Microglia-specific loss of PU.1 function rescues neurodegenerative phenotypes in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by progressive decline of cognitive ability. An important component of AD, and other chronic neurodegenerative diseases, is generation of an innate inflammatory response within the CNS, characterized by activation of microglia, the resident immune cells of the brain. Transcription factor PU.1 has been known to play an important role in myeloid and lymphoid cell development, however its function in microglia and how it contributes to disease pathology is not well understood. Using transcriptional and chromatin state profiles during AD-like pathology in the CK-p25 mouse model of neurodegeneration, we showed that PU.1 specifically targets noncoding regions which regulate expression changes of immune response genes during AD, suggesting it may act as master regulator of microglia activation. Here, we examine the role of PU.1 in neurodegeneration by using a conditional knockout (cKO) cassette (Cx3cr1CreER+/-) to inducibly deplete PU.1 from microglia in the CK-p25 mouse model of neurodegeneration. We found that knocking out PU.1 rescues multiple neurodegenerative phenotypes. Specifically, PU.1 inhibition reduces neurodegeneration-specific increase in microglia cell number, improves neuronal survival and reverses functional synaptic plasticity deficits in the hippocampus of the CK-p25 mouse. Overall design: Profiling genome-wide changes in PU.1 binding by ChIP-seq in the hippocampus of a mouse model of neurodegeneration and PU.1-dependent changes in gene expression by RNA-Seq in mouse hippocampal FAC-sorted microglia