IRF4 haploinsufficiency in a family with Whipple's disease.
Guérin A, Kerner G, Marr N, Markle JG, Fenollar F, Wong N, Boughorbel S, Avery DT, Ma CS, Bougarn S, Bouaziz M, Béziat V, Della Mina E, Oleaga-Quintas C, Lazarov T, Worley L, Nguyen T, Patin E, Deswarte C, Martinez-Barricarte R, Boucherit S, Ayral X, Edouard S, Boisson-Dupuis S, Rattina V, Bigio B, Vogt G, Geissmann F, Quintana-Murci L, Chaussabel D, Tangye SG, Raoult D, Abel L, Bustamante J, Casanova JL.
2019 Jul 1
Most humans are exposed to Tropheryma whipplei (Tw). Whipple's disease (WD) strikes only a small minority of individuals infected with Tw (<0.01%), whereas asymptomatic chronic carriage is more common (<25%). We studied a multiplex kindred, containing four WD patients and five healthy Tw chronic carriers. We hypothesized that WD displays autosomal dominant (AD) inheritance, with age-dependent incomplete penetrance. We identified a single very rare non-synonymous mutation in the four patients: the private R98W variant of IRF4, a transcription factor involved in immunity. The five Tw carriers were younger, and also heterozygous for R98W. We found that R98W was loss-of-function, modified the transcriptome of heterozygous leukocytes following Tw stimulation, and was not dominant-negative. We also found that only six of the other 153 known non-synonymous IRF4 variants were loss-of-function. Finally, we found that IRF4 had evolved under purifying selection. AD IRF4 deficiency can underlie WD by haploinsufficiency, with age-dependent incomplete penetrance.