Rootwelt H, Berger R, Gray G, Kelly D A, Coşkun T, Kvittingen E A
Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Norway.
Am J Hum Genet. 1994 Oct;55(4):653-8.
In six unrelated patients with hereditary tyrosinemia type 1 (HT1), three different disease-causing mutations were found by DNA sequencing. Two Pakistani patients, with acute and intermediate forms of HT1, were homozygous for a G192-->T mutation in the last nucleotide of exon 2. This caused aberrant splicing with partial intron 2 retention and premature termination. Three Turkish patients with chronic and intermediate forms of HT1 were homozygous for an A698-->T mutation substituting aspartic acid 233 with valine. A Norwegian patient with an intermediate clinical phenotype was heterozygous for G786-->A, introducing a TGA stop codon for Trp262 (W262X). Site-directed mutagenesis and expression in a rabbit reticulocyte lysate system demonstrated that the nonsense and missense mutations abolished fumarylacetoacetase activity and gave reduced amounts of a truncated and a full-length protein, respectively. Simple tests were established to identify the three mutations by restriction digestion of PCR-amplified genomic DNA. Among 30 additional HT1 patients investigated, 2 were found to be homozygous and 1 heterozygous for G192-->T. Two other patients were homozygous and one was heterozygous for W262X.
在6名无关的1型遗传性酪氨酸血症（HT1）患者中，通过DNA测序发现了3种不同的致病突变。两名患有急性和中间型HT1的巴基斯坦患者，在外显子2最后一个核苷酸处发生G192→T突变，呈纯合状态。这导致异常剪接，部分保留了内含子2并提前终止。三名患有慢性和中间型HT1的土耳其患者，因A698→T突变呈纯合状态，该突变使天冬氨酸233被缬氨酸取代。一名具有中间临床表型的挪威患者为G786→A杂合子，引入了一个针对色氨酸262（W262X）的TGA终止密码子。定点诱变和在兔网织红细胞裂解物系统中的表达表明，无义突变和错义突变分别消除了富马酰乙酰乙酸酶活性，并使截短蛋白和全长蛋白的量减少。通过对PCR扩增的基因组DNA进行限制性消化，建立了简单的检测方法来鉴定这三种突变。在另外30名接受调查的HT1患者中，发现2名患者为G192→T纯合子，1名患者为杂合子。另外两名患者为W262X纯合子，一名患者为杂合子。
