miRNAs in Cardiac Development

This chapter aims to summarize the available data on regulation of cardiac development and stem cell differentiation by miRNAs. Heart malformations occur in as high as 1% of newborns, presenting a significant clinical problem in our modern world. The first functional organ in the embryo is the heart and cardiovascular system and the heart is susceptible to congenital defects more than any other organ. Both intrinsic and extrinsic factors determine the development of the cardiovascular system. miRNA was initially described as being fundamental for developmental biology first in nematode worms and then in phylogenically more advanced organisms. Many defects of the miRNA machinery are incompatible with correct and/or continued development. On the other hand, pluripotency and cellular differentiation are intricate biological processes that are coordinately regulated by a complex set of factors and epigenetic regulators. As in other tissues, a distinct set of miRNAs is specifically expressed in pluripotent embryonic stem cells. This chapter describes the involvement of miRNAs in normal cardiac development, in congenital heart disease and Down syndrome, and in determining stem cell fate. In particular, the roles of miR-1, miR-133, miR-130a and miR-138 in cardiac development are described as these miRNAs have been experimentally studied in detail.