Radiosensitive SCID patients with Artemis gene mutations show a complete B-cell differentiation arrest at the pre-B-cell receptor checkpoint in bone marrow.
Severe combined immunodeficiency disease (SCID) can be immunologically classified by the absence or presence of T, B, and natural killer (NK) cells. About 30% of T(-)B(-)NK(+) SCID patients carry mutations in the recombination activating genes (RAG). Some T(-)B(-)NK(+) SCID patients without RAG gene mutations are sensitive to ionizing radiation, and several of these radiosensitive (RS) SCID patients were recently shown to have large deletions or truncation mutations in the Artemis gene, implying a role for Artemis in DNA double-strand break (dsb) repair. We identified 5 RS-SCID patients without RAG gene mutations, 4 of them with Artemis gene mutations. One patient had a large genomic deletion, but the other 3 patients carried simple missense mutations in conserved amino acid residues in the SNM1 homology domain of the Artemis protein. Extrachromosomal V(D)J recombination assays showed normal and precise signal joint formation, but inefficient coding joint formation in fibroblasts of these patients, which could be complemented by the wild-type Artemis gene. The cells containing the missense mutations in the SNM1 homology domain had the same recombination phenotype as the cells with the large deletion, indicating that these amino acid residues are indispensable for Artemis function. Immunogenotyping and immunophenotyping of bone marrow samples of 2 RS-SCID patients showed the absence of complete V(H)-J(H) gene rearrangements and consequently a complete B-cell differentiation arrest at the pre-B-cell receptor checkpoint-that is, at the transition from CyIgmu(-) pre-B-I cells to CyIgmu(+) pre-B-II cells. The completeness of this arrest illustrates the importance of Artemis at this stage of lymphoid differentiation.
Noordzij
Jeroen G
JG
Department of Immunology, Erasmus MC/University Medical Center Rotterdam, The Netherlands.
Verkaik
Nicole S
NS
van der Burg
Mirjam
M
van Veelen
Lieneke R
LR
de Bruin-Versteeg
Sandra
S
Wiegant
Wouter
W
Vossen
Jaak M J J
JM
Weemaes
Corry M R
CM
de Groot
Ronald
R
Zdzienicka
Malgorzata Z
MZ
van Gent
Dik C
DC
van Dongen
Jacques J M
JJ
D017398:Alternative Splicing; D001402:B-Lymphocytes / Q000473:pathology*; D015153:Blotting, Western; D001853:Bone Marrow / Q000473:pathology*; D002454:Cell Differentiation / Q000235:genetics*; D004260:DNA Repair; D004268:DNA-Binding Proteins; D004720:Endonucleases; D005091:Exons; D005434:Flow Cytometry; D017353:Gene Deletion; D015321:Gene Rearrangement; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D008562:Membrane Glycoproteins; D009154:Mutation; D020125:Mutation, Missense; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction; D054420:Pre-B Cell Receptors; D011836:Radiation Tolerance; D011947:Receptors, Antigen, B-Cell; D016511:Severe Combined Immunodeficiency / Q000235:genetics* / Q000473:pathology; D014162:Transfection; D001618:beta-Lactamases / Q000235:genetics*
D004268:DNA-Binding Proteins; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D054420:Pre-B Cell Receptors; D011947:Receptors, Antigen, B-Cell; C426344:DCLRE1C protein, human; D004720:Endonucleases; D001618:beta-Lactamases