Week 4: MAP(2)ing the way to progress–the antigens MAP2 and GFAP
Shriya S -
Hey everyone, welcome back to my blog! Unfortunately, it does take some time to capture the images of the immunohistochemistry (IHC) stains, so you won’t be seeing the IBA1 and GFAP stained tissue samples in this post. Two weeks ago, we conducted IHC to target the antigen GFAP, and this last week, we did the same for the antigen MAP2. I couldn’t talk about these antigens in the last post because I discussed the brain surgeries I had the opportunity of seeing. So, I will do that now!
GFAP
GFAP, or glial fibrillary acidic protein, is an antigen expressed by many cell types in the central nervous system, including astrocytes and ependymal cells–both two types of glial cells with many functions in the central nervous system including the biochemical control of endothelial cells that form the blood-brain barrier, provision of nutrients in nervous tissue, and production of cerebrospinal fluid (CSF). GFAP is thought to maintain astrocyte mechanical strength and the shape of cells. But, unfortunately, its exact function is not very well understood. Glial cells–cells in the nervous system that are not neurons–have so many functions that it’s hard to keep track of what proteins are contributing to what roles.
In addition to its many roles, GFAP has been shown to be important for healing after CNS injury, such as traumatic brain injury (TBI). Specifically, it plays an important role in the formation of glial scars–dense, fibrous tissue formed by astrocytes in response to a CNS injury. Scars in general are the body’s first healing response to an injury. Hence, glial scars act as a barrier to protect healthy neural tissue but also can impede proper axonal regeneration and healing (similar to how scar tissue feels harder and less flexible compared to your normal skin!).
MAP2
MAP2, or microtubule-associated protein 2, is another antigen found mainly on neurons, but also has been found on oligodendrocytes–a type of glial cell whose main function is to produce myelin sheath–insulating material around nerve fibers that fasten the signal. Generally MAP2 helps stabilize microtubules within the neuron and maintain neuronal structure. This makes sense since microtubules are essentially hollow tubes that are part of the cytoskeleton; their main role is to maintain the structural integrity of the cell. But, microtubules are also involved in cell division, so by connecting dots, one might say MAP2 also helps with cell division. However, this would be wrong since neurons and glial cells are fully differentiated cells–matured and specialized cells that have exited the cell cycle and thus, don’t divide.
After TBI, a subset of oligodendrocytes–oligodendrocyte progenitor cells–try to remyelinate cells whose axons and myelin sheaths were damaged, though this process is ineffective and the baseline of the brain before TBI is never achieved. Through IHC, by targeting MAP2 to see what changes oligodendrocytes undergo, one can better understand the role of oligodendrocytes post-TBI.
I hope this post taught you something new about two antigens in your body, both of which are heavily involved in neurotrauma research. Please don’t hesitate to ask questions about these antigens or their relevance in my research!
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