Characterization of biklf / klf17 -deficient zebrafish in posterior lateral line neuromast and hatching gland development

Krüpple-like factors (Klfs) are highly conserved zinc-finger transcription factors that regulate various developmental processes, such as haematopoiesis and cardiovascular development. In zebrafish, transient knockdown analysis of biklf / klf17 using antisense morpholino suggests the involvement of biklf / klf17 in primitive erythropoiesis and hatching gland development; however, the continuous physiological importance of klf17 remains uncharacterized under the genetic ablation of the klf17 gene among vertebrates. We established the klf17 -disrupted zebrafish lines using the CRISPR/Cas9 technology and performed phenotypic analysis throughout early embryogenesis. We found that the klf17 -deficient embryos exhibited abnormal lateral line neuromast deposition, whereas the production of primitive erythrocytes and haemoglobin production were observed in the klf17 -deficient embryos. The expression of lateral line neuromast genes, klf17 and s100t , in the klf17 -deficient embryos was detected in posterior lateral line neuromasts abnormally positioned at short intervals. Furthermore, the klf17 -deficient embryos failed to hatch and died without hatching around 15 days post-fertilization (dpf), whereas the dechorionated klf17 -deficient embryos and wild-type embryos were alive at 15 dpf. The klf17 -deficient embryos abolished hatching gland cells and Ctsl1b protein expression, and eliminated the expression of polster and hatching gland marker genes, he1 . 1 , ctsl1b and cd63 . Thus, the klf17 gene plays important roles in posterior lateral line neuromast and hatching gland development.