Analysis of TNFRSF1A Gene R92Q Mutation in Familial Mediterranean Fever

This study examines the frequency of TNFRSF1A gene R92Q mutation in patients with Familial Mediterranean Fever (FMF) and the role of this mutation in FMF. The study included 223 FMF patients with definite diagnosis, according to Tel-Hashomer criteria, carrying two mutations and 205 FMF patients as controls (symptomatically diagnosed) with definite diagnosis but without any of the MEFV gene mutations screened. The DNA samples of FMF patients and controls were genotyped with regard to TNFRSF1A gene R92Q mutation by PCR–RFLP method. Genotypes and allele frequencies of the TNFRSF1A gene R92Q mutation were similar in the two groups (p=0.481 and p=0.48, respectively). Because of the similarities between the symptoms of FMF and TNFRSF1A-associated periodic syndrome (TRAPS), the frequencies of the TNFRSF1A gene R92Q mutation was studied in patients with two MEFV gene mutations and also in patients without any of the twelve most common MEFV gene mutations. No significant difference was observed between the two groups. Despite sharing common symptoms, it seems that FMF is not confused with TRAPS as the TNFRSF1A gene R92Q mutation frequencies are similar between both groups. Address for correspondence: Melek Yuce OndokuzMayis University Faculty of Medicine Department of Medical Biology 55139, Samsun/Turkey Telephone: +90 5055406127 Fax: +90 (362) 457 60 91 E-mail: [email protected] INTRODUCTION Hereditary Periodic Fever Syndromes (HPFS) are a group of diseases including Familial Mediterranean Fever (FMF), tumor necrosis factor receptor-associated periodic syndrome (TRAPS), cryopyrin-associated periodic syndromes (CAPSs), pyogenic arthritis, pyodermagangrenosum and acne (PAPA) syndrome, pediatric granulomatous arthritis, hyperimmunoglobulinemia D with periodic fever syndrome (HIDS), chronic recurrent multifocal osteomyelitis (CRMO), deficiency of the IL-1 receptor antagonist (DIRA), and deficiency of the IL-10 receptor early-onset enterocolitis (IBD) (Henderson and Goldbach 2010). These monogenic diseases of the innate immune system are characterized with self-limited inflammatory attacks, and they are called autoinflammatory syndromes (Grateau and Duruoz 2010). Although autoinflammatory diseases have some common clinical features such as fever attacks, serous membrane inflammation, muscle-skeleton system involvement, various types of rashes and amyloidosis, they also show different characteristics such as age of onset, duration and type of treatment (Stjernberg-Salmela et al. 2004). Familial Mediterranean Fever (FMF, OMIM #249100) is the most common inherited periodic fever syndrome, which is characterized by recurrent attacks of fever accompanied with peritonitis, pleuritis, arthritis, and a typical rash called erysipelas-like erythema. Severity of the disease results from the association of FMF with the formation of AA amyloidosis (Sohar et al. 1967). However, the introduction of colchicine treatment in the early 1970s changed the natural history of the disease (Zemer et al. 1974), completely abolishing the attacks in 60% of the patients, substantially decreasing them in 35%, and preventing the appearance of amyloidosis in almost all of them. Approximately 5% of the patients do not respond to colchicine despite the use of maximal doses (Pras and Kastner 1997). Although there are cases, such as the three Japanese patients recently reported by Fukushima et al. (2014), of autosomal dominant inheritance, FMF generally has an autosomal recessive inheritance and affects populations of the Mediterranean basin such as Sephardic Jews, Armenians, Turks and Arabs. FMF has also been identified in European populations (Booth et al. 144 MELEK YUCE AND HASAN BAGCI 1998). MEFV gene which causes Familial Mediterranean Fever is located on the short arm of chromosome 16. Up to date, 296 different sequence variants have been reported in the MEFV gene (Milhavet et al. 2008). A novel missense mutation (I247V) was recently reported from Hatay Province of Turkey (Gunesacar et al. 2014). Encoded by this gene, pyrin/marenostrin protein, which consists of 781 amino acids regulates the production of mature interleukin-1 (IL1) and is also involved in the pathogenesis of various autoinflammatory diseases (Yagel et al. 2010). It is believed that this protein plays an “auto