Immune deficiency caused by impaired expression of nuclear factor-κB essential modifier (NEMO) because of a mutation in the 5′ untranslated region of the NEMO gene

Background: Nuclear factor-κB (NF-κB) is a key transcription factor that regulates both innate and adaptive immunity as well as ectodermal development. Mutations in the coding region of the IκB kinase γ/NF-κB essential modifier (NEMO) gene cause X-linked ectodermal dysplasia with immunodeficiency. Objective: To determine the genetic cause of recurrent sinopulmonary infections and dysgammaglobulinemia in a patient with a normal NEMO coding sequence and his affected brother. Methods: TNF-α and IFN-α production in response to Toll-like receptor (TLR) stimulation was analyzed by ELISA, NEMO mRNA levels were measured by quantitative PCR, and NEMO protein expression was measured by Western blotting. NF-κB activation was assessed by nuclear translocation of p65 and luciferase reporter gene assays. Results: TLR-induced TNF-α and IFN-α production by PBMCs was impaired in the patient and his brother. Sequencing of the patient's NEMO gene revealed a novel mutation in the 5′ untranslated region, which was also present in the brother, resulting in abnormally spliced transcripts and a 4-fold reduction in mRNA levels. NEMO protein levels in EBV transformed B cells and fibroblasts from the index patient were 8-fold lower than normal controls. NF-κB p65 nuclear translocation in the patient's EBV B cells after TLR7 ligation was defective. NF-κB-dependent luciferase gene expression in IL-1-stimulated fibroblasts from the patient was impaired. Conclusion: This is the first description of immune deficiency resulting from low expression of a normal NEMO protein.