Résumé : Ectodermal dysplasia with immune deficiency (EDI) is an immunological and developmental disorder caused by alterations in the gene encoding NF-κB essential modulator (NEMO; also known as IκB kinase γ subunit [IKKγ]). Missense mutations in the gene encoding NEMO are associated with reduced signal-induced nuclear translocation of NF-κB proteins, resulting in defective expression of NF-κB target genes. Here, we report 2 unrelated male patients with EDI, both of whom have normal NEMO coding sequences, but exhibit a marked reduction in expression of full-length NEMO protein. TLR4 stimulation of APCs from these patients induced normal cytoplasmic activation and nuclear translocation of NF-κB. However, cells deficient in full-length NEMO were defective in expression of NF-κB-regulated cytokines, such as IL-12, suggesting a downstream defect in chromatin accessibility for NF-κB transcription factors. TLR4-stimulated APCs from the patients were defective in IKKα-dependent H3 histone phosphorylation at the IL-12 promoter and recruitment of NF-κB heterodimers RelA and cRel to the promoter. Expression of a super-active form of IKKα restored IL-12 production in a NEMO knockdown human monocytic cell line following LPS treatment. Our findings suggest that NEMO regulates the nuclear function of IKKα and offer new insights into the mechanisms underlying diminished NF-κB signaling in patients with EDI.