A systematic analysis of recombination activity and genotype-phenotype correlation in human recombination-activating gene 1 deficiency.

[omenn syndrome]

The recombination-activating gene (RAG ) 1 /2 proteins play a critical role in the development of T and B cells by initiating the VDJ recombination process that leads to generation of a broad T -cell receptor (TCR ) and B-cell receptor repertoire . Pathogenic mutations in the RAG 1 /2 genes result in various forms of primary immunodeficiency , ranging from T (-)B (-) severe combined immune deficiency to delayed -onset disease with granuloma formation , autoimmunity , or both . It is not clear what contributes to such heterogeneity of phenotypes .We sought to investigate the molecular basis for phenotypic diversity presented in patients with various RAG 1 mutations .We have developed a flow cytometry-based assay that allows analysis of RAG recombination activity based on green fluorescent protein expression and have assessed the induction of the Ighc locus rearrangements in mouse Rag 1 (-/-) pro-B cells reconstituted with wild-type or mutant human RAG 1 (hRAG 1 ) using deep sequencing technology .Here we demonstrate correlation between defective recombination activity of hRAG 1 mutant proteins and severity of the clinical and immunologic phenotype and provide insights on the molecular mechanisms accounting for such phenotypic diversity .Using a sensitive assay to measure the RAG 1 activity level of 79 mutations in a physiologic setting , we demonstrate correlation between recombination activity of RAG 1 mutants and the severity of clinical presentation and show that RAG 1 mutants can induce specific abnormalities of the VDJ recombination process .