Caspases and apoptosis in fish

Apoptosis has a vital impact on the development and homeostasis of all multicellular organisms. Hence, all metazoan species seem to possess the necessary components of the apoptotic machinery, but in general, their numbers and complexity have increased during evolution. The key apoptotic factors are a cascade of cysteine proteases known as caspases. The fish homologous of almost all the mammalian caspases have also been identified, but several fish-specific caspases with putative distinct functions have also been reported. Despite these differences, the extrinsic and intrinsic pathways have been remarkably well conserved throughout 500 million years of vertebrate evolution. Here, the authors review what is currently known about fish caspases and apoptosis and demonstrate the huge amount of sequence information available from a range of fish species by screening Atlantic salmon genome databases for apoptotic homologous.