Notch/Her12 signalling modulates, motile/immotile cilia ratio downstream of <i>Foxj1a</i> in zebrafish left-right organizer.

Abstract

Foxj1a is necessary and sufficient to specify motile cilia. Using transcriptional studies and slow-scan two-photon live imaging capable of identifying the number of motile and immotile cilia, we now established that the final number of motile cilia depends on Notch signalling (NS). We found that despite all left-right organizer (LRO) cells express <i>foxj1a</i> and the ciliary axonemes of these cells have dynein arms, some cilia remain immotile. We identified that this decision is taken early in development in the Kupffer's Vesicle (KV) precursors the readout being <i>her12</i> transcription. We demonstrate that overexpression of either <i>her12</i> or Notch intracellular domain (NICD) increases the number of immotile cilia at the expense of motile cilia, and leads to an accumulation of immotile cilia at the anterior half of the KV. This disrupts the normal fluid flow intensity and pattern, with consequent impact on <i>dand5</i> expression pattern and left-right (L-R) axis establishment.