Background/Purpose: Familial Mediterranean fever (FMF) is thought to be inherited as an autosomal recessive trait. However, there are frequent deviations from this model. The aim of this study was to explore epigenetic modifications in patients with FMF.

Methods: Ten patients diagnosed with FMF according to the Tel-Hashomer criteria were recruited from the rheumatology outpatient clinic of Sheba Medical Center, Tel Hashomer, Israel. All patients were homozygous for the M694V mutation, the most common mutation in FMF, and all had the most severe phenotype of the disease. All were in the quiescent phase at the time of the study. Total RNA was drawn from peripheral blood and profiled for microRNA expression using NanoString nCounter technology. Findings were compared to 10 healthy age- and sex-matched control subjects. Statistical analyses were conducted using R software, version 3.2. Data preprocessing and normalization followed by differential expression analysis were performed using the R package DESeq2 (25516281) and in house scripts. A priori P values were adjusted for false discovery rate (FDR).

Results: Of the 798 mature human miRNAs probed, 103 exhibited reasonable expression levels in these cells. Seven were found to be significantly deregulated in the patients with FMF: three were significantly downregulated compared to control samples (miR-107, let−7d−5p, and miR-148b-3p), and four were significantly upregulated (miR-144-3p, miR-21−5p, miR−4454 and miR-451a), all with an adjusted P value of  <0.01 (Figure 1).

To ensure that the observed changes were true biological effects and not technical artifacts, we performed Taqman quantitative real time polymerase chain reaction (qRT-PCR) analysis of two of the differentially expressed miRNAs between the patients and controls. Each miRNA was quantified in each sample, and its expression level was normalized to the reference RNA, U6-snRNA. In both groups, the direction of effect and the miRNA expression patterns in the NanoString analysis were consistent with the Taqman measurements (R²=0.93)

Conclusion: We identified significant epigenetic changes in patients with clinically quiescent FMF. Further research is warranted in order to elucidate critical FMF manifestation such as susceptibility to early disease, disease severity, risk of the development of amyloidosis, and resistance to colchicine. All these factors might be ultimately explained, at least in part, by epigenetic modifications.

Figure 1