Reprogramming of neuronal genome function and phenotype by astrocytes.

Area of Science:

• Neuroscience
• Epigenetics
• Cellular Biology

Background:

• Heterotypic cell-cell interactions, such as between neurons and astrocytes, are crucial for brain development and function.
• The mechanisms by which extracellular signals from astrocytes are translated into epigenomic regulation within neurons remain poorly understood.

Purpose of the Study:

• To investigate how astrocyte-neuron co-culture reprograms neuronal gene expression and chromatin accessibility.
• To identify functional gene regulatory elements (REs) and transcription factors (TFs) mediating astrocyte-induced neuronal changes.
• To understand the role of these interactions in neurodevelopment and neurological diseases.

Main Methods:

• Co-culture of human induced pluripotent stem cell (hiPSC)-derived neurons with mouse cortical astrocytes over several weeks.
• Analysis of gene expression and chromatin accessibility landscapes in neurons.
• Single-cell CRISPR interference (CRISPRi) and activation (CRISPRa) screens to identify functional REs and TFs.

Main Results:

• Weeks of co-culture extensively reprogramed neuronal gene expression and chromatin accessibility, affecting thousands of genes and REs, including many TFs.
• Astrocyte-responsive genes are enriched for functions in neuronal differentiation and maturation and are implicated in schizophrenia and Alzheimer's disease.
• CRISPR screens identified functional REs for approximately 50 astrocyte-responsive TF genes and demonstrated that specific TFs (e.g., POU3F2, TFAP2E) can alter neuronal morphology and electrophysiology.

Conclusions:

• Neuron-astrocyte interactions epigenetically regulate neurodevelopment and disease-relevant gene modules.
• This study provides a map of gene regulatory networks controlled by astrocytes and identifies key TFs involved.
• The findings offer a framework for understanding how the cellular microenvironment influences epigenomic programming in the brain.