Immune dysregulation as a cause of autoinflammation in fragile X premutation carriers: link between FMRI CGG repeat number and decreased cytokine responses.
BACKGROUND
Increased rates of autoinflammatory and autoimmune disorders have been observed in female premutation carriers of CGG repeat expansion alleles of between 55-200 repeats in the fragile X mental retardation 1 (FMR1) gene. To determine whether an abnormal immune profile was present at a cellular level that may predispose female carriers to autoinflammatory conditions, we investigated dynamic cytokine production following stimulation of blood cells. In addition, splenocyte responses were examined in an FMR1 CGG knock-in mouse model of the fragile X premutation.


METHODS
Human monocyte and peripheral blood leukocytes (PBLs) were isolated from the blood of 36 female FMR1 premutation carriers and 15 age-matched controls. Cells were cultured with media alone, LPS or PHA. In the animal model, splenocytes were isolated from 32 CGG knock-in mice and 32 wild type littermates. Splenocytes were cultured with media alone or LPS or PMA/Ionomycin. Concentrations of cytokines (GM-CSF, IL-1β, IL-6, IL-10, IL-13, IL-17, IFNγ, TNFα, and MCP-1) were determined from the supernatants of cellular cultures via Luminex multiplex assay. Additionally, phenotypic cellular markers were assessed on cells isolated from human subjects via flow cytometry.


RESULTS
We found decreases in cytokine production in human premutation carriers as well as in the FMR1 knock-in mice when compared with controls. Levels of cytokines were found to be associated with CGG repeat length in both human and mouse. Furthermore, T cells from human premutation carriers showed decreases in cell surface markers of activation when compared with controls.


CONCLUSIONS
In this study, FMR1 CGG repeat expansions are associated with decreased immune responses and immune dysregulation in both humans and mice. Deficits in immune responses in female premutation carriers may lead to increased susceptibility to autoimmunity and further research is warranted to determine the link between FMR1 CGG repeat lengths and onset of autoinflammatory conditions.
Department of Medical Microbiology and Immunology, University of California Davis, Davis, California, United States of America; The M.I.N.D. Institute, University of California Davis, Davis, California, United States of America.
Milo
M
Careaga
Department of Medical Microbiology and Immunology, University of California Davis, Davis, California, United States of America; The M.I.N.D. Institute, University of California Davis, Davis, California, United States of America.
Destanie
D
Rose
The M.I.N.D. Institute, University of California Davis, Davis, California, United States of America; Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, California, United States of America.
Flora
F
Tassone
The M.I.N.D. Institute, University of California Davis, Davis, California, United States of America; Department of Neurological Surgery, University of California Davis, Davis, California, United States of America.
Robert F
RF
Berman
The M.I.N.D. Institute, University of California Davis, Davis, California, United States of America; Department of Pediatrics University of California Davis, Davis, California, United States of America.
Randi
R
Hagerman
Department of Medical Microbiology and Immunology, University of California Davis, Davis, California, United States of America; The M.I.N.D. Institute, University of California Davis, Davis, California, United States of America.
Paul
P
Ashwood
D000328:Adult; D000368:Aged; D000818:Animals; D016207:Cytokines / Q000096:biosynthesis / Q000378:metabolism*; D005260:Female; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics*; D005600:Fragile X Syndrome / Q000235:genetics* / Q000276:immunology*; D006579:Heterozygote; D006801:Humans; D007249:Inflammation / Q000276:immunology* / Q000473:pathology; D008214:Lymphocytes / Q000378:metabolism; D051379:Mice; D008875:Middle Aged; D009000:Monocytes / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D013154:Spleen / Q000378:metabolism; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*; D055815:Young Adult
D016207:Cytokines; D051860:Fragile X Messenger Ribonucleoprotein 1