Figure 2

NF-κB immunolocalization during embryonic SMG development. A. Pseudoglandular Stage. B. Canalicular and Terminal Bud Stages. During embryonic mouse SMG development, the SMG primordium branches by repeated furcation at the distal ends of successive buds to produce a bush-like structure comprised of a network of elongated epithelial branches and terminal epithelial buds surrounded by loosely packed mesenchyme in the Pseudoglandular Stage. We evaluated the spatial distribution of NF-κB (p65) protein in the Pseudoglandular Stage (A) and demonstrated that NF-κB is diffusely distributed throughout the branching epithelia, and to a lesser degree, in the mesenchyme. As development continues, the SMG epithelia branches and buds hollow out by epithelial cell apoptosis during the Canalicular and Terminal Bud Stages to form the ductal system and presumptive acini. Because the embryonic SMG develops by repeated epithelial end bud branching, the morphogenetic state of terminal bud clusters differs between SMG regions, dependent on the time of branch formation. Thus both the Canalicular (double arrows) and the Terminal Bud (double arrowheads) Stages can be seen in B. In the Canalicular Stage (B, double arrows), NF-κB p65 is primarily immunodetected in the central region of the terminal buds. By contrast, NF-κB p65 is diffusely distributed in Early Terminal Bud Stage (B, double arrowheads) epithelia in terminal buds which exhibit lumina. Similar localization patterns were immunodetected for NF-κB p50 protein (not shown). Bar: 50 μm.