Intermediate-length CAG repeats in ATXN2 have been widely shown to be a risk factor for sporadic amyotrophic lateral sclerosis (SALS). To evaluate the association of ATXN2 intermediate-length CAG repeat alleles with an increased risk of SALS, we investigated distributions of CAG repeat alleles in 394 patients with SALS and 490 control individuals in the Japanese population. In the intermediate-length repeat units of 29 or more, we identified one SALS patient with 31 repeat units and two control individuals with 30 repeat units. Thus, no significant differences in the carrier frequency of intermediate-length CAG repeat alleles were detected between patients with SALS and control individuals. When we investigated the distribution of “large normal alleles” defined as ATXN2 CAG repeats ranging from 24 up to 33 in the Japanese population compared with those in other populations in previous studies, the frequency of large normal alleles was significantly higher in the European and North American series than in the Japanese series. Moreover, these frequencies in the Turkish, Chinese, Korean, and Brazilian (Latin American) series were also higher than that in the Japanese series. These results raise the possibility that the frequencies of large normal alleles in individual populations underlie the frequencies of ALS risk alleles in the corresponding populations.

中文翻译：

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ATXN2中等长度CAG重复与肌萎缩性侧索硬化症的关联与正常CAG重复等位基因在各个族裔人群中的分布相关。

ATXN2中的中等长度CAG重复已被广泛证明是散发性肌萎缩性侧索硬化症（SALS）的危险因素。为了评估ATXN2中度CAG重复等位基因与SALS风险增加的关联，我们调查了394例SALS患者和490例日本人群中CAG重复等位基因的分布。在29个或更多的中等长度重复单元中，我们鉴定出1个具有31个重复单元的SALS患者和2个具有30个重复单元的对照个体。因此，在患有SALS的患者和对照个体之间，未检测到中等长度CAG重复等位基因的载波频率的显着差异。当我们调查定义为ATXN2的“大正常等位基因”的分布时与先前研究中的其他人群相比，日本人群中的CAG重复序列范围从24到33，在欧洲和北美系列中，大型正常等位基因的频率明显高于日本系列。此外，土耳其语，中文，韩语和巴西（拉丁美洲）系列中的这些频率也高于日本系列中的频率。这些结果增加了个别人群中大的正常等位基因频率在相应人群中ALS风险等位基因频率之下的可能性。