Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant disease caused by abnormal CAG repeat expansion in the ataxin 1 gene (ATXN1). The presence of CAT interruption(s) is important for diagnosing SCA1 in patients with 39-44 repeat alleles, as only uninterrupted alleles are considered abnormal. Determining the CAT interruption status might also be important for patients with >44 repeats, as the length of the longest uninterrupted CAG repeat stretch has been correlated with age at SCA1 onset. We detected CAT interruption(s) in the archived samples of Korean SCA1 patients using a traditional restriction enzyme method and validated the usefulness of a fluorescence-based tethering PCR procedure. Among the 2,312 alleles analyzed from 1,156 patients, we found 17 expanded alleles with ≥39 repeats, 71% of which harbored 39-44 repeats. Restriction enzyme method of six samples (four with 39-44 repeats and two with >44 repeats) revealed that none of the expanded alleles had CAT interruption(s). Tethering PCR showed the characteristic electropherogram pattern expected without CAT interruption(s). Along with the enzyme restriction method, tethering PCR can be applied to determine the number of allele repeats and provide information on CAT interruption(s) in clinical laboratories.

中文翻译：

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韩国脊髓小脑性共济失调 1 型患者 ATXN1 CAT 中断的检测方法和现状。

脊髓小脑性共济失调 1 型 (SCA1) 是一种常染色体显性遗传病，由 ataxin 1 基因 ( ATXN1 ) 异常 CAG 重复扩增引起。）。CAT 中断的存在对于诊断具有 39-44 个重复等位基因的患者的 SCA1 很重要，因为只有不间断的等位基因被认为是异常的。确定 CAT 中断状态对于重复次数 > 44 的患者也可能很重要，因为最长的不间断 CAG 重复拉伸的长度与 SCA1 发病时的年龄相关。我们使用传统的限制性内切酶方法在韩国 SCA1 患者的存档样本中检测到 CAT 中断，并验证了基于荧光的束缚 PCR 程序的有用性。在从 1,156 名患者分析的 2,312 个等位基因中，我们发现 17 个扩展的等位基因具有≥39 个重复，其中 71% 具有 39-44 个重复。六个样品的限制性内切酶法（四个具有 39-44 重复，两个具有 > 44 次重复）表明没有一个扩展的等位基因有 CAT 中断。Tethering PCR 显示了预期的特征电泳图谱，没有 CAT 中断。除了酶切限制方法外，tethering PCR 还可用于确定等位基因重复的数量并提供临床实验室中 CAT 中断的信息。