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.
