<prompt> In familial Mediterranean fever, the gene encoding the following protein undergoes mutation:PyrinPerforinAtrial natriuretic factorImmunoglobulin light chain  <response>: 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, Harrisons 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, Hursts The Hea, 13e. 