Department of Molecular Biology, Massachusetts General Hospital and Department of Genetics, Harvard Medical School, Boston, MA 02114, United States of America; Department of Biological Sciences, Wellesley College, 106 Central St., Wellesley, MA, 02481, United States of America.
Molecular Genetics Core Facility, Children's Hospital Boston, Boston, MA 02115, United States of America.
PLoS One. 2015 Apr 7;10(4):e0121489. doi: 10.1371/journal.pone.0121489. eCollection 2015.
Omenn syndrome is a primary immunodeficiency disorder, featuring susceptibility to infections and autoreactive T cells and resulting from defective genomic rearrangement of genes for the T cell and B cell receptors. The most frequent etiologies are hypomorphic mutations in "non-core" regions of the Rag1 or Rag2 genes, the protein products of which are critical members of the cellular apparatus for V(D)J recombination. In this report, we describe an infant with Omenn syndrome with a previously unreported termination mutation (p.R142*) in Rag1 on one allele and a partially characterized substitution mutation (p.V779M) in a "core" region of the other Rag1 allele. Using a cellular recombination assay, we found that while the p.R142* mutation completely abolished V(D)J recombination activity, the p.V779M mutation conferred a severe, but not total, loss of V(D)J recombination activity. The recombination defect of the V779 mutant was not due to overall misfolding of Rag1, however, as this mutant supported wild-type levels of V(D)J cleavage. These findings provide insight into the role of this poorly understood region of Rag1 and support the role of Rag1 in a post-cleavage stage of recombination.
欧门综合征是一种原发性免疫缺陷病，其特征为易感染和自身反应性 T 细胞，这是由于 T 细胞和 B 细胞受体的基因基因组重排缺陷所致。最常见的病因是 Rag1 或 Rag2 基因“非核心”区域的功能减弱突变，其蛋白产物是 V(D)J 重组细胞装置的关键成员。在本报告中，我们描述了一例欧门综合征婴儿，其 Rag1 基因的一个等位基因上存在一个以前未报道的终止突变（p.R142*），另一个等位基因上存在一个部分特征的取代突变（p.V779M）。使用细胞重组测定，我们发现虽然 p.R142*突变完全消除了 V(D)J 重组活性，但 p.V779M 突变导致 V(D)J 重组活性严重丧失，但不是完全丧失。V779 突变体的重组缺陷不是由于 Rag1 的整体错误折叠所致，因为该突变体支持 Rag1 的野生型 V(D)J 切割水平。这些发现提供了对 Rag1 这一理解甚少区域的作用的深入了解，并支持 Rag1 在重组的切割后阶段的作用。
