A zebrafish rbm24a-GFP knock-in line for monitoring lineage-specific dynamic protein expression and function

The RNA-binding protein Rbm24 is evolutionarily conserved, and its coding gene displays tissue-specific expression in vertebrates. However, the dynamic localization of this protein in different cell lineages remains elusive. We have generated a zebrafish rbm24a-GFP knock-in line in which endogenous Rbm24a is tagged with GFP, allowing the precise monitoring and systematic characterization of its spatiotemporal expression and subcellular localization during development and in the adult. Rbm24a-GFP not only shows strongly restricted expression in a subset of tissues, but also displays cell type- and stage-specific subcellular localization patterns. The protein mainly localizes in the cytoplasm of lens fiber cells and progenitors of sensory hair cells. It undergoes dynamic cytoplasm to nucleus translocation during differentiation of myoblasts and cardiomyoblasts. We further examined the effectiveness of this knock-in line for inhibiting Rbm24a function. Targeted degradation of Rbm24a-GFP using the zGrad system produces phenotypes of zygotic rbm24a mutants or morphants, with defective heart morphogenesis and disrupted cardiac muscle integrity. Therefore, this line will be particularly useful for understanding Rbm24a-GFP dynamic expression and localization changes under homeostasis and pathological conditions. It also enriches the resource of zebrafish knock-in line and provides a convenient tool for functional study of the protein through degron-mediated conditional degradation.