FZD4 (CD344) is a frizzled receptor that binds WNT-family proteins and plays a critical role in retinal vascularization and angiogenesis as well as maintenance of the blood brain barrier. FZD4 may be involved in transduction and intercellular transmission of polarity information during tissue morphogenesis and in differentiated tissues. It is also thought to function in the enteric nervous system, as it is found in neuronal and glial cells in gastrointestinal tissues in infants. In immunohistochemistry, FZD4 has cytoplasmic positivity in the brain, thyroid and adrenal glands, immune tissues, gastrointestinal tissues, the liver, the gallbladder, the pancreas, reproductive tissues, adipose tissues and skin. References: Stem Cells Int. 2016; 2016: 9076823, PMID: 26697080; Investigative Ophthalmology & Visual Science. 2011. Vol.52: 6452-6461, DOI:10.1167/iovs.10-7146;