Polymorphism identification and cardiac gene expression analysis of the calsequestrin 2 gene in broiler chickens with sudden death syndrome

1. Sudden death syndrome (SDS) in broilers is a cardiac disease associated with ventricular tachycardia (VT) and ventricular fibrillation (VF); however, its pathogenesis at the molecular level is not precisely determined. 2. Downregulation and mutations of calsequestrin 2 (CASQ2), a major intracellular Ca2+ buffer, have been associated with VT and sudden cardiac death (SCD) in humans but in chickens there is no report describing CASQ2 abnormalities in cardiac diseases. 3. In order to better understand the molecular mechanisms predisposing the myocardium to fatal arrhythmia in broilers, the mRNA expression level of chicken CASQ2 gene (chCASQ2) in the left ventricle of dead broilers with SDS was determined and compared to healthy broilers using quantitative real-time PCR (qPCR). To determine the probable mutations in chCASQ2, PCR and direct sequencing were also done. 4. Results showed a reduction in chCASQ2 expression in broilers dead by SDS. Three novel mutations (K289R, P308S, D310H) which are absent in healthy broilers were observed in chCASQ2. 5. It is concluded that susceptibility to fatal cardiac arrhythmia in SDS may be associated with changes in intracellular Ca2+ balance due to mutation and downregulation of chCASQ2.