Developmental disorders including Autism Spectrum Disorders and Intellectual Disability can lead to reduced cortical activity. Paradoxically, these same disorders also greatly increase the risk for developing seizures. Multiple homeostatic plasticity mechanisms can compensate for reduced activity by increasing excitatory synaptic transmission and cellular excitability, and/or by decreasing inhibitory synaptic transmission. But these normally beneficial mechanisms can have maladaptive effects, especially when reduced activity is prolonged and occurs early, during a critical period of circuit formation. For example, activity blockade in vivo in rat or mouse neocortex, induces seizures, but only if it occurs early and for a prolonged period. Here we explore the mechanisms underlying this Maladaptive Compensatory Plasticity (MCP) in cultured neocortical slices. Activity blockade produces a qualitative change in subsequent synchronized activity that persists following prolonged deprivation when activity is restored. This is accompanied by a dramatic shift in the balance between excitation and inhibition. Physiological and imaging studies are consistent with a dramatic change in synaptic connectivity.
Aim 1 will identify the critical physiological features of MCP, that separate it from normal homeostatic plasticity. By blocking activity in single neurons, and by varying the timing and duration of activity blockade, we will distinguish cell autonomous from network effects, and determine which are critical for persistent effects of MCP. Using synapse imaging techniques and paired recording, we ask whether induction of MCP alters the number of functional excitatory and inhibitory synapses.
Aims 2 develops the novel idea of push/pull transcriptional regulation of homeostatic plasticity. We identify a pair of closely related transcription factors (TFs) that are potently and progressively upregulated during blockade of activity. Intriguingly, these TFs are part of a pathway that opposes compensatory plasticity, since compensatory responses are exaggerated when they are knocked out. CRISPR-based manipulations will be used to alter TF expression selectively in specific cell types. RNAseq will be used to identify candidate targets, and chromatin assays will distinguish direct and indirect targets. Finally, we will initiate in vivo studies to more directly test the role of homeostatic plasticity and its transcriptional regulation in audiogenic seizures. Together these studies may identify new strategies for mitigating maladaptive consequences of normally beneficial plasticity mechanisms.

Public Health Relevance

Developmental disorders are frequently associated with reduced brain activity and, paradoxically, with increased risk of epilepsy. This may, in part, be caused by overactive plasticity mechanisms that normally maintain appropriate levels of brain activity. Understanding negative consequences of overactive plasticity mechanisms may help prevent or treat this problem.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS109916-01A1
Application #
9896970
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Churn, Severn Borden
Project Start
2020-01-01
Project End
2023-12-31
Budget Start
2020-01-01
Budget End
2020-12-31
Support Year
1
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Brandeis University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
616845814
City
Waltham
State
MA
Country
United States
Zip Code
02453