Pannexin 1 regulates dendritic protrusion dynamics in immature cortical neurons.

The integration of neurons into networks relies on the formation of dendritic spines. These specialized structures arise from dynamic filopodia-like dendritic protrusions. It was recently reported that cortical neurons lacking the channel protein pannexin 1 (PANX1) exhibited higher dendritic spine densities. Here, we expanded on those findings to investigate - at an earlier developmental timepoint (with more abundant dendritic protrusions) - whether differences in the properties of dendritic protrusion dynamics could contribute to this previously discovered phenomenon. Using a fluorescent membrane tag (mCherry-CD9-10) to visualize dendritic protrusions in developing neurons (at 10 days--, DIV10) we confirmed that lack of PANX1 led to higher protrusion density while transient transfection of leads to decreased protrusion density. To quantify the impact of PANX1 expression on protrusion formation, elimination, and motility, we used live cell imaging in DIV10 neurons (1 frame every 5 seconds for 10 minutes). We discovered that at DIV10, loss of PANX1 stabilized protrusions. Notably, re-expression of PANX1 in KO neurons resulted in a significant increase in protrusion motility and turnover. In summary, these new data revealed that PANX1 could regulate the development of dendritic spines, in part, by controlling dendritic protrusion dynamics. Dendritic spines are microscopic structures that allow for communication between brain cells. Previous work showed that knockout increases the density of dendritic spines, raising the possibility that PANX1 could regulate their formation and/or stability. To address this research question, here we studied the role of knockout and rescue on dendritic protrusions - the dynamic precursors of dendritic spines - in immature developing neurons. We found that knockout increased the density and stability of protrusions on developing neurons, and conversely, that PANX1-EGFP expression decreased protrusion density, and increased protrusion turnover and overall movement. These results enhance our understanding of PANX1 regulation of neuronal development and neuroplasticity.