A novel missense mutation in the nuclear factor-κB essential modulator (NEMO) gene resulting in impaired activation of the NF-κB pathway and a unique clinical phenotype presenting as MRSA subdural empyema.
BACKGROUND
We describe a previously unreported 437 T→G missense mutation producing a V146G substitution in the first coiled-coil (CC1) domain of nuclear factor-κB essential modulator (NEMO) in a 9-month-old boy with ectodermal dysplasia with immunodeficiency who presented with methicillin-resistant Staphylococcus aureus subdural empyema. We performed in vitro experiments to determine if this novel mutation resulted in impaired NF-κB signaling.


METHODS
IκBα phosphorylation experiments were performed using a Jurkat T cell line lacking endogenous NEMO expression that was transfected with vectors containing either the wild type or the patient's V146G mutation. The cells were stimulated with TNF-α to activate the NF-κB pathway. Phosphorylated IκBα was detected by immunoblotting with anti-phospho-IκBα antibodies. Peripheral blood mononuclear cells from the patient were stimulated with TNF-α or anti-CD3 and anti-CD28. Impaired IκBα degradation was detected using antibodies against the IκBα protein.


RESULTS
While TNF-α stimulation resulted in IκBα phosphorylation in NEMO-deficient Jurkat cells reconstituted with wild-type NEMO, cell transfected with the V146G mutant exhibited a 75% reduction in phospho-IκBα. Peripheral blood mononuclear cells from the patient showed impaired degradation of IκBα after stimulation when compared with normal controls.


CONCLUSIONS
The patient's V146G mutation results in impaired NF-κB activation in vitro. The mutation extends the known N-terminal boundary within the CC1 domain that produces an ectodermal dysplasia phenotype, and defines an infectious susceptibility previously unappreciated in ectodermal dysplasia with immunodeficiency (methicillin-resistant S. aureus subdural empyema), broadening the clinical spectrum associated with the disease.
Devora
Gene A
GA
Division of Allergy and Immunology, Department of Pediatrics and Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-8859, USA.
Sun
Lijun
L
Chen
Zhijian
Z
van Oers
Nicolai S C
NS
Hanson
Eric P
EP
Orange
Jordan S
JS
de la Morena
M Teresa
MT
D024881:Drug Resistance, Bacterial; D004476:Ectodermal Dysplasia; D013354:Empyema, Subdural / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism*; D007223:Infant; D019169:Jurkat Cells; D008297:Male; D008712:Methicillin / Q000627:therapeutic use; D050505:Mutant Proteins / Q000235:genetics; D020125:Mutation, Missense / Q000235:genetics; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013211:Staphylococcus aureus / Q000187:drug effects / Q000276:immunology* / Q000472:pathogenicity; D015533:Transcriptional Activation / Q000235:genetics; D019076:Transgenes / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism
C491731:IKBKG protein, human; D050505:Mutant Proteins; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D051550:I-kappa B Kinase; D008712:Methicillin