Mutation of ZIC3 causes X-linked heterotaxy, a syndrome in which the laterality of internal organs is disrupted. Analysis of model organisms and gene expression during early development suggests ZIC3-related heterotaxy occurs due to defects at the earliest stage of left-right axis formation. Although there are data to support abnormalities of the node and cilia as underlying causes, it is unclear at the molecular level why loss of ZIC3 function causes such these defects. ZIC3 has putative roles in a number of developmental signalling pathways that have distinct roles in establishing the left-right axis. This complicates the understanding of the mechanistic basis of Zic3 in early development and left-right patterning. Here we summarise our current understanding of ZIC3 function and describe the potential role ZIC3 plays in important signalling pathways and their links to heterotaxy.
Keywords: Cilia; Gastrulation; Left-right patterning; Mutation; Node; Planar cell polarity.