Marcelli M, Tilley W D, Wilson C M, Wilson J D, Griffin J E, McPhaul M J
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-8857.
J Clin Invest. 1990 May;85(5):1522-8. doi: 10.1172/JCI114599.
Mutations of the androgen receptor that impair the action of 5 alpha-dihydrotestosterone and testosterone result in abnormal male sexual development. The definition of the organization of the androgen receptor gene has permitted us to examine its structure in nine patients with androgen resistance that exhibit absent 5 alpha-dihydrotestosterone binding in cultured fibroblasts (receptor-negative androgen resistance). Using labeled probes specific for each individual coding exon, we find no gross rearrangements, insertions, or deletions of the androgen receptor gene in these patients. To analyze the genetic defect in these receptor-negative patients, we used the polymerase chain reaction to amplify each individual exon of the androgen receptor gene in nine affected patients. In all patients, the size of each amplified exon segment was identical to that in normal individuals. The nucleotide sequence of the entire coding region of the androgen receptor was determined in one of these patients. A single nucleotide substitution was identified that results in a premature termination codon in exon 6 at amino acid 794. S1 nuclease protection assays demonstrated that normal levels of androgen receptor mRNA are present in skin fibroblasts of this patient. Transfection of a mutated androgen receptor cDNA containing a termination codon at position 794 into eukaryotic cells resulted in formation of a normal amount of receptor protein, as indicated by immunoblotting, but the expressed protein does not bind 5 alpha-dihydrotestosterone. These findings suggest that the presence of a premature termination codon at amino acid 794 of the androgen receptor is the cause of androgen resistance in this patient.
雄激素受体的突变会损害5α-二氢睾酮和睾酮的作用，导致男性性发育异常。雄激素受体基因结构的明确使我们能够对9例雄激素抵抗患者的基因结构进行研究，这些患者在培养的成纤维细胞中表现出5α-二氢睾酮结合缺失（受体阴性雄激素抵抗）。使用针对每个编码外显子的特异性标记探针，我们发现这些患者的雄激素受体基因没有明显的重排、插入或缺失。为了分析这些受体阴性患者的基因缺陷，我们使用聚合酶链反应扩增了9例受影响患者雄激素受体基因的每个外显子。在所有患者中，每个扩增的外显子片段大小与正常个体相同。我们测定了其中1例患者雄激素受体整个编码区的核苷酸序列。发现了一个单核苷酸替换，该替换导致外显子6中第794位氨基酸处出现提前终止密码子。S1核酸酶保护试验表明，该患者皮肤成纤维细胞中存在正常水平的雄激素受体mRNA。将在第794位含有终止密码子的突变雄激素受体cDNA转染到真核细胞中，免疫印迹显示形成了正常量的受体蛋白，但表达的蛋白不结合5α-二氢睾酮。这些发现表明，雄激素受体第794位氨基酸处存在提前终止密码子是该患者雄激素抵抗的原因。
