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.