The Relationships Between Mutations In B30.2Domain Of MEFV Gene And The Risks Of Ankylosing Spondylitis In Chinese Population

BackgroundAnkylosing spondylitis (AS) is a kind of rheumatoid factor-negative, chronic, progressive inflammatorydisease which initially involves the sacroiliac joints, violate the axial joints, and get ligaments andtendon inflamed in the attachment points of bone. It also can affect internal organs and otherorganizations and has been thought a complex and multi-gene genetic disease. According to statisticalresults，different genetic background and environment will affect the risk of AS. In china, prevalencerate of AS is0.3%, but in Europe, especially in mid-Europe, this data is from0.1%to1.4%. Moreover,the morbidity of AS is from0.5/100000to14/100000in a year. Until now, the diagnosis of AS has beenimproved. However, treatment strategies have little improvement. Familial Mediterranean Fever (FMF)is an autosomal recessive genetic disorder, and main characteristic is affected by periodic fever underself-inflammation which may lead to peritonitis, pleuritis, arthritis and secondary amyloidosis whichmay make person died. Because the main populations affected are in the Mediterranean Coast, thisdisease is called FMF. In1997, MEFV for FMF had been cloned and identified in13.3of human16pchromosome. Mutations of MEFV are considered as the cause of FMF. Inflammation and ossificationare two main features of AS. And, the inflammation will lead to the ossification. FMF is an autoimmunedisease, and inflammation is the main characteristic. The common characteristic of AS and FMF isinflammation, and the person with AS and FMF had been reported in public data. The protein of MEFVis called Pyrin with a Pyrin domain and781AA which locates in cytoskeleton. Pyrin can directly bind toPro-caspase-1and inhibitor of nuclear factor-κB (NF-κB) kinase complex which play key role ininflammation and cell apoptosis. Pyin also can bind interleukin-1β (IL-1β)å'ŒNF-κB pathway to controlinflammation and cell apoptosis. B30.2domain is located in the C terminal of Pyrin, with~200AA, andplays role in protein-protein interactions.~50-60AA in B30.2domain is the key sequence in which themain mutations of FMF are located. In this study, this sequence target is in this domain. BecauseMEFV is an important regulator for innate immunity, it may play a key role in development of AS.ObjectiveTo discuss the relationship between MEFV’s mutations in B30.2domain and the risk of AS, andestablish the correlation between mutations and its clinical findings. At last, to build a prediction model to explain the effect of mutations on clinical findingsMethodBlood DNA of100AS and200controls selected from113AS and400controls who join this planswere extracted and purified. Using the primer6.0, the primers were designed to amplify the targetfragment of DNA. Then3730XL was used to sequence the products of PCR. Using DNA sequencing toobtain mutations of MEFV, we can get the relationship between these mutations and AS. Then wefound the correlation between mutations and its clinical findings. At last, combining moleculardynamics with structural biology, our group evaluated the effects of mutations of MEFV on Stability ofPyrin and built a prediction model to explain the effect of mutations on clinical findings with data ofmolecular biology.ResultsIn this study, we collected the blood and clinical findings of100AS and200controls to evaluate theeffects of mutations in B30.2domain of MEFV on AS. Rs61752717(M694V)，rs28940579(V726A)，rs146720938(N733S) and rs104895171(S749C) are four missense mutations which affect the risk ofAS (P<0.05). M694V has significant association with ESR(X2=8.082P=0.004)å'ŒCRP(X2=15.297P=0.000) in analyzing the clinical findings. This result suggests the M694V has important effect onPyrin. We used molecular dynamics with structural biology to simulate MEFV’s mutations whichchange the energy and of stability of Pyrin. Rs61752717(M694V)， rs104859201(V722M)，rs28940579(V726A) and rs140434276(I729V) can make the most large change the energy and ofstability of Pyrin. rs61752717(M694V)å'Œrs28940579(V726A) are the risk mutations of AS. Thedocking data of Pyrin and Caspase1provides that M694V plays key role in interactions between twoproteins. When M changes V in694point，interactions between two proteins become weak and thecatalytic activity of Caspase1is improved. more，31-kDa IL-1B with no activity will transform to17-kDa IL-1B with activity. This result will improve the inflammation. So this prediction model canexplain clinical findings.ConclusionOur study discuss the relationship between point mutations in B30.2domain of MEFV and risk of ASand clinical findings. To explain the associations between M694V and ESR and CRP, a prediction model was built to analysis point mutations on Pyrin. However, this finding need to be identified in alarge sample, and the mechanism of this process should be found.