Hypomorphic Rag1 mutations alter the pre-immune repertoire at early stages of lymphoid development

Lisa M. Ott de Bruin, Marita Bosticardo, Alessandro Barbieri, Sherry G. Lin, Jared H. Rowe, Pietro L. Poliani, Kimberly Ching, Daniel Eriksson, Nils Landegren, Olle Kämpe, John P. Manis and Luigi D. Notarangelo

Key points

  • Mice with hypomorphic mutations in the RAG1 C-terminal domain are a model of leaky combined immunodeficiency with autoantibodies

  • Hypomorphic C-terminal domain Rag1 mutations cause repertoire skewing at the earliest stages of B and T cell development.


Hypomorphic RAG1 mutations allowing residual T and B cell development have been found in patients presenting with delayed-onset combined immune deficiency with granulomas and/or autoimmunity (CID-G/AI) and abnormalities of the peripheral T and B cell repertoire. To examine how hypomorphic Rag1 mutations affect the earliest stages of lymphocyte development, we used CRISPR/Cas9 to generate mouse models with equivalent mutations found in patients with CID-G/AI. Immunological characterization showed partial development of T and B lymphocytes, with persistence of naïve cells, preserved serum immunoglobulin, but impaired antibody responses and presence of autoantibodies, thereby recapitulating the phenotype seen in patients with CID-G/AI. By using high throughput sequencing, we identified marked skewing of Igh V and Trb V gene usage in early progenitors, with a bias for productive Igh and Trb rearrangements after selection occurred and increased apoptosis of B cell progenitors. Rearrangement at the Igk locus was impaired, and polyreactive IgM antibodies were detected. This study provides novel insights in how hypomorphic Rag1 mutations alter the primary repertoire of T and B cells, setting the stage for immune dysregulation frequently seen in patients.

  • Submitted December 11, 2017.
  • Accepted April 30, 2018.