Loss of ARHGEF1 causes a human primary antibody deficiency
Amine Bouafia, … , Eric Oksenhendler, Sven Kracker
Amine Bouafia, … , Eric Oksenhendler, Sven Kracker
Published December 6, 2018
Citation Information: J Clin Invest. 2019;129(3):1047-1060. https://doi.org/10.1172/JCI120572.
View: Text | PDF
Research Article Immunology

Loss of ARHGEF1 causes a human primary antibody deficiency

Abstract

ARHGEF1 is a RhoA-specific guanine nucleotide exchange factor expressed in hematopoietic cells. We used whole-exome sequencing to identify compound heterozygous mutations in ARHGEF1, resulting in the loss of ARHGEF1 protein expression in 2 primary antibody–deficient siblings presenting with recurrent severe respiratory tract infections and bronchiectasis. Both ARHGEF1-deficient patients showed an abnormal B cell immunophenotype, with a deficiency in marginal zone and memory B cells and an increased frequency of transitional B cells. Furthermore, the patients’ blood contained immature myeloid cells. Analysis of a mediastinal lymph node from one patient highlighted the small size of the germinal centers and an abnormally high plasma cell content. On the molecular level, T and B lymphocytes from both patients displayed low RhoA activity and low steady-state actin polymerization (even after stimulation of lysophospholipid receptors). As a consequence of disturbed regulation of the RhoA downstream target Rho-associated kinase I/II (ROCK), the patients’ lymphocytes failed to efficiently restrain AKT phosphorylation. Enforced ARHGEF1 expression or drug-induced activation of RhoA in the patients’ cells corrected the impaired actin polymerization and AKT regulation. Our results indicate that ARHGEF1 activity in human lymphocytes is involved in controlling actin cytoskeleton dynamics, restraining PI3K/AKT signaling, and confining B lymphocytes and myelocytes within their dedicated functional environment.

Authors

Amine Bouafia, Sébastien Lofek, Julie Bruneau, Loïc Chentout, Hicham Lamrini, Amélie Trinquand, Marie-Céline Deau, Lucie Heurtier, Véronique Meignin, Capucine Picard, Elizabeth Macintyre, Olivier Alibeu, Marc Bras, Thierry Jo Molina, Marina Cavazzana, Isabelle André-Schmutz, Anne Durandy, Alain Fischer, Eric Oksenhendler, Sven Kracker

×

Figure 6

ARHGEF1-deficient lymphocytes exhibit impaired motility.

Options: View larger image (or click on image) Download as PowerPoint
ARHGEF1-deficient lymphocytes exhibit impaired motility. (A) SDF1-direct...
(A) SDF1-directed chemotaxis (Boyden chambers) analysis of PBMCs from patients (P1, n = 2; P2, n = 2) and healthy donors (n = 4). The migration index was defined as ratio of the number of migrating cells from the patient sample divided by the number of migrating cells from the healthy donor sample. *P < 0.05, 1-sample, 2-tailed t test on ratio. (B) Effects of fibronectin (Fn) coating on the passive migration of T cell blasts from healthy donors (n = 2) and patients (P1, n = 1; P2, n = 1). (C) Representative photographs showing the displacement of patient and healthy donor T cell blasts. Live cell imaging was performed during a minimum of 3 hours with photographs acquired every 50 seconds. Cropped areas are depicted here, and complete videos are available as Supplemental Videos 1–3. Stars show uropod anchoring and detachment point. Original magnification, ×20. (D) Dot plot showing the mean displacement of healthy donor and patient T cell blasts determined by live cell imaging as described in C. ****P < 0.0001, 2-tailed Welch’s t test on log2-transformed data. (E) Dot plot of the measure of the length of cell’s tails at the maximum of their elongation. *P < 0.05; **P < 0.01, 2-tailed Welch’s t test on log2-transformed data. For D and E, each symbol represents a single cell measurement. Measurements were performed with T cell blasts from independent healthy donors (circle;s n = 3), P1 (squares; n = 1), and P2 (triangles; n = 2).