Dissecting the functional interplay between the TOR pathway and the cilium in zebrafish.

ABSTRACT

The target-of-rapamycin (TOR) pathway is a major regulator of cellular growth, division, and metabolism by coupling growth and nutrient cues to fundamental processes such as translation and transcription. In vertebrate models, disruptions affecting components of the TOR pathway result in cilia size abnormalities and ciliopathic phenotypes such as renal cysts. However, the mechanism by which the TOR pathway influenced cilia length and function was unknown. Recent work from zebrafish, in conjunction with the green alga Chlamydomonas, demonstrates that TOR complex 1 (TORC1)-mediated cilia length control is achieved through translational regulation of ciliary precursors. Further, in zebrafish, aberrant TORC1 signaling leads to left-right asymmetric patterning defects due to inefficient ciliary motility and fluid flow generation in the Kupffer's vesicle, a conserved embryonic organ that establishes laterality. Together, such findings show the utility of a combinatorial zebrafish and Chlamydomonas approach to dissecting the mechanistic relationship between the cilium and signaling molecules such as TOR. Here, we describe tools, reagents, and methodologies for the manipulation of the TOR pathway and the analysis of cilia morphology and function in zebrafish and Chlamydomonas.