Sequence and expression analysis of cardiac ryanodine receptor 2 in broilers that died from sudden death syndrome

Sudden death syndrome (SDS) is a stress-related disease in broilers with no diagnostic clinical or necropsy findings. SDS is associated with ventricular tachycardia (VT) and ventricular fibrillation (VF); however, its pathogenesis is not precisely described at the molecular level. Dysfunction of ryanodine receptor 2 (RYR2), that controls rapid release of Ca2+ from the sarcoplasmic reticulum (SR) into the cytosol during muscle contraction, has been associated with VT and sudden cardiac death (SCD) in human patients with structurally normal heart, but there is no report describing abnormalities in RYR2 in diseased broilers. In order to advance our knowledge on the molecular mechanisms predisposing broilers to fatal arrhythmia, the present study was conducted to determine the occurrence of possible mutations and changes in the expression level of the chicken RYR2 gene (chRYR2) in broilers that died from SDS. An increase in mRNA expression level and nine novel point mutations in chRYR2 were found in relation to SDS. In conclusion, susceptibility to lethal cardiac arrhythmia in SDS may be associated with specific changes in intracellular Ca2+ cycling components such as RYR2 due to mutation and dysregulation. Finding the probable association of SDS with gene defects can be applied to select for chickens with lower susceptibility to SDS and decrease the poultry industry losses due to SDS mortality.