Defective development of the gall bladder and cystic duct in Lgr4‐ hypomorphic mice

Leucine‐rich repeat (LRR) ‐containing G protein coupled receptor (LGR) family members are characterized by the presence of a seven‐transmembrane domain and LRR motifs. We describe a new function for Lgr4 in the development of the gall bladder and cystic duct and in the epithelium–mesenchyme interaction. Lgr4 expression was observed in the gall bladder epithelium when the gall bladder primordium elongated ventrally. Although Lgr4 hypomorphic mutant (Lgr4^Gt/Gt) embryos developed a normal gall bladder bud at embryonic day (E) 10.25, no further elongation was observed at later stages. At E12.5, the mesenchyme surrounding the gall bladder had completely disappeared in Lgr4^Gt/Gt embryos, while the gall bladder remained unelongated. Neighboring tissues such as liver and pancreas were unaffected, as revealed by expression of marker genes. This is the first report of a mutant mouse that lacks a gall bladder and cystic duct without affecting the other tissues that derive from the same hepatic diverticulum. Developmental Dynamics 238:993–1000, 2009. © 2009 Wiley‐Liss, Inc.