Functional analysis of naturally occurring DCLRE1C mutations and correlation with the clinical phenotype of ARTEMIS deficiency.
BACKGROUND
The endonuclease ARTEMIS, which is encoded by the DCLRE1C gene, is a component of the nonhomologous end-joining pathway and participates in hairpin opening during the V(D)J recombination process and repair of a subset of DNA double-strand breaks. Patients with ARTEMIS deficiency usually present with severe combined immunodeficiency (SCID) and cellular radiosensitivity, but hypomorphic mutations can cause milder phenotypes (leaky SCID).


OBJECTIVE
We sought to correlate the functional effect of human DCLRE1C mutations on phenotypic presentation in patients with ARTEMIS deficiency.


METHODS
We studied the recombination and DNA repair activity of 41 human DCLRE1C mutations in Dclre1c(-/-) v-abl kinase-transformed pro-B cells retrovirally engineered with a construct that allows quantification of recombination activity by means of flow cytometry. For assessment of DNA repair efficacy, resolution of γH2AX accumulation was studied after ionizing radiation.


RESULTS
Low or absent activity was detected for mutations causing a typical SCID phenotype. Most of the patients with leaky SCID were compound heterozygous for 1 loss-of-function and 1 hypomorphic allele, with significant residual levels of recombination and DNA repair activity. Deletions disrupting the C-terminus result in truncated but partially functional proteins and are often associated with leaky SCID. Overexpression of hypomorphic mutants might improve the functional defect.


CONCLUSIONS
Correlation between the nature and location of DCLRE1C mutations, functional activity, and the clinical phenotype has been observed. Hypomorphic variants that have been reported in the general population can be disease causing if combined in trans with a loss-of-function allele. Therapeutic strategies aimed at inducing overexpression of hypomorphic alleles might be beneficial.
Division of Immunology, Boston Children's Hospital, Harvard Medical School, Boston, Mass.
Kerstin
K
Felgentreff
Division of Immunology, Boston Children's Hospital, Harvard Medical School, Boston, Mass.
Yu Nee
YN
Lee
Division of Immunology, Boston Children's Hospital, Harvard Medical School, Boston, Mass.
Francesco
F
Frugoni
Division of Immunology, Boston Children's Hospital, Harvard Medical School, Boston, Mass.
Likun
L
Du
Department of Immunology, Erasmus Medical Center, Rotterdam, The Netherlands.
Mirjam
M
van der Burg
Angelo Nocivelli Institute for Molecular Medicine, Department of Pediatrics, University of Brescia, Brescia, Italy.
Silvia
S
Giliani
Immunology Department, Ihsan Dogramaci Children's Hospital, Hacettepe University Medical School, Sıhhiye, Ankara, Turkey.
Ilhan
I
Tezcan
Department of Pediatric Immunology and Allergy, Necmettin Erbakan University, Meram Medical Faculty, Konya, Turkey.
Ismail
I
Reisli
CLIP-Childhood Leukemia Investigation Prague, Department of Pediatric Hematology and Oncology, 2nd Faculty of Medicine and University Hospital Motol, Charles University, Prague, Czech Republic.
Ester
E
Mejstrikova
Laboratory of "Genome Dynamics in the Immune System", INSERM UMR1163, Université Paris Descartes Sorbonne Paris Cité, Institut Imagine, Paris, France.
Jean-Pierre
JP
de Villartay
Department of Pathology and Immunology, Washington University School of Medicine, St Louis, Mo.
Barry P
BP
Sleckman
Department of Transfusion Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Mass.
John
J
Manis
Division of Immunology, Boston Children's Hospital, Harvard Medical School, Boston, Mass; Harvard Stem Cell Institute, Harvard University, Boston, Mass. Electronic address: Luigi.Notarangelo@childrens.harvard.edu.
Luigi D
LD
Notarangelo
D000293:Adolescent; D000328:Adult; D000483:Alleles; D001402:B-Lymphocytes / Q000502:physiology* / Q000528:radiation effects; D002461:Cell Line, Transformed; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins; D004720:Endonucleases; D006579:Heterozygote; D006657:Histones / Q000378:metabolism; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009154:Mutation / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D016374:Oncogene Proteins v-abl / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D011836:Radiation Tolerance / Q000235:genetics; D011839:Radiation, Ionizing; D016511:Severe Combined Immunodeficiency / Q000235:genetics*; D060152:V(D)J Recombination / Q000235:genetics; D055815:Young Adult
D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D009687:Nuclear Proteins; D016374:Oncogene Proteins v-abl; C426344:DCLRE1C protein, human; D004720:Endonucleases
ARTEMIS deficiency; DCLRE1C mutations; DNA repair; V(D)J recombination; nonhomologous end-joining; severe combined immunodeficiency