Generation of Irx1 knock-out zebrafish. Targeted gene mutation was performed by TALEN and CRISPR/Cas9 knockout methods for Irx1a (A) and for Irx1b gene (B), respectively. Frameshift mutation was caused by the knockout strategies. Insertion or deletion of the nucleotides was indicated by red letterings. (C) Three-day-old embryos of the zebrafish mutants. While either Irx1aor Irx1b homozygote mutants did not show abnormal morphology during embryonic development, some siblings (homozygote for both Irx1a and Irx1b) from the breeding of Irx1a^−/−/1b^+/− and Irx1a^+/−/1b^−/− showed severe morphologic abnormality. This suggests that majority of homozygote mutants of Irx1a and Irx1b are developmentally defective. A few of Irx1a^−/−/1b^−/− zebrafish, however, were found to survive up to 3 months of age but were not fertile and died within 6 months of age.

Expression of zebrafish Irx1 gene. (A) Whole mount ISH expression in embryogenic zebrafish. Irx1 gene expression is found highly in brain area at early developmental stage (see 48 hpf, hours postfertilizaton) and later distributed to internal organs (5 dpf, days postfertilization). (B-D) Images of ISH in 3-month-old adult tissue sections. (B) Expression in intestine and kidney. Both Irx1a and Irx1bgenes are expressed at the crypt base of intestines and renal tubular cells. (C) ISH observation of Irx1 gene expression in reproductive organs, typically in primordial germ cells and oocytes (insets indicate 40× low-power images). (D) Expression in the liver and bile ducts. While none of the hepatocytes express Irx1 gene, meticulous examination revealed obvious expression in the biliary tree including extrahepatic (arrows) and intrahepatic bile ducts (arrowheads).

ZFIN is incorporating published figure images and captions as part of an ongoing project. Figures from some publications have not yet been curated, or are not available for display because of copyright restrictions.

ZFIN is incorporating published figure images and captions as part of an ongoing project. Figures from some publications have not yet been curated, or are not available for display because of copyright restrictions.

ZFIN is incorporating published figure images and captions as part of an ongoing project. Figures from some publications have not yet been curated, or are not available for display because of copyright restrictions.