Ku N O, Gish R, Wright T L, Omary M B
Gastroenterology Section, Palo Alto Veterans Affairs Medical Center and Stanford University School of Medicine, Calif 94304, USA.
N Engl J Med. 2001 May 24;344(21):1580-7. doi: 10.1056/NEJM200105243442103.
About 10 percent of patients who undergo liver transplantation have cryptogenic liver disease. In animal models, the absence of heteropolymeric keratins 8 and 18 or the presence of mutant keratins in hepatocytes causes or promotes liver disease. We have previously described a mutation in the keratin 18 gene in a patient with cryptogenic cirrhosis, but the importance of mutations in the keratin 8 and keratin 18 genes in such patients is unclear.
We tested for mutations in the keratin 8 and keratin 18 genes in purified genomic DNA isolated from 150 explanted livers and 89 peripheral-blood specimens from three groups of patients: 55 patients with cryptogenic liver disease; 98 patients with noncryptogenic liver disease, with causes that included alcohol use, autoimmunity, drug use, and viral infections; and 86 randomly selected inpatients and outpatients who provided blood to the hematology laboratory.
Of the 55 patients with cryptogenic liver disease, 3 had glycine-to-cysteine mutations at position 61 (a highly conserved glycine) of keratin 8, and 2 had tyrosine-to-histidine mutations at position 53 of keratin 8. These mutations were not detected in the patients with other liver diseases or in the randomly selected patients. We verified the presence of the mutations in specimens of explanted livers by protein analysis and by the detection of unique restriction-enzyme cleavage sites. In transfected cells, the glycine-to-cysteine mutation limited keratin-filament reorganization when the cells were exposed to oxidative stress. In contrast, the tyrosine-to-histidine mutation destabilized keratin filaments when transfected cells were exposed to heat or okadaic acid stress.
Mutations in the keratin 8 gene may predispose people to liver disease and may account for cryptogenic liver disease in some patients.
接受肝移植的患者中约10%患有隐源性肝病。在动物模型中,肝细胞中缺乏异源多聚角蛋白8和18或存在突变角蛋白会导致或促进肝病。我们之前曾描述过一名隐源性肝硬化患者的角蛋白18基因突变,但此类患者中角蛋白8和角蛋白18基因突变的重要性尚不清楚。
我们对从三组患者的150份肝移植切除肝脏标本和89份外周血标本中分离出的纯化基因组DNA进行角蛋白8和角蛋白18基因突变检测:55例隐源性肝病患者;98例非隐源性肝病患者,病因包括酒精使用、自身免疫、药物使用和病毒感染;以及86名随机选取的向血液学实验室献血的住院和门诊患者。
在55例隐源性肝病患者中,3例在角蛋白8的61位(一个高度保守的甘氨酸)发生了甘氨酸到半胱氨酸的突变,2例在角蛋白8的53位发生了酪氨酸到组氨酸的突变。在其他肝病患者或随机选取的患者中未检测到这些突变。我们通过蛋白质分析和检测独特的限制性酶切位点,在肝移植切除肝脏标本中证实了这些突变的存在。在转染细胞中,当细胞暴露于氧化应激时,甘氨酸到半胱氨酸的突变限制了角蛋白丝的重组。相反,当转染细胞暴露于热或冈田酸应激时,酪氨酸到组氨酸的突变使角蛋白丝不稳定。
角蛋白8基因突变可能使人们易患肝病,并可能是一些患者隐源性肝病的病因。