IKBKG (NEMO) 5' Untranslated Splice Mutations Lead to Severe, Chronic Disseminated Mycobacterial Infections

Abstract

Four patients with adult-onset, disseminated mycobacterial infection had 5' UTR mutations in IKBKG without clear physical stigmata of NEMO deficiency. These mutations caused decreased levels of NEMO protein and Toll-like receptor driven cytokine production. Three patients died from disseminated disease. These mutations may be missed by whole exome sequencing.

Figure 1.

A, B.II.1 Mycobacteria⁺ macular erythematous plaques on back and neck. B, Genomic (upper) and cDNA (lower) structure of IKBKG. Consensus splice sequence shown on genomic structure above (wild-type) and below (patients). cDNAs from wild-type (upper) and patients (lower) showing 110 base deletion (dotted line). C, IKBKG transcript levels in PBMCs from A.I.1, B.II.1, B.II.3, normalized to the housekeeping gene, TBP, which encodes the TATA-box binding protein, and compared to blood-bank controls. D, NEMO staining in PBMCs from B.II.1 and B.II.3 compared to blood-bank controls. Blue - isotype, red - NEMO specific antibody. Number indicates fluorescence index. E, PBMC cytokine production from blood-bank controls (HC, n = 81) and patients A.I.1 (average of 3 separate assays) and B.II.1 (1 assay). Cells were cultured for 48 hours with TLR agonists and supernatants were collected. Average cytokine production levels were log₁₀ transformed and data entered into HeatMapper [12]. Top 2 rows are IL12p70 production in response to PHA and IFNγ production in response to PHA+IL12. The remaining rows are clustered by measured cytokine (listed between horizontal bars). The stimuli are listed on the left of the figure and the analyte on the right. Abbreviations: GM-CSF, granulocyte-macrophage colony-stimulating factor; IFNγ, interferon γ; IL, interleukin; PBMC, peripheral blood mononuclear cell; NEMO, nuclear factor κB essential modulator; PHA, phytohemagglutinin; TNF, tumor necrosis factor α; TLR, Toll-like receptor.