This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
In familial Mediterranean fever, the gene encoding the following protein undergoes mutation: 
Select and explain. 
A. Pyrin, B. Perforin, C. Atrial natriuretic factor, D. Immunoglobulin light chain
A: Pyrin
Answer: A: Pyrin 
Explanation: The familial Mediterranean fever gene encodes a 781-amino acid, 95 kDa protein, denoted pyrin (or marenostrin) that is expressed in granulocytes, eosinophils, monocytes, dendritic cells, and synol and peritoneal fibroblasts. Must know: ANP (Atrial Natriuretic peptide) is a 28-amino-acid peptide synthesized and released from atrial cardiomyocytes in response to stretch. ANP reduces vascular resistance while enhancing sodium excretion through extra renal and intrarenal mechanisms. Perforin is a cytolytic protein found in the granules of Cytotoxic T lymphocytes (CTLs) and NK cells. The immunoglobulin light chain is the small polypeptide subunit of an antibody (immunoglobulin). A typical antibody is composed of two immunoglobulin (Ig) heavy chains and two Ig light chains. Ref: Longo D.L., Fauci A.S., Kasper D.L., Hauser S.L., Jameson J.L., Loscalzo J. (2012). Chapter 330. Familial Mediterranean Fever and Other Hereditary Recurrent Fevers. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.;Hall J.E., Granger J.P., Jones D.W., Hall M.E. (2011). Chapter 69. Pathophysiology of Hypeension. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds), Hurst's The Hea, 13e.