Matthews P M, Brown R M, Otero L, Marchington D, Leonard J V, Brown G K
Department of Biochemistry, University of Oxford, UK.
Neurology. 1993 Oct;43(10):2025-30. doi: 10.1212/wnl.43.10.2025.
We describe a girl with developmental abnormalities of the CNS and a lactic acidosis whose cultured fibroblasts showed a profound deficiency of pyruvate dehydrogenase complex (PDHC) activity (patient = 0.14 nmol/mg protein per minute, controls = 0.7 to 1.1 nmol/mg protein per minute). Immunocytochemistry demonstrated the fibroblast culture to be mosaic, with 14% of cells expressing the PDHC E1 alpha subunit protein in normal amounts and the remaining 86% having no detectable immunoreactive activity. Direct sequencing of cDNA for the X-linked PDHC E1 alpha subunit established that the patient was heterozygous for a 20-bp deletion beginning in the codon for Ser300 of the derived amino acid sequence. The pattern of methylation at the DXS255 locus suggested predominant expression of the X chromosome carrying the mutant allele in the fibroblast culture. There was a good correlation between the residual PDHC activity, the proportion of cells with immunoreactive E1 alpha protein, and the X chromosome inactivation ratio, demonstrating the importance of X-inactivation for expression of this X-linked neurometabolic disease in females.
我们描述了一名患有中枢神经系统发育异常和乳酸性酸中毒的女孩，其培养的成纤维细胞显示丙酮酸脱氢酶复合体（PDHC）活性严重缺乏（患者 = 0.14 nmol/mg蛋白每分钟，对照组 = 0.7至1.1 nmol/mg蛋白每分钟）。免疫细胞化学显示成纤维细胞培养物呈镶嵌性，14%的细胞以正常量表达PDHC E1α亚基蛋白，其余86%未检测到免疫反应活性。对X连锁的PDHC E1α亚基的cDNA进行直接测序确定，患者在推导的氨基酸序列中Ser300密码子起始处有一个20 bp的缺失，为杂合子。DXS255位点的甲基化模式表明，在成纤维细胞培养物中携带突变等位基因的X染色体占主导表达。残余的PDHC活性、具有免疫反应性E1α蛋白的细胞比例和X染色体失活率之间存在良好的相关性，证明了X染色体失活对女性这种X连锁神经代谢疾病表达的重要性。
