Clearance of cellular debris from the degenerating central nervous system (CNS) white matter is inefficient.
Debris accumulation, especially from myelin, precipitates maladaptive neuroinflammation which furthers disease
progression and prevents repair. Chronic white matter degeneration that produces cellular debris and protracted
innate immune inflammation is a hallmark of diverse disorders, including traumatic and ischemic CNS injury and
Multiple Sclerosis (MS). The development of therapies aimed enhancing debris clearance to promote repair is
thereby of broad translational relevance. Research aimed at uncovering central regulatory mechanisms
underlying the inflammatory response that facilitates debris clearance after white matter insult is therefore
prudent and necessary. The overarching objective of this research is to dissect molecular pathways of astrocyte-
microglia interaction that govern pro-restorative CNS innate immune responses to white matter degeneration.
The present research will investigate a newly identified mechanism of intercellular communication, through which
a distinct subpopulation of white matter degeneration-reactive astrocytes regulate microglia specification and
function required for the removal of inflammatory myelin debris and tissue repair. In Aim 1, we will use a
transgenic, cell type-specific loss-of-function system, single-nucleus RNA-Sequencing (snRNA-Seq) and mouse
models of acute and chronic white matter degeneration to assess the involvement of this unique astrocyte-
mediated signaling pathway in regulating damage-responsive microglia specification required for myelin debris
clearance and remyelination. In Aim 2, we will dissect the direct effects and receptor dependent mechanism of
action for a novel astrocyte-derived molecular cue on microglia molecular profile, motility, and capacity for myelin
debris phagocytosis using cultures of mouse primary and human iPSC-derived microglia. In Aim 3, we will
determine cell-intrinsic regulatory pathways underlying molecularly and functionally distinct states of white matter
astrocyte reactivity using cell-paired snRNA-Seq and single-nucleus Assay for Transposase-Accessible
Chromatin using Sequencing (snATAC-Seq), over time, in a mouse model of chronic white matter degeneration.
An integrative analysis pipeline will be used to generate gene regulatory programs of astrocyte reactivity,
including dynamic changes in chromatin structure and context-specific combinations of transcriptional regulators
(TR), which together govern genetic accessibility and distinct reactive changes in transcriptomic profile. Select
TR of molecularly distinct states of white matter astrocyte reactivity will be functionally interrogated in vivo by
loss-of-function studies. Together, this research will enhance the understanding of how astrocyte-microglia
interactions shape CNS innate immune responses that enable white matter repair. These data may also inform
new therapeutic avenues for harnessing restorative innate immune responses, involving astrocytes and
microglia, to prevent or attenuate maladaptive white matter inflammation, as well as improve outcome and
promote recovery after CNS injury and in disease.