Igarashi Kento, Kobayashi Junya, Katsumura Takafumi, Urushihara Yusuke, Hida Kyohei, Watanabe-Asaka Tomomi, Oota Hiroki, Oda Shoji, Mitani Hiroshi
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan.
Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Kyoto, Japan.
PLoS One. 2017 Jan 20;12(1):e0170006. doi: 10.1371/journal.pone.0170006. eCollection 2017.
Nbs1 is one of the genes responsible for Nijmegen breakage syndrome, which is marked with high radiosensitivity. In human NBS1 (hNBS1), Q185E polymorphism is known as the factor to cancer risks, although its DSB repair defect has not been addressed. Here we investigated the genetic variations in medaka (Oryzias latipes) wild populations, and found 40 nonsynonymous single nucleotide polymorphisms (SNPs) in medaka nbs1 (olnbs1) gene within 5 inbred strains. A mutation to histidine in Q170 residue in olNbs1, which corresponds to Q185 residue of hNBS1, was widely distributed in the closed colonies derived from the eastern Korean population of medaka. Overexpression of H170 type olNbs1 in medaka cultured cell lines resulted in the increased accumulation of olNbs1 at laser-induced DSB sites. Autophosphorylation of DNA-dependent protein kinase at T2609 was suppressed after the γ-ray irradiation, which was followed by prolonged formation of γ-H2AX foci and delayed DSB repair. These findings suggested that the nonsynonymous SNP (Q170H) in olnbs1, which induced DSB repair defects, is specifically distributed in the eastern Korean population of medaka. Furthermore, examination using the variation within wild populations might provide a novel method to characterize a driving force to spread the disease risk alleles.
Nbs1是导致尼曼-匹克氏断裂综合征的基因之一，该综合征的特点是具有高放射敏感性。在人类NBS1（hNBS1）中，Q185E多态性被认为是癌症风险因素，尽管其双链断裂修复缺陷尚未得到研究。在此，我们研究了青鳉（Oryzias latipes）野生种群中的基因变异，在5个近交系的青鳉nbs1（olnbs1）基因中发现了40个非同义单核苷酸多态性（SNP）。olNbs1中与hNBS1的Q185残基相对应的Q170残基突变为组氨酸，在源自韩国东部青鳉种群的封闭群体中广泛分布。在青鳉培养细胞系中过表达H170型olNbs1导致olNbs1在激光诱导的双链断裂位点处的积累增加。γ射线照射后，DNA依赖性蛋白激酶在T2609处的自磷酸化受到抑制，随后γ-H2AX焦点形成延长，双链断裂修复延迟。这些发现表明，olnbs1中的非同义SNP（Q170H）诱导双链断裂修复缺陷，且在韩国东部青鳉种群中特异性分布。此外，利用野生种群中的变异进行检测可能提供一种新方法来表征疾病风险等位基因传播的驱动力。
