A hypomorphic R229Q Rag2 mouse mutant recapitulates human Omenn syndrome.
Rag enzymes are the main players in V(D)J recombination, the process responsible for rearrangement of TCR and Ig genes. Hypomorphic Rag mutations in humans, which maintain partial V(D)J activity, cause a peculiar SCID associated with autoimmune-like manifestations, Omenn syndrome (OS). Although a deficient ability to sustain thymopoiesis and to produce a diverse T and B cell repertoire explains the increased susceptibility to severe infections, the molecular and cellular mechanisms underlying the spectrum of clinical and immunological features of OS remain poorly defined. In order to better define the molecular and cellular pathophysiology of OS, we generated a knockin murine model carrying the Rag2 R229Q mutation previously described in several patients with OS and leaky forms of SCID. These Rag2(R229Q/R229Q) mice showed oligoclonal T cells, absence of circulating B cells, and peripheral eosinophilia. In addition, activated T cells infiltrated gut and skin, causing diarrhea, alopecia, and, in some cases, severe erythrodermia. These findings were associated with reduced thymic expression of Aire and markedly reduced numbers of naturally occurring Tregs and NKT lymphocytes. In conclusion, Rag2(R229Q/R229Q) mice mimicked most symptoms of human OS; our findings support the notion that impaired immune tolerance and defective immune regulation are involved in the pathophysiology of OS.
Marrella
Veronica
V
Human Genome Department, Istituto di Tecnologie Biomediche, CNR, Via Fratelli Cervi 93, Segrate, Milan 20090, Italy.
Poliani
Pietro Luigi
PL
Casati
Anna
A
Rucci
Francesca
F
Frascoli
Laura
L
Gougeon
Marie-Lise
ML
Lemercier
Brigitte
B
Bosticardo
Marita
M
Ravanini
Maria
M
Battaglia
Manuela
M
Roncarolo
Maria Grazia
MG
Cavazzana-Calvo
Marina
M
Facchetti
Fabio
F
Notarangelo
Luigi D
LD
Vezzoni
Paolo
P
Grassi
Fabio
F
Villa
Anna
A
D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D001120:Arginine / Q000235:genetics; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics*; D004195:Disease Models, Animal; D030342:Genetic Diseases, Inborn / Q000235:genetics / Q000276:immunology* / Q000503:physiopathology; D005973:Glutamine / Q000235:genetics; D006801:Humans; D007108:Immune Tolerance / Q000235:genetics; D007153:Immunologic Deficiency Syndromes / Q000235:genetics* / Q000503:physiopathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed
D004268:DNA-Binding Proteins; C499308:Rag2 protein, mouse; D005973:Glutamine; D001120:Arginine