CELL-TYPE-SPECIFIC NUCLEAR TRANSLOCATION OF FIBROBLAST GROWTH FACTOR-II ISOFORMS DURING CHICKEN KIDNEY AND LIMB MORPHOGENESIS

Analysis of the fibroblast growth factor-2 (FGF-2 or bFGF) proteins du ring chicken embryonic pattern formation and organogenesis revealed th at three isoforms (18.5, 20.0, and 21.5 kDa) were synthesized by alter native translation initiation from one coding region. A highly specifi c antiserum was raised and used for studying the temporal and spatial distribution of the FGF-2 isoforms during chicken embryogenesis. The d istribution of FGF-2 proteins during limb pattern formation has been u nraveled. Their presence in both ectodermal and mesenchymal cells is c onsistent with an involvement in regulating the balance of growth and differentiation. High levels of FGF-2 proteins were furthermore detect ed in all epithelial cells of the developing kidney from the pronephri c stage onward. The proteins were in general predominantly cytoplasmic , but a specific subpopulation of limb mesenchymal cells and kidney ep ithelial cells (podocytes) showed a striking nuclear localization. Nuc lear translocation of the FGF-2 proteins occurred in differentiating p odocytes of meso- and metanephric glomeruli and was maintained in adul t kidneys. These results, in contrast to previous in vitro studies, re vealed that nuclear accumulation of FGF-2 proteins is restricted to fe w specific cells during embryogenesis. (C) 1994 Academic Press, Inc.