Figure 2

Generation and phenotype of fndc3a^wue1/wue1 zebrafish mutants. (A) The CRISPR/Cas9 system was used to target exon 13 in the zebrafish fndc3a gene coding for the third fibronectin type III ___domain (nucleotides marked in light blue indicate sgRNA target sequence and in red the region of mutated sequence). (B) fndc3a^wue1/wue1 mutants showed straightened tail buds (22 hpf; n = 19/40), kinked tails (48 hpf; n = 27/100), and caudal fin deformations (120 hpf; n = 9/41) during the first days of embryonic development. (C) A fraction of adult fndc3a^wue1/wue1 mutants displayed weak (n = 15/71) to strong (n = 6/71) caudal fin phenotypes and tail malformations. (D) qPCR quantification of relative fndc3a expression levels in genotypic different groups of embryos indicated reduction of fndc3a transcripts in fndc3a^wue1/+ and fndc3a^wue1/wue1 (ΔΔCt calculation; significance levels of a 2-sided paired student t-test are given). Investigation of protein domains shown in A has been performed via the SMART database (Simple Modular Architecture Research Tool; http://smart.embl-heidelberg.de)⁶⁹. Black arrows indicate developmental malformations. Scale bars for whole embryos: 250 µm; scale bars for tail magnifications: 100 µm.