The role of the homeobox gene Prox 1 in the regulation of betaB1-, betaA1/A3-, delta1, and alphaA- promoters was investigated in collaboration with Drs. M. Duncan (University of Delaware) and J. Piatigorsky (LMDB, NEI). Our data suggest that Prox 1 may act synergistically with Maf family members in regulation of betaB1-crystallin promoter. Prox 1 shows a dynamic nuclear:cytoplasmic distribution during the course of lens development. It is predominantly cytoplasmic in the lens placode as well as the lens epithelium. However, as lens epithelial cells begin to differentiate into the fibers, Prox 1 redistributes to the cell nuclei. Prox 1 antibody was used to study development and origin of the avian lymphatic system in collaboration with D. J. Wilting (Freiburg, Germany). We demonstrated that the lymphatic endothelium is derived from two sources: lymph sacs and mesenchymal lymphangioblasts. Prox 1 antibody was used to analyze distribution of lymphatic vessels in human liver cancer and cirrhosis in collaboration with Dr. R. Jain (Massachusetts General Hospital and Harvard Medical School). We showed that lymphatics are abundant in cirrhosis, but restricted to the tumor margin and surrounding liver in human hepatocellular carcinoma.