These Hhexflox/flox mutant mice possess loxP sites flanking exons 2-3 of the hematopoietically expressed homeobox (Hhex) gene. HHEX is a transcription factor required for production of all lymphoid lineages and for early development of the liver. Expression is seen in the ventral foregut endoderm at E8.5 and in hepatobiliary tissue during later stages of development. HHEX expression is also evident in adult liver in hepatocytes and biliary epithelial cells in the intrahepatic bile ducts. Mice that are homozygous for this allele are viable and fertile. When bred to mice that express tissue-specific Cre recombinase, resulting offspring will have exons 2-3 deleted in the cre-expressing tissues.
For example, when bred to mice expressing Cre Recombinase in the hepatic diverticulum, resulting offspring were embryonic lethal and had small and cystic livers, absent gall bladders and extrahepatic bile ducts.
When bred to mice expressing Cre Recombinase in the embryonic liver, resulting mice exhibited irregular development of intrahepatic bile ducts, cystic biliary epithelial cells, and a slow, progressive form of polycystic liver disease in adult mice.
