin Endocrinol Metab. 1994 May;78(5):1153-8. doi: 10.1210/jcem.78.5.8175972.
Molecular scanning techniques, such as denaturing gradient gel electrophoresis (DGGE), greatly facilitate screening candidate genes for mutations. We have used DGGE to screen for mutations in the insulin receptor gene in a family in which four of five daughters were affected by type A insulin resistance in association with acanthosis nigricans and hyperandrogenism. DGGE did not detect mutations in any of the 22 exons of the insulin receptor gene. Nevertheless, Southern blot analysis suggested that there was a deletion of exon 3 in the other paternal allele of the insulin receptor gene. Analysis of the father's cDNA confirmed that exon 3 was deleted from mRNA molecules derived from one of his two alleles of the insulin receptor gene. Furthermore, the father was found to be hemizygous for a polymorphic sequence (GACAsp at codon 234) in exon 3 that was not inherited by any of the five daughters. Instead, all five daughters inherited the paternal allele with the deletion mutation. We did not detect mutations in the mother's insulin receptor gene. Furthermore, the clinical syndrome did not segregate with either of the mother's two alleles of the insulin receptor gene. Although the youngest daughter inherited the mutant allele from her father, she was not clinically affected. The explanation for the incomplete penetrance is not known. These results emphasize the importance of specifically searching for deletion mutations when screening candidate genes for mutations. Furthermore, the existence of apparently asymptomatic carriers of mutations in the insulin receptor gene, such as the father in the present study, suggests that the prevalence of mutations in the insulin receptor gene may be higher than would be predicted on the basis of the observed prevalence of patients with extreme insulin resistance.
分子扫描技术，如变性梯度凝胶电泳（DGGE），极大地促进了对候选基因突变的筛选。我们利用DGGE在一个家庭中筛选胰岛素受体基因的突变，该家庭的五个女儿中有四个患有A型胰岛素抵抗，并伴有黑棘皮病和高雄激素血症。DGGE未在胰岛素受体基因的22个外显子中检测到任何突变。然而，Southern印迹分析表明，胰岛素受体基因的另一个父本等位基因中存在外显子3的缺失。对父亲cDNA的分析证实，外显子3从其胰岛素受体基因两个等位基因之一衍生的mRNA分子中缺失。此外，发现父亲在外显子3中一个多态性序列（密码子234处为GACAsp）上是半合子，五个女儿均未遗传该序列。相反，所有五个女儿都遗传了带有缺失突变的父本等位基因。我们未在母亲的胰岛素受体基因中检测到突变。此外，临床综合征与母亲胰岛素受体基因的两个等位基因均不连锁。尽管最小的女儿从父亲那里遗传了突变等位基因，但她并未出现临床症状。不完全外显的原因尚不清楚。这些结果强调了在筛选候选基因突变时专门寻找缺失突变的重要性。此外，胰岛素受体基因中存在明显无症状的突变携带者，如本研究中的父亲，这表明胰岛素受体基因突变的患病率可能高于基于观察到的极端胰岛素抵抗患者患病率所预测的水平。
