Zhang Ning, Sang Yi-Lin, Zhu Wu, Wang Yu-Rong, Yu Yan-Yan, Chen Ya-Hui, Du Juan, He Wen-Bin, Tan Yue-Qiu, Wang Fu-Yan
Department of Immunology, Xiangya School of Basic Medical Sciences, Central South University, Changsha, Hunan, 410013, People's Republic of China.
Institute of Reproductive and Stem Cell Engineering, Xiangya School of Basic Medical Sciences, Central South University, Changsha, Hunan, 410078, People's Republic of China.
Appl Clin Genet. 2025 Sep 6;18:175-187. doi: 10.2147/TACG.S525027. eCollection 2025.
X-linked severe combined immunodeficiency (X-SCID) is an inherited immune disorder caused by pathogenic variants in the gene, leading to recurrent infections. Identifying these variants and elucidating their pathogenic mechanisms are crucial for precise diagnosis and treatment, prenatal diagnosis, and preimplantation genetic testing (PGT). This study aimed to identify candidate variants in four families with suspected immunodeficiency, assess their pathogenicity, elucidate their pathogenic mechanisms, and provide a basis for precise treatment, prenatal diagnosis, and PGT.
Four families with suspected immunodeficiency were recruited from the Reproductive and Genetic Hospital of CITIC-Xiangya. Whole exome sequencing (WES) was used to identify the genetic etiology. Functional experiments were performed to assess the pathogenicity of the identified variants, and to elucidate their pathogenic mechanisms.
WES identified four variants: three hemizygous (c.569G>C:p.R190P, c.515T>C:p.L172P, c.217A>C:p.T73P) and one heterozygous (c.1091C>T:p.T364I) variants. Three of these variants were novel. Initially three variants (p.R190P, p.T73P, and p.T364I) were classified as variants of uncertain significance (VUS) and one (p.L172P) was likely pathogenic (LP) according to ACMG/AMP guidelines. Functional analyses revealed reduced STAT5 phosphorylation and transcriptional activity across all variants, supporting the reclassification of three variants (p.R190P, p.L172P, and p.T73P) as likely pathogenic (LP), and one variant (p.T364I) as VUS with a Bayesian score of 5. Furthermore, IP-MS analysis revealed that the mutant IL2RG resulted in reduced cell-surface expression and abnormal nuclear localization. Therefore, the identified variants impair IL-2-induced STAT5 phosphorylation and transcriptional activity to cause X-linked severe combined immunodeficiency in these families.
This study highlights the critical role of functional analysis in clarifying variant pathogenicity and provides a clear example of pathogenicity assessment for variants. Integrating genomic and functional data enhance diagnostic precision and informs precise treatment strategies, genetic counseling, prenatal diagnosis, and PGT for X-SCID.
X连锁重症联合免疫缺陷（X-SCID）是一种由该基因的致病变异引起的遗传性免疫疾病，可导致反复感染。识别这些变异并阐明其致病机制对于精确诊断和治疗、产前诊断以及植入前基因检测（PGT）至关重要。本研究旨在识别四个疑似免疫缺陷家庭中的候选变异，评估其致病性，阐明其致病机制，并为精确治疗、产前诊断和PGT提供依据。
从中信湘雅生殖与遗传医院招募了四个疑似免疫缺陷家庭。采用全外显子组测序（WES）来确定遗传病因。进行功能实验以评估所识别变异的致病性，并阐明其致病机制。
WES识别出四个IL2RG变异：三个半合子（c.569G>C:p.R190P、c.515T>C:p.L172P、c.217A>C:p.T73P）和一个杂合子（c.1091C>T:p.T364I）变异。其中三个变异是新发现的。根据美国医学遗传学与基因组学学会（ACMG）/美国分子病理学会（AMP）指南，最初三个变异（p.R190P、p.T73P和p.T364I）被分类为意义未明的变异（VUS），一个（p.L172P）可能致病（LP）。功能分析显示，所有变异均导致STAT5磷酸化和转录活性降低，支持将三个变异（p.R190P、p.L172P和p.T73P）重新分类为可能致病（LP），一个变异（p.T364I）为VUS，贝叶斯评分为5。此外，免疫沉淀-质谱（IP-MS）分析显示，突变的IL2RG导致细胞表面表达减少和核定位异常。因此，所识别的IL2RG变异损害了IL-2诱导的STAT5磷酸化和转录活性，从而在这些家庭中导致X连锁重症联合免疫缺陷。
本研究强调了功能分析在阐明变异致病性方面的关键作用，并为IL2RG变异的致病性评估提供了一个清晰的实例。整合基因组和功能数据可提高诊断准确性，并为X-SCID的精确治疗策略、遗传咨询、产前诊断和PGT提供信息。
