Gain Deeper Insights into Cellular Connectivity with ZEISS Dynamics Profiler

Connexin proteins form gap junctions that directly connect astrocytes and oligodendrocytes into a cellular network. Neurons also connect via a different set of connexins but do not connect to astrocytes except in some rare developmental stages and brain regions. A major astrocyte connexin 43 (Cx43, GJA1) is highly expressed in the brain and most other organs; Cx43 mutations in humans produce skeletal malformations, white matter abnormalities, and highly variable cognitive deficits. Loss of oligodendrocyte Cx47 in humans leads to the variable but severe demyelinating brain disorder called Pelizaeus-Merzbacher Like Disease. Changes in gap junction expression and subcellular localization have been reported in humans and mouse models of brain diseases including major depression, autism spectrum disorder, traumatic brain injury, multiple sclerosis, Alzheimer’s disease, and many others. Clearly astrocyte gap junctions are important in human brain health and should be better understood.

Along with other labs, we have used high-resolution light microscopy to study the dynamics of gap junction supramolecular complexes and their protein binding partners. We used super-resolution confocal microscopy and Fluorescence Recovery After Photobleach (FRAP), respectively, to study the structure and dynamics of gap junctions. These imaging tools allowed new insights into the molecular mechanisms underlying gap junction nexus structure and dynamics. Most of the experiments to test these new ideas were performed with gap junctions of exaggerated scale and in non-neural cell lines because measuring the movement of Cx43 channels and their binding partners in the relevant small cellular spaces/scales exhibited by astrocytes in brain tissue (less than five micrometers in diameter) is challenging or impossible with FRAP or other techniques used to quantify protein mobility. Therefore, we are now using ZEISS Microscopy’s exciting new extended fluorescence correlation spectroscopy tool called Dynamics Profiler to quantify the number and mobility of proteins that interact with gap junctions in several distinct cellular compartments of micrometer scales. We will show unpublished data on the directionality of Cx43 interacting proteins changes at boundaries in the gap junction nexus supramolecular complex. More accurate understanding of protein dynamics at the molecular scale will be essential to building and interpreting computational models of astrocyte contributions to brain activity in health and disease.