Getting to the heart of planar cell polarity signaling

The genes that underpin normal heart development, and which can be disrupted to result in congenital structural malformations, are rapidly being uncovered. However, the specific cellular processes that lie downstream of these genetic cascades, accurately shaping tissues and complex structures within the heart, remain relatively unclear. The noncanonical Wnt planar cell polarity (PCP) signaling pathway is known to have a role in embryonic morphogenesis and as such is an important candidate pathway to carry out these roles in heart development. The pathway regulates the polarization of cells in a variety of contexts, allowing cells to change shape and position and to "know" their orientation within a mass of tissue. PCP signaling has also been shown recently to regulate the cellular position of the primary cilium. This organelle is known to be crucial for the establishment of left-right patterning in the early embryo and may also act as a signaling antenna for other developmental and regulatory pathways. It is not surprising that recent studies have also linked PCP to left-right patterning. In this review, we will examine the current evidence suggesting that PCP signaling has a central role in cardiac development and malformation.