Centriole enantiomerism: unexpected information from mice and fish

Abstract

In mice, asymmetry of internal organs is established by a left-ward fluid flow, produced by the innermost monociliated cells of the node and sensed by the immotile primary cilia of left peri-nodal cells; thus, the Nodal signaling pathway is asymmetrically (left-sided) expressed. However, right peri-nodal cells also, if excited by an artificial right-ward flow, break symmetry and activate the Nodal cascade, though inverting the asymmetry of visceral organs (situs inversus): peri-nodal cells prove to be adept at distinguishing flow directionality; moreover, the same signaling pathway is identically triggered in left and right peri-nodal cells, producing two symmetric architectural results: one program, two different implementations, one input, two mirror outputs. Recently, in the Kupffer’s vesicle (the laterality organ of zebrafish), chiral cilia orientation has been described: primary cilia, in left and right half, are mirror oriented relative to the midline. Do Kupffer’s vesicle histology and perinodal cell mirror behavior suggest primary cilia are enantiomeric organelles?