PhD Scientific Days 2023

KDP Poster session

Microscopic cartography – why making and reading maps during our excursions within the brain may be useful

Text of the abstract

Our research focuses on microglial cells, which are the main immune cells of the brain. Among other tasks, these cells play indispensable roles in maintaining brain homeostasis, assist the proper development of neurons, the formation and appropriate functioning of synaptic connections, regulate inflammatory processes, therefore they have a prominent role under both physiological and pathological conditions. However, the underlying communication pathways between microglia and neurons have so far not been satisfactorily understood.
Our research group recently discovered special contact sites between microglial processes and neuronal cell bodies, named somatic purinergic junctions. In both human and mouse brain tissue, microglial processes are connected to specialized communication islands on the cell bodies of neurons, which are characterized by the enrichment of proteins and cell organelles important in transcellular signaling.
We also aimed to understand, what changes can take place at these contacts from the embryonic period to old age. In this project, we first examined whether developing neurons also possess somatic junctions, which was achieved by correlated confocal laser-scanning microscope (CLSM) and immuno-electron microscopy. Using this correlative method, we verified that the putative contact sites visualized by diffraction-limited confocal microscopy are indeed direct connections, with nanometer-range proximity of microglial and neuronal plasma membranes.
In the other project, in vivo 2-photon microscopy was used to examine somatic junctions throughout the lifespan of mice. In order to return to the very same cells, we selected suitable areas in the cerebral cortex of 50-day-old mice, made detailed maps based on the location and shape of blood vessels, neurons and microglial cells, and took monthly measurements of exactly the same brain area. With this method, we have the opportunity to study changes of the same neuron-microglia assemblies longitudinally, over months.
During our work, we managed to bridge the resolution limits between light and electron microscopy by using the cartography of the selected brain areas, showing that developing neurons also possess direct somatic connections, and by erasing the time limits, we were able to observe the same connections in the brain over several months by in vivo 2-photon microscopy.