Generation of zebrafish ltk, alk, and augmentor loss-of-function mutants. (A) Schematic representation of augmentor ligands and sequence alignment of the augmentor domain (AugD) of human and zebrafish augmentors. “Zfin” indicates the sequence as given in the Zfin database, and “Exp” indicates the experimental and observed sequence of aug-α1. In all other zebrafish augmentors, the observed sequence matches the Zfin database. Color coding depicts the conservation of different protein domains in zebrafish and human: red, signal peptide (SP); orange, N-terminal variable region; brown, augmentor domain. Red arrowheads indicate CRISPR/Cas9 cut sites within the respective DNA-coding sequences. “AUG” indicates human orthologs, and “Aug” indicates zebrafish orthologs, as per convention. (B) Schematic representation of receptor and ligand protein domains in human and zebrafish. Color coding depicts the conservation of different protein domains in zebrafish and human: cyan, N-terminal region; green, MAM domain; yellow, LDLa repeat; black, EGF-like motif; purple, tyrosine kinase domain (KD). Proteins are not to scale. Red arrows indicate CRISPR/Cas9 cut sites within the respective DNA coding sequences. ALK and LTK indicate human orthologs; Alk and Ltk indicate zebrafish orthologs, as per convention (C) Lateral view (magnification: 27×) of whole-mount zebrafish embryos genotyped as indicated. (D) qPCR analysis of the indicated transcripts for the respective genotypes (n = 3–5; error bars indicate SEM).