Summary: Two recent lines of research deepen our understanding of how cellular signaling controls nervous system health. One study in the nematode Caenorhabditis elegans highlights the oncogene Src (called SRC-1 in worms) as a key regulator of axon guidance during nervous system development, illustrating how a molecule known for its role in cancer also performs essential functions in normal growth and differentiation. A separate University of Cincinnati study, published June 21 in Nature Communications and led by Agnes (Yu) Luo, PhD, reveals that microglia in the adult brain produce the TGF-β1 ligand themselves and use it in an autocrine manner to maintain homeostasis and prevent neuroinflammation, a mechanism required to preserve cognitive function in mice.
Key Facts:
- Nervous system development: In C. elegans, SRC-1 (the Src homolog) guides axons during neuronal growth, demonstrating Src’s physiological role beyond its oncogenic activity.
- Microglial autocrine signaling: In mice, microglia are the primary source of TGF-β1 ligand in the adult brain and use this ligand to signal to themselves, maintaining a balanced, noninflammatory state.
- Consequences of ligand loss: Genetic deletion of microglial TGF-β1 leads to widespread neuroinflammation and cognitive deficits in animal models, establishