Mapping the grinch mutation. (a) Local genome assembly of the grinch locus using exon capture/BSA. The blue region marks the 10 cM gap in the meiotic map. The number of recombinants for each marker, calculated genetic distance and the location of the markers in v7.1 and v4.1 genome assemblies are shown. The 400 kb interval contains 2 genes: ccdc40 on the ends of scaffold 148 and 304 (v4.1) and ribosomal protein L38. (b) Schematic diagram of the protein sequences of the 21 mutant clones. Red regions indicate deletions, green box indicates insertions, and dashed lines indicate frameshifts. Number of bp inserted or deleted and translated amino acid (a.a.) length for each clone is indicated. See Additional file 1: Figure S5 for complete mutant protein and cDNA sequence. (c) Cilia-driven epidermal flow study using red microbeads. Arrows follow a particular bead’s trajectory through time. In left column, WT embryo shows equal flow on both the left and right sides. In middle column, grinch mutants show no flow on either side. In right column, mutants injected with WT ccdc40 mRNA and GFP tracer (insert) show rescue of flow on injected side. See Additional files 1– 4. Embryos in (c) are dorsal views with anterior to the right.