CONNEXIN43 IN NEONATAL EXCITATORY NEURONS IS IMPORTANT FOR MOTOR LEARNING

Abstract In the neocortex, gap junctions are expressed at very early developmental stages, and they are involved in many processes such as neurogenesis, neuronal migration and synapse formation. Connexin43 (Cx43), a gap junction protein, has been found to be abundantly expressed in radial glial cells, excitatory neurons and astrocytes. Although accumulating evidence suggests that Cx43-mediated gap-junctional coupling between astrocytes plays an important role in the central nervous system, the function of Cx43 in early excitatory neurons remains elusive. In this study, we knocked out Cx43 in the excitatory neurons with the Cre/loxP system to investigate the specific role(s) of early Cx43 expression in the regulation of behaviors. We crossed the Emx1-CreER mice with Cx43fl/fl mice to obtain Cx43 conditional knockout mice. Broad-spectrum behavioral tests, including assessments of emotionality (depression and anxiety), learning ability and motor capacity were applied to measure mouse behaviors. We performed tamoxifen injection around birth to remove Cx43 from excitatory neurons. Moreover, Western blot data suggest that Cx43 expression in neocortex were significantly reduced after deletion of Cx43 in neocortical excitatory neurons. Single-cell RT-PCR further confirmed the expression of Cx43 in neocortical excitatory neurons. The results from behavior tests showed that Cx43-cKO mice exhibited impaired short-term motor learning capacity. However, we did not detect a significant difference between Cx43- cKO and Cx43-WT mice in depression-related behaviors, anxiety-like behaviors, or memory capacity. These results suggested that Cx43 expression in excitatory neurons at early postnatal stages contributes to short-term motor learning capacity. References 1.Cotrina, M.L., Gao, Q., Lin, J.H.-C., Nedergaard, M. (2001) ‘Expression and function of astrocytic gap junctions in aging’ Brain Res, 901, 55–61. 2.Elias, L.A.B., Kriegstein, A.R. (2008) ‘Gap junctions: multifaceted regulators of embryonic cortical development’ Trends Neurosci, 31, 243–250. 3.Frisch, C., Theis, M., De Souza Silva, M.A., Dere, E., Sö hl, G., Teubner, B., Namestkova, K., Willecke, Ki., Huston, J.P. (2003) ‘Mice with astrocyte-directed inactivation of connexin43 exhibit increased exploratory behaviour, impaired motor capacities, and changes in brain acetylcholine levels’ Eur J Neurosci, 18, 2313–2318. 4.Su, X., Chen, J.-J., Liu, L.-Y., Huang, Q., Zhang, L.-Z., Li, X.-Y., He, X.-N., Lu, W., Sun, S., Li, H., Yu, Y.-C. (2017) ‘Neonatal CX26 removal impairs neocortical development and leads to elevated anxiety’ Proc Natl Acad Sci 114, 3228–3233.