Mammalian cardiac morphogenesis involves a number of fundamental processes, which are as yet poorly understood at the molecular level, such as the commitment of mesodermic cells to cardiogenic cells, the fusion of cardiogenic mesoderm into a tubular heart, the rightward looping of the tubular heart, the formation of valves and septa, the chamber specification, the trabeculation of myocardium, the vasculogenesis, etc. The resulting cardiovascular system comprises a diversity of cell types, which need to work in concert to generate normal cardiovascular function. Among those are muscle cells critical for producing and maintaining pulsatile flow, neuroendocrine cells involved in control and regulation, endothelial cells lining the vascular tree and matrix secretory cells responsible for the deposition and upkeep of fibrous and elastic components of the system. Genes with a spatial and/or temporal pattern of expression during heart development are anticipated to play an important role in the formation of a functioning heart. Thus, the primary objective of our project is to generate a comprehensive catalogue of genes expressed during development of the rat heart, and to conduct microarray hybridisation experiments to identify a subset of spatially and/or temporally regulated genes. Our ultimate goal is to contribute resources that might facilitate research aimed at understanding the molecular mechanisms underlying heart development and congenital heart diseases. To date we have generated a rat heart UniGene set comprising 5,000 unique 3′ESTs from a total of 11,900 3′ESTs derived from a number of non-normalised and normalised adult and embryonic heart cDNA libraries. More specifically, ESTs were generated from cDNA libraries made from adult heart, 13 dpc ventricles, 15 dpc atria, 15 dpc ventricles, 15 dpc AV canal, 17 dpc atria, 17 dpc ventricles and 17 dpc AV canal. Microarray hybridisation will be performed with cDNA targets derived from RNA obtained from each region of the heart throughout development for identification of spatially and/or temporally regulated genes.