Changes in neuronal migration in neocortex of connexin43 null mutant mice

To identify a neural phenotype in connexin43 null mutant mice, electrophysiological properties, intercellular communication and neuronal migration were studied in the developing neocortex. In acute slice preparations from newborn mice, electrophysiological characteristics of cortical and hippocampal neurons were not significantly different between wild type and null mutant mice. However, gap junctional coupling as assessed by fluorescence recovery after photobleaching was significantly attenuated in neocortical brain slices of null mutant mice. To assess neuronal migration, dividing cells were labeled with bromodeoxyuridine (BrdU) on embryonic days 12, 14 and 16, respectively, corresponding to the period of cortical neurogenesis, and the neocortex examined 2 or 3 days after the labeling. BrdU-labeled cells were distributed in the neocortical wall with a significant change in the pattern in the neocortex of the null mutant, where labeled cells accumulated in the intermediate zone or in the inner part of the cortical plate. The result suggests a significant delay in neocortical neuronal migration in the connexin43 null mutants, and a possible role of connexin43 in this process through yet unidentified mechanisms.