regulator” role on leukocytes. Pyrin is expressed particularly in leukocytes, monocytes and to some extent in fibroblasts. Normally, an association is believed to exist between this protein and some cytokines that have important roles in inflammation and signal molecules responsible for apoptosis such as NF-KB. As in familial Mediterranean fever, if there is a mutation in MEFV gene, the formation of IL-1ß, which is an important factor in inflammation, will be stimulated and also apoptosis will be suppressed and thus, increased inflammatory response will arise as a result of minor stimulations (Kasapçopur and Arisoy 2006). The diagnosis of FMF has long been made based only on clinical criteria. Cloning of the FMF gene (MEFV) and the identification of the mutations that causes the disease have increased hopes on quicker and more accurate diagnosis of FMF (The International FMF Consortium 1997). However, since molecular diagnosis does not have sufficient sensitivity, even after sequencing of all the genes, a definitive diagnosis of FMF can result in failure in some of the typical patients. Because of the changeable nature of the disease and because it is characterized by an age dependent penetrance, it can be extremely hard to make FMF diagnosis in the presence of typical findings, especially in the absence of family history and in the case of a late onset. Several sets of diagnostic criteria have been proposed, with their validity evaluated and compared with each other (Berkun and Eisenstein 2014). However, a definitive diagnosis enables the use of colchicine, which is an effective treatment in preventing amyloidosis and attacks, in suitable daily doses and for a life time (Zemer et al. 1986). The tumor necrosis factor receptor associated periodic syndrome (TRAPS, OMIM # 142680) was initially reported in Irish and Scottish families (Williamson et al. 1982), but is now known to be more common than previously thought (Yagel et al. 2010). TRAPS, the most common autosomal dominant autoinflammatory disease (Rigante et al. 2014), is caused by mutations in the TNFRSF1A gene on chromosome 12 and encodes the 55-kD tumor necrosis factor (TNF)-alpha receptor 1 (TNFR1), which consists of 445 amino acids (McDermott et al. 1999). TNF- is the major inflammatory cytokine which induces the synthesis of other inflammatory cytokines such as interleukin-1 (IL-1) and interleukin-6 (IL-6), activates leukocytes, increases the expression of adhesion molecules and regulates apoptosis while providing host defense against intracellular pathogens together with inflammation management (Karatay and Melikoglu 2007). TRAPS is characterized by fever, abdominal pain, erythematous skin rash, muscle pain, conjunctivitis, irregular attacks of periorbital edema and amyloidosis. However, clinical findings differ (Hull et al. 2002). Similar to FMF, physical stress or trauma stimulates the attacks. Diagnosis is usually made by the analysis of mutations in the gene TNFRSF1 (Kasapçopur and Arisoy 2006). Because of the variability of the clinical findings, genetic confirmation is required for diagnosis. TRAPS patients may show different clinical manifestations as several mutations have been found in association with the disease (Cosan et al. 2013; Rigante et al. 2014). Treatment of TRAPS with non-steroidal antiinflammatory (NSAI) drugs, etanercept which is a TNF- blocker, and anakinra which is an IL-1 receptor antagonist, was found to be effective in most patients (Karatay and Melikoglu 2007; Yagel et al. 2010; Rigante et al. 2014). Presently, 138 different sequence variants have been reported in the TNFRSF1A gene (Milhavet et al. 2008). However, the R92Q substitution is the most frequent and widespread mutation identified in patients suffering from TRAPS. Carriers of this genetic defect show milder and more heterogeneous symptoms (Kauffman et al. 2012). Rationale and Aim of the Study When the FMF patients who applied to this laboratory were examined, it was found that some patients who had definitive diagnosis according to Tel-Hashomer criteria and who carried ANALYSIS OF TNFRSF1A GENE R92Q MUTATION 145 FMF clinical characteristics did not carry any of the screened MEFV gene mutations. Since the clinical characteristics of TRAPS and FMF are similar, the aim of this study was to analyze TNFRSF1A gene R92Q mutation in FMF patients. MATERIAL AND METHODS