Novel Mutations in RASGRP1 are Associated with Immunodeficiency, Immune Dysregulation, and EBV-Induced Lymphoma
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RAS guanyl-releasing protein 1 (RASGRP1) deficiency has recently been shown to cause a primary immunodeficiency (PID) characterized by CD4+ T cell lymphopenia and Epstein-Barr virus (EBV)-associated B cell lymphoma. Our report of three novel patients widens the scope of RASGRP1 deficiency by providing new clinical and immunological insights on autoimmunity, immune cell development, and predisposition to lymphoproliferative disease.
One patient of Turkish origin (P1) and two Palestinian patients (P2, P3) were evaluated for immunodeficiency. To decipher the molecular cause of disease, whole exome sequencing was conducted. Identified mutations were validated by immunological and biochemical assays.
We report three patients presenting with similar clinical characteristics of immunodeficiency and EBV-associated lymphoproliferative disease. In addition, P2 and P3 exhibited overt autoimmune manifestations. Genetic screening identified two novel loss-of-function mutations in RASGRP1. Immunoblotting and active Ras pull-down assays confirmed perturbed ERK1/2 signaling and reduced Ras-GTPase activity in heterologous Jurkat cells with ectopic expression of RASGRP1 mutants. All three patients had CD4+ T cell lymphopenia. P2 and P3 showed decreased mitogen-induced lymphocyte proliferation, reduced T cell receptor excision circles, abnormal T cell receptor (TCR) Vβ repertoires, and increased frequencies of TCRγδ cells. TCR gamma repertoire diversity was significantly reduced with a remarkable clonal expansion.
RASGRP1 deficiency is associated with life-threatening immune dysregulation, severe autoimmune manifestations, and susceptibility to EBV-induced B cell malignancies. Early diagnosis is critical and hematopoietic stem cell transplantation might be considered as curative treatment.
KeywordsAutoimmunity EBV lymphoproliferation PID RASGRP1 T cell development
The authors thank the patients and their families for their collaboration and for their expert care by the interdisciplinary pediatric teams. The study would not have been possible without additional support by the German Academic Exchange Program (DAAD) and the Care-for-Rare Foundation.
I.S. and B.M. analyzed and interpreted results and I.S., B.M., and D.K. drafted the manuscript. B.M. designed, performed, and analyzed experiments for the patients. A.L., A.J.S., and E.R. performed the experiments for P2, P3. Y.L. and M.R. conducted NGS. S.H. analyzed NGS results. M.K., E.U., E.Y., T.P., and M.C. followed, diagnosed, and treated P1. R.S., T.S., V.V.D., and S.F. followed, diagnosed, and treated P2, P3. C.K., D.K., and R.S. designed and supervised the experiments.
This work was supported by grants from the Jeffrey Modell Foundation (JMF) (Raz Somech), the German Research Foundation (DFG CRC1054, Leibniz Program) (Christoph Klein, Daniel Kotlarz), and the Else Kröner–Fresenius-Stiftung (Christoph Klein). Daniel Kotlarz has been a scholar funded by the Daimler und Benz Stiftung, Reinhard-Frank Stiftung, and Else Kröner–Fresenius-Stiftung.
Compliance with Ethical Standards
All procedures were performed upon informed consent and assent from patients, first-degree relatives, and healthy donor controls in accordance with the ethical standards of the institutional and/or national research committees and with the current update of the Declaration of Helsinki.
Conflict of interest
The authors declare that they have no conflict of interest.
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