Broadening horizons: new links between cilia and heart development and disease

Congenital heart disease (CHD) is the most common birth defect, and its pathogenesis is closely related to the abnormal establishment of the left-right (LR) bod<i>y</i> axis, which highly depends on the ciliary function of the left-right organizer (LRO). This review systematically expounds the molecular pathways by which ciliary structural and functional abnormalities cause cardiac malformations by integrating multi-species model evidence. We believe that defects in multiple conserved genes (including <i>CFAP45</i>, <i>ZIC3</i>, <i>FOXJ1</i>, <i>NEK3</i>, <i>APLNR</i>, and microRNAs) disrupt ciliary assembly, motility, or signaling capacity, leading to the disappearance of the leftward nodal flow or mechanical sensing failure within the LRO. This further interrupts the left-specific calcium ion flicker and the activation of the Nodal-Pitx2 signaling cascade, ultimately resulting in failed cardiac looping and structural defects (such as ventricular septal defect and transposition of the great arteries). This review integrates transcriptional regulation, protein stability, miRNA-mediated fine regulation, and the planar cell polarity (PCP) pathway into a unified "cilia-LRO-heart" network and explores the molecular mechanisms of cilia in valve diseases and cardiac fibrosis. This not only deepens the understanding of the fundamental biological processes of heart development but also provides new molecular targets and theoretical frameworks for the genetic diagnosis and counseling of related congenital heart diseases.