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Pkd2 affects the architecture of zebrafish left-right organizer
Ciliavolume 4, Article number: P84 (2015)
Dorsal anterior clustering (DAC) of motile cilia in the left-right organizer (LRO) is crucial for normal fluid flow dynamics and correct laterality in zebrafish . We directly demonstrated that charon/dand5 transcription is negatively regulated by strong flow in zebrafish LRO  which suggests that LRO cells have the ability to sense fluid flow and influence gene expression patterns, but how? Pkd2 ion channel is a good candidate because it participates in a mechanosensory complex that senses fluid flow and induces a calcium inward flux in kidney cells  and in nodal cells . In agreement, mouse and zebrafish mutants for Pkd2 have LR defects [4, 5]. However, Pkd2 is also involved in cell polarity during migration  and in extracellular matrix deposition  implying a role for Pkd2 in cell morphogenesis.
Determine whether Pkd2 knockdown affects DAC of ciliated LRO cells.
dnah7 morpholino  was injected to generate static cilia without affecting DAC . Each embryo was screened for static cilia by high-speed videomicroscopy. In parallel, Pkd2 knockdowns were imaged for flow dynamics followed by quantification of anterior / posterior cilia number through two-photon microscopy.
Pkd2 knockdown, contrary to Dnah7 knockdown, caused a remodelling in the LRO architecture by disrupting DAC. Moreover, Pkd2 knockdown resulted in abnormal fluid flow as a consequence of defective DAC.
Comparing Dnah7 and Pkd2 knockdowns we concluded that Pkd2 mediated pathway affects LRO morphogenesis by a mechanism that seems to be independent of its role in fluid flow mechanosensation. Meaning that Pkd2 triggers additional responses from those caused by LRO flow.
Supported by FCT-ANR/BEX-BID/0153/2012 grant.
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