Observing Neurodegeneration in Real Time Using 2-Photon Microscopy in the LSD1 Inducible Mouse Model

AD is characterized by two hallmark pathologies: the accumulation of pathological Aβ plaques and neurofibrillary tau tangles (NFTs). However, the role of NFTs in mediating neurodegeneration remains unclear. We have previously demonstrated that the H3K4 histone demethylase LSD1/KDM1A is mislocalized to cytoplasmic NFTs in AD cases. In agreement with this, we discovered that hippocampal deletion of LSD1 resulted in widespread loss of pyramidal neurons, a prominent feature of AD. Additionally, the neurodegeneration caused by loss of LSD1 is associated with AD-specific gene expression changes and learning and memory deficits, suggesting that the neurodegeneration in the LSD1 mouse model may be related to AD patients. In order to better understand neuronal cell death mechanisms, we propose using two-photon live imaging in the LSD1 inducible knockout mouse to visualize neurons dying in the cerebral cortex. To visualize neurons dying in the inducible LSD1 mouse model, we incorporated a Thy1-YFP neuronal reporter. Using a two-photon microscope, we will be able to visualize YFP-expressing neurons in an awake animal through a surgically implanted cranial window. Given the robust neurodegeneration phenotype, loss of LSD1 will generate a feasible and rapid timescale to view neurons degenerating in real time. Previously, we have shown that axons and dendrites are completely lost from hippocampal neurons in the LSD1 inducible knockout mice. Using live imaging, we hope to determine whether this is an active part of neuronal cell death in this model. In addition, the loss of LSD1 induces the inflammatory response, suggesting microglia may play a role in neurodegeneration. We will interrogate the role of the microglia activation in this system by modulating its function. Collectively, these studies will provide insight into how inhibition of the chromatin repressor LSD1 contributes to neurodegeneration, with the ultimate goal of generating novel therapeutic strategies targeting LSD1.