Delta-catenin is a protein that was believed to be neuron specific but spoiler alert it is in astrocytes as well! In the catinen-cadherin complex, delta-catenin is important in cell adhesion by cadherins between pre and post synaptic neurons. Literature on delta-catenin has shown that it can coordinate changes in perisynaptic processes (Arikkath, J., et al). Recently delta-catenin was discovered in astrocytes posing the question of whether it is important for neuron-astrocyte interactions by the same or similar mechanism?
Astrocytes are a type of glial cell that regulates neural functions. Astrocyte morphogenesis is correlated with synaptogenesis or the uptake and removal of synapses (Strogsdill, J.A., et al). Astrocyte release factors have been shown to affect synaptic processes such as glutamate uptake and ion homeostasis. I am working on answering the question of whether direct interaction between astrocytes and neurons affects astrocyte morphogenesis or, in other words, astrocyte complexity?
CTNND2 is the gene that encodes delta-catenin in both neurons and astrocytes. Over-expression in astrocytes results in stickier astrocytes with more adhesions and less complexity. This summer I am working on experiments to knockdown CTNND2 and then test the effects on cell adhesion. One set of tests involves entering a mRNA knockdown of CTNND2 into astrocytes alone to see the resulting effects on astrocyte morphology compared with wild type astrocytes. Preliminary results have showed a decrease in astrocyte complexity which supports my hypothesis. Knocking down CTNND2 in neuron culture will also provide insights. My project is to run a series of combination co culture experiments: wild type astrocytes with CTNND2 knockdown neurons, CTNND2 knockdown astrocytes with wild type neurons, and CTNND2 knockdown astrocytes with CTNND2 knockdown neurons. These permutations will provide some data on the importance of cadherin and delta-catenin in cell interactions.
The next set of experiments I am working on are done in order to image the effects of knocking down CTNND2 in the brain of mice. With a technique called Post Natal Astrocyte Labeling by Electroporation (PALE) astrocytes can be visualized with a confocal microscope to analyze their complexity. One experiment is to genetically introduce a flox into the genome to knockdown CTNND2 mice. This allows for the researcher to choose which cells they don’t want to express the floxed gene. Another aspect of the project is to knockdown the gene in the anterior cingulate cortex (ACC) of the brain which is associated with autonomic processes as well as attention, decision making, and other thinking processes. The ACC is linked to autism in several ways, so visualizing the function of delta-catenin in astrocyte morphology in this region could provide some insight into how the mutation of certain genes leads to cognitive abnormalities. This project fits within the larger goal of the lab which is to understand the interactions of cells in the brain. How cells pass information back and forth is the first small step in understanding how people retain information, make decisions, and have such complex cognitive abilities.