Myerowitz R
Laboratory of Biochemistry and Metabolism, National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1988 Jun;85(11):3955-9. doi: 10.1073/pnas.85.11.3955.
Tay-Sachs disease is an inherited disorder in which the alpha chain of the lysosomal enzyme beta-N-acetylhexosaminidase A bears the mutation. Ashkenazi Jews are found to be carriers for a severe type of Tay-Sachs disease, the classic form, 10 times more frequently than the general population. Ashkenazi Jewish patients with classic Tay-Sachs disease have appeared to be clinically and biochemically identical, and the usual assumption has been that they harbor the same alpha-chain mutation. In this study I have isolated the alpha-chain gene from an Ashkenazi Jewish patient, GM2968, with classic Tay-Sachs disease and compared its nucleotide sequences with that of the normal alpha-chain gene in the promoter region, exon and splice junction regions, and polyadenylylation signal area. Only one difference was observed between these sequences: at the 5' boundary of intron 12, a guanosine in the conserved splice junction dinucleotide sequence G-T had been altered to a cytidine. The alteration is presumed to be functionally significant and to result in aberrant mRNA splicing. Utilizing the polymerase chain reaction to amplify the region encompassing the mutation, I developed an assay to screen patients and heterozygote carriers for this mutation. Surprisingly, in each of two Ashkenazi patients, only one alpha-chain allele harbored the splice junction mutation. Only one parent of each of these patients was positive for the defect. Another Ashkenazi patient did not bear this mutation at all nor did either of the subject's parents. In addition, 30% of obligate heterozygotes tested carried the splice junction mutation, whereas 20 Ashkenazi Jews designated noncarriers by enzymatic assay were negative for this alteration. The data are consistent with the presence of more than one mutation underlying the classic form of Tay-Sachs disease in the Ashkenazi Jewish population.
泰-萨克斯病是一种遗传性疾病，其中溶酶体酶β-N-乙酰己糖胺酶A的α链发生了突变。发现阿什肯纳兹犹太人携带严重类型的泰-萨克斯病（经典型）的频率比普通人群高10倍。患有经典泰-萨克斯病的阿什肯纳兹犹太患者在临床和生化方面似乎是相同的，通常的假设是他们携带相同的α链突变。在本研究中，我从一名患有经典泰-萨克斯病的阿什肯纳兹犹太患者GM2968中分离出α链基因，并将其核苷酸序列与正常α链基因在启动子区域、外显子和剪接连接区域以及聚腺苷酸化信号区域的序列进行了比较。这些序列之间仅观察到一个差异：在内含子12的5'边界处，保守剪接连接二核苷酸序列G-T中的鸟苷被改变为胞苷。这种改变被认为在功能上具有重要意义，并导致异常的mRNA剪接。利用聚合酶链反应扩增包含该突变的区域，我开发了一种检测方法来筛查患者和杂合子携带者是否存在这种突变。令人惊讶的是，在两名阿什肯纳兹患者中，每个患者只有一个α链等位基因携带剪接连接突变。这些患者中只有一位父母的缺陷呈阳性。另一名阿什肯纳兹患者根本没有携带这种突变，其父母也没有。此外，30%接受检测的必然杂合子携带剪接连接突变，而通过酶学检测被指定为非携带者的20名阿什肯纳兹犹太人没有这种改变。这些数据与阿什肯纳兹犹太人群中经典型泰-萨克斯病存在不止一种突变的情况一致。
