Identifying Novel DNA Damage Response Genes in Radiosensitive Individuals

Ionizing radiation is an effective therapeutic agent for cancer treatment as well as a potent carcinogen. Sensitivity to the cell-killing effects of radiation can vary across human population with a subset of individuals displaying extreme hypersensitivity. It is usually attributable to inherited defects in DNA damage response pathways. The present study was designed to elucidate the genetic basis of variation in hypersensitivity to radiation exposure through exome sequencing of radiosensitive individuals, with the ultimate goal of identifying genes with the most significant effects on cellular DNA damage responses. The study participants included subjects referred for clinical testing for Ataxia-telangiectasia (A-T), Nijmegen Breakage Syndrome (NBS) or Ligase IV Syndrome. These are rare, recessive genetic disorders and hypersensitivity to radiation exposure is a common phenotype among individuals affected by all the three disorders. The study participants exhibited phenotypic characteristics similar to individuals with A-T, NBS or Ligase IV Syndrome, but lacked the causative mutations in ATM (GeneID:472) or NBN (GeneID:4683) genes. For further validation of the radiation sensitivity phenotype among the enrolled subjects, B-lymphoblastoid cells lines were established for each subject from peripheral blood lymphocytes. Each cell line was evaluated for displaying impaired survival rates relative to normal controls after exposure to ionizing radiation. 53 subjects with validated phenotype were finally included in the study and DNA extracted from their B-lymphoblastoid cell lines was used for exome sequencing. This sequencing data for radiation sensitive subjects is being made available in the dbGaP. It is hoped that this resource will be beneficial for researchers who wish to further investigate components of human cellular DNA damage response pathways and/or genetic architecture underlying radiation hypersensitivity. This data may also aid in the rational design of new radiosensitizing or radioprotective agents. ]]>
Inclusion criteria: Subjects referred for clinical testing for Ataxia-telangiectasia, Nijmegen Breakage Syndrome or Ligase IV Syndrome were enrolled for the study. Of these, subjects whose B-lymphoblastoid cell lines displayed impaired survival relative to normal controls after exposure to ionizing radiation were included in the study. Exclusion criteria: Subjects with a previously detected recessive loss of function mutations in causative genes such ATM and NBN were excluded from the study. ]]>

电离辐射（Ionizing radiation）既是癌症治疗中的有效治疗手段，亦是一类强效的致癌物。人群对辐射杀伤细胞效应的敏感性存在显著个体差异，部分个体可表现出极端的辐射超敏反应。此类超敏反应通常源于DNA损伤应答通路的遗传性缺陷。本研究旨在通过对辐射敏感个体开展外显子组测序（exome sequencing），阐明辐射暴露超敏反应差异的遗传基础，最终目标是识别对细胞DNA损伤应答通路具有最显著调控效应的基因。

本研究的受试者均为接受共济失调毛细血管扩张症（Ataxia-telangiectasia, A-T）、尼杰梅根断裂综合征（Nijmegen Breakage Syndrome, NBS）或连接酶IV综合征（Ligase IV Syndrome）临床检测的个体。上述三类均为罕见的常染色体隐性遗传病，辐射暴露超敏是这三种疾病患者共有的典型表型。本研究纳入的受试者虽表现出与A-T、NBS或连接酶IV综合征患者相似的表型特征，但未携带ATM（GeneID:472）或NBN（GeneID:4683）基因的致病突变。

为进一步验证入组受试者的辐射敏感表型，研究人员从每位受试者的外周血淋巴细胞中建立了B淋巴母细胞系（B-lymphoblastoid cell lines）。针对每个细胞系，研究人员评估了其在电离辐射暴露后相较于正常对照的存活能力是否受损。最终共有53名表型验证合格的受试者纳入本研究，研究人员使用从其B淋巴母细胞系中提取的DNA完成了外显子组测序。

本研究产生的辐射敏感受试者测序数据已上传至dbGaP数据库。本数据集希望能够为致力于进一步解析人类细胞DNA损伤应答通路组分及辐射超敏相关遗传结构的研究人员提供助力。此外，该数据还有助于合理设计新型辐射增敏剂或辐射防护剂。

纳入标准：本研究纳入接受共济失调毛细血管扩张症、尼杰梅根断裂综合征或连接酶IV综合征临床检测的受试者。其中，B淋巴母细胞系在电离辐射暴露后相较于正常对照表现出存活能力受损的受试者，最终纳入本研究。

排除标准：既往已检出ATM、NBN等致病基因携带隐性功能丧失性突变的受试者，将其排除出本研究。