E148Q MEFV mutation carriage and longevity in individuals of Ashkenazi origin

Pyrin variant E148Q potentiates inflammasome activation and the effect of pathogenic mutations in cis

OBJECTIVE

The p.E148Q variant in pyrin is present in different populations at a frequency of up to 29%, and has been associated with diseases, including vasculitis and FMF. The pathogenicity of p.E148Q in FMF is unclear, even when observed in cis or in trans to a single, typically recessive, pathogenic mutation. We performed functional validation to determine whether p.E148Q increases the ability of pyrin to form an active inflammasome complex in cell lines.

METHODS

We interrogated the Australian Autoinflammatory Disease RegistrY (AADRY) to find candidate inheritance patterns for the p.E148Q variant in pyrin. Different pyrin variant combinations were tested in HEK293T cells stably expressing the adaptor protein apoptosis-associated speck-like (ASC), which were analysed by flow cytometry to visualize inflammasome formation, with and without stimulation by Clostridioides difficile toxin B (TcdB). Inflammasome-dependent cytokine secretion was also quantified by ELISA of supernatants from THP-1 cells transduced with lentiviral expression vectors.

RESULTS

In AADRY, we observed the p.E148Q allele in individuals with autoinflammatory diseases alone or in conjunction with other pyrin variants. Two FMF families harboured the allele p.E148Q-M694I in cis with dominant heritability. In vitro, p.E148Q pyrin could spontaneously potentiate inflammasome formation, with increased IL-1β and IL-18 secretion. p.E148Q in cis to classical FMF mutations provided significant potentiation of inflammasome formation.

CONCLUSION

The p.E148Q variant in pyrin potentiates inflammasome activation in vitro. In cis, this effect is additive to known pathogenic FMF mutations. In some families, this increased effect could explain why FMF segregates as an apparently dominant disease.

Familial Mediterranean fever gene (MEFV) mutations and disease severity in systemic lupus erythematosus (SLE): implications for the role of the E148Q MEFV allele in inflammation

OBJECTIVE

Observed low prevalence of SLE among familial Mediterranean fever (FMF) patients in several large cohorts suggests a possible protective effect of the MEFV mutations from SLE. In contrast, SLE patient carriers for the common MEFV mutations had rather complex disease expression with an increased frequency of febrile episodes and pleurisy and a decreased renal complication rate. Our aim was to investigate the prevalence of MEFV gene mutations in patients with SLE and their effect on organ involvement in a well-defined group of biopsy-proven SLE nephritis patients.

MATERIAL AND METHOD

The prevalence of four MEFV gene mutations (M694V, M680I, V726A and E148Q) was investigated in 114 SLE patients and effect on disease severity was analyzed in patients with biopsy-proven SLE nephritis.

RESULTS

None of the SLE patients fulfilled the revised Tel-Hashomer criteria. Fourteen of 114 SLE patients (12.2%) were found to carry at least one MEFV mutation. A single patient in the SLE-Nephritis group was compound heterozygous for M694V/M680I mutations and only one patient in the SLE-Mild group was homozygous for E148Q mutation. Carrier frequency was similar to controls in SLE patients (12.2 vs 18.8%, p = 0.34). After the exclusion of the less penetrant E148Q mutation, re-analysis revealed an association between exon 10 mutations and SLE nephritis (p = 0.050, odds ratio (OR) = 4.16, 95% confidence interval (CI) = 1.04-16.6). Carrier rate for the E148Q mutation decreased in the SLE group (controls vs. SLE = 20/186 vs. 3/114, p = 0.08) and E148Q mutation was absent in SLE nephritis (controls vs. SLE nephritis = 20/186 vs. 0/47, p = 0.016, OR = 11.69, 95% CI = 0.69-197.13).

CONCLUSIONS

Carrier rate for the studied MEFV mutations was slightly lower in the SLE group, which is in agreement with previous observations that FMF may confer some protection from SLE. Exon 10 mutations were associated with SLE nephritis after the exclusion of the E148Q mutation. The significance of the E148Q as a disease-causing mutation is controversial, and whether E148Q substitution is a polymorphism generally affecting inflammatory pathways is not addressed in the current literature. In this regard, absence of the E148Q mutation in SLE nephritis may serve as a clue for further investigation into its role as a general modulatory polymorphism for inflammation. This clarification is necessary to conclude whether other more penetrant MEFV gene mutations confer susceptibility to nephritis in SLE.