The primary focus of our research is to understand the role of microglia in neural circuit development and plasticity in the healthy and diseased nervous system. We are particularly interested in:

1) How do microglia respond to changes in neural activity and, in turn, modulate synaptic connectivity?  
2)  Is microglial dysfunction at synapses an underlying cause of neurological disease?
3) How do microglia modulate other glial and vascular cell types within the nervous system to affect brain development?

To address these questions, the lab has developed cutting-edge molecular genetic approaches combined with high resolution static and 2-photon live imaging. Major lines of research include:

1.     Dissecting the molecular mechanisms underlying microglia-synapse interactions

Microglia interact and modulate synaptic connectivity but the underlying mechanisms are just beginning to be deciphered. Projects in the lab are designed to identify molecular mechanisms that modulate microglia-synapse interactions. These projects combine cutting-edge RNAseq, screens in Drosophila, and novel in vitro and in vivo approaches in rodents to dissect new mechanisms regulating microglia function at synapses throughout the lifespan of the animal. Ultimately, we are ablating genes of interest in vivo specifically in microglia and assessing changes in synapses as well as overall behavior.

Microglia (green) and retinal ganglion cell presynaptic inputs labeled by anterograde tracing with cholera toxin β subunit conjugated to Alexa 594 (CTB-594, purple) in the juvenile mouse lateral geniculate nucleus (LGN, P30).

Microglia (green) and retinal ganglion cell presynaptic inputs labeled by anterograde tracing with cholera toxin β subunit conjugated to Alexa 594 (CTB-594, purple) in the juvenile mouse lateral geniculate nucleus (LGN, P30).

2.     Investigating microglial responses to changes in sensory experience

Sensory experience is known to drive synapse remodeling throughout the CNS. We are now using the rodent barrel cortex and visual systems to understand how microglia respond to changes in sensory experience and, in turn, determine how these responses affect the neural circuit. We are measuring experience-dependent microglial responses on a molecular level using cell-specific RNAseq and genetic dissection of genes in vivo and in vitro. 

 
A)  Whiskers are removed in P4 mice.  B)  Within 6 days post deprivation, there is a significant decrease in layer IV thalamocortical presynaptic terminal density in the barrel cortex corresponding to the deprived whiskers compared to spared whiskers (control).  C)  Microglia engulf thalamocortical presynaptic inputs within 24 hours of deprivation.

A) Whiskers are removed in P4 mice. B) Within 6 days post deprivation, there is a significant decrease in layer IV thalamocortical presynaptic terminal density in the barrel cortex corresponding to the deprived whiskers compared to spared whiskers (control). C) Microglia engulf thalamocortical presynaptic inputs within 24 hours of deprivation.

 

To visualize responses on a cellular level, we have developed strategies to simultaneously visualize glial cells and specific synaptic circuits known to undergo experience-dependent remodeling by static high resolution imaging as well as live in behaving mice by 2-photon microscopy. We are also extending these studies to image microglial interactions with other glial cells and the vasculature.

A)  Prior to live imaging, a mouse with a cranial window implant is head-fixed and placed atop a foam ball under the 2-photon microscope objective.  B)  Neurons and their processes (red) were labeled by ipsilateral stereotactic injection of AAV2-hSyn-ChR2mCherry into visual cortex and microglia (green) are visualized using Cx3CR1-EGFP reporter mice. Arrow denotes one of many microglial cells in the field.  Scale bar= 50µm.

A) Prior to live imaging, a mouse with a cranial window implant is head-fixed and placed atop a foam ball under the 2-photon microscope objective. B) Neurons and their processes (red) were labeled by ipsilateral stereotactic injection of AAV2-hSyn-ChR2mCherry into visual cortex and microglia (green) are visualized using Cx3CR1-EGFP reporter mice. Arrow denotes one of many microglial cells in the field.  Scale bar= 50µm.

3.     Dissect how microglia contribute to synaptic changes in neurological disorders

It is now appreciated that abnormal synaptic connectivity is an underlying feature of neurodevelopmental and psychiatric disorders such as autism and schizophrenia. Further, early synapse loss is an underlying feature and, perhaps causative in an array of neurodegenerative diseases (Alzheimer’s disease, ALS, Parkinson’s, Multiple Sclerosis, etc.). Projects in the lab include how microglia modulate the balance of excitatory and inhibitory synaptic connectivity, which is often impaired in disorders such as autism and schizophrenia. We are also assessing how microglia modulate synaptic connectivity at early stages in neurodegeneration with a particular focus on multiple sclerosis and ALS.

 
A)  RGC inputs into the LGN were labeled by intraocular injection of anterograde tracers CTB-594 (red) and CTB-488 (green). Microglia/macrophages were labeled with anti-Iba-1 (blue).  B and C)  There was a large and significant increase in synaptic engulfment by microglia/macrophages following EAE.

A) RGC inputs into the LGN were labeled by intraocular injection of anterograde tracers CTB-594 (red) and CTB-488 (green). Microglia/macrophages were labeled with anti-Iba-1 (blue). B and C) There was a large and significant increase in synaptic engulfment by microglia/macrophages following EAE.