Spatio-temporal visualisation and manipulation of endogenous Yap1 in medaka
A key requirement to address fundamental questions in developmental biology is the ability to visualise and manipulate endogenous signalling proteins in vivo. Here we generate such an enabling experimental tool for the highly conserved Hippo pathway and its transcriptional effector Yap1, which converts mechanical and chemical cues into transcriptional output during embryogenesis and regeneration. We generate and characterise a Yap1- mGreenLantern (Yap1-mGL) endogenous CRISPR/Cas9-mediated knock-in line that enables 4D analysis of Yap1 dynamics in medaka. We resolve Yap1- mGL expression and nuclear/cytoplasmic localisation in real time, revealing the onset of reporter fluorescence before gastrulation, tissue and cell-type specific Yap1-mGL localisation during somitogenesis and injury-induced Yap1 upregulation during larval spinal cord regeneration. Using the nanobody-based degron system, we degrade the Yap1 protein in vivo, recapitulating the genetic loss-of-function mutant phenotype. Combining endogenous tags with nanobody-based degrons offers a powerful approach to visualise and acutely perturb endogenous protein function in vivo.