A, Representative photomicrographs of AVC explants incubated with HAPLN1-targeted siRNA. B-E, Candidate gene expression in HH16 chick embryos was knocked down with siRNA in an in vitro collagen gel assay. The mean number of cells in the collagen gel was determined and normalized to the number of cells in controls (100%). Con - GC-content matched, randomized siRNA constructs with no homology to any known chick gene, TGFβR3 - siRNA targeting a gene known to be required for EMT in vitro. a or b - independent constructs targeting indicated gene. * - p<0.01. F, Transcriptional network depicting genes known to be downstream of NF-κB which had increased expression in the AVC and VEN. See legend in Figure 4. G, NF-κB inhibition by two independent small molecule inhibitors (10 μM BMS 345541 and 2 μM SN50) resulted in a loss of function an in vitro collagen gel assay. SB431542, an ALK5 kinase inhibitor, was used as a positive control. Vehicle - 0.01% DMSO. * - p<0.01.