TGF-β signaling promotes astroglial activation and TDP-43 proteinopathy in organoid models of frontotemporal lobar degeneration

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Abstract

Dominant mutations in progranulin (GRN) gene cause frontotemporal lobar degeneration (FTLD-GRN), whereas homozygous GRN mutations lead to neuronal ceroid lipofuscinosis, a childhood neurodegenerative disorder. While recent transcriptomic studies reveal profound glial and neuronal pathology in FTLD-GRN at the disease end stage, the mechanism that disrupts glia-neuron homeostasis remains unclear. Using induced pluripotent stem cell–derived cortical organoids, we showed that GRN–/– and GRNR493X mutations led to precocious astrogliosis that promoted neuronal stress and synaptic loss. Single-cell transcriptomics and histopathology analyses revealed a robust activation in the TGF-β signaling pathway in GRN–/– and GRNR493X/R493X astrocytes, which was accompanied by features of immune activation, loss of synaptic support, and abundant pTDP-43+ fibrils in astroglial cytoplasm, a feature characteristic of FTLD-GRN. Intriguingly, blocking TGF-β signaling mitigated astroglial activation and pTDP-43 proteinopathy in GRN–/– organoids. Together, these results provide insights into the cell-autonomous role of astroglial activation in neurodegeneration caused by progranulin deficiency.

Authors

Arren C. Ramsey, Xiao-Yan Tang, Magdalena J. Macias, Patricia R. Nano, Rufei Lu, Brian Benito, Cameron M. Lau, Jisu Park, Jiasheng Zhang, Wandy Beatty, Tanzila Mukhtar, Arnold R. Kriegstein, Aparna Bhaduri, Elise Marsan, Eric J. Huang