CRISPR-mediated Labeling of Cells in Chick Embryos Based on Selectively Expressed Genes

The abilities to mark and manipulate specific cell types are essential for an increasing number of functional, structural, molecular, and developmental analyses in model organisms. In a few species, this can be accomplished by germline transgenesis; in other species, other methods are needed to selectively label somatic cells based on the genes that they express. Here, we describe a method for CRISPR-based somatic integration of reporters or Cre recombinase into specific genes in the chick genome, followed by visualization of cells in the retina and midbrain. Loci are chosen based on an RNA-seq-based cell atlas. Reporters can be soluble to visualize the morphology of individual cells or appended to the encoded protein to assess subcellular localization. We call the method eCHIKIN for electroporation- and CRISPR-mediated Homology-instructed Knock-IN.