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Fig. 2
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).