Evolution of the Heart from Bacteria to Man

Evolution of the Heart from Bacteria to Man -- BISHOPRIC 1047 (1): 13 -- Annals of the New York Academy of Sciences: "Evolution of the Heart from Bacteria to Man
NANETTE H. BISHOPRIC

This review provides an overview of the evolutionary path to the mammalian heart from the beginnings of life (about four billion years ago ) to the present. Essential tools for cellular homeostasis and for extracting and burning energy are still in use and essentially unchanged since the appearance of the eukaryotes. The primitive coelom, characteristic of early multicellular organisms (800 million years ago), is lined by endoderm and is a passive receptacle for gas exchange, feeding, and sexual reproduction. The cells around this structure express genes homologous to NKX2.5/tinman, and gradual specialization of this 'gastroderm' results in the appearance of mesoderm in the phylum Bilateria, which will produce the first primitive cardiac myocytes. Investment of the coelom by these mesodermal cells forms a 'gastrovascular' structure. Further evolution of this structure in the bilaterian branches Ecdysoa (Drosophila) and Deuterostoma (amphioxus) culminate in a peristaltic tubular heart, without valves, without blood vessels or blood, but featuring a single layer of contracting mesoderm. The appearance of Chordata and subsequently the vertebrates is accompanied by a rapid structural diversification of this primitive li"/.../