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Identifying the mechanisms through which calcineurin regulates proportional growth control.

Subject Area Developmental Biology
Evolutionary Cell and Developmental Biology (Zoology)
Cell Biology
Term from 2015 to 2021
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 283635409
 
Final Report Year 2022

Final Report Abstract

We identified that calcineurin regulated Kcnk5b activity by electrophysiological patch-clamp experiments and determined that transgenic Kcnk5b up-regulation in adult zebrafish fins led to the upregulation of shh, lef1 and adhl1a2 in the adult fin, but led to minimal up-regulation of pea3, an Fgf-responsive gene, or no up-regulation other members of the developmental program. Only chronic expression of Kcnk5b led to the up-regulation of these other genes. We found that transgenic up-regulation of Kcnk5b in zebrafish larva, also increased the expression of shh and lef1. From patch-clamp experiments, we found that serine 345 in the cytoplasmic C-terminal tail of Kcnk5b regulates Kcnk5b channel activity and that calcineurin no longer affected the channel when this serine is mutated; whereas, calcineurin still regulated the activity of the channel when other adjacent serines in its C-terminus were mutated and that mutations of these other serines had no effect on channel activity. We transferred these findings into transgenic experiments in vivo to show that mimicking post-translational modifications on serine 345 in the channel directly correlates with the increasing or decreasing the proportional growth of the entire adult fin. We set up in vitro Fluorescence Lifetime Microscopy to visualize the reduction of intracellular K+ when Kcnk5b was expressed in cells and used this in experiments of the eLIFE paper. The additional attribution of this method is because electrophysiological research has been hampered by the limitations on assessing the electrophysiology of cell and tissues in vivo. The important reason for setting up fluorescence lifetime microscopy is the translation of this application into a use with live zebrafish; consequently, we will provide a method to perform future electrophysiological studies in vivo.

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