Examining the establishment of cellular axes using intrinsic chirality.

T he establishment of asymmetry is no simple matter for the developing organism. How asymmetric differences are generated and maintained in tissues that still must coordinate with other developing tissues to form a correctly positioned, viable body plan is a central question in developmental biology. The ability to establish and maintain asymmetry is crucial to the development of many organisms. For example, asymmetric patterning along the left– right axis directs the development and placement of asymmetric organs in humans, including the heart. Defects in such patterning can cause congenital heart defects, many of which are fatal (1). Although the establishment of proper asymmetric patterning of the left–right axis is of critical importance, we still lack understanding of how it ultimately is achieved. In PNAS, Wan et al. (2) introduce insights concerning this complex developmental process by examining the establishment of cellular axes using intrinsic chirality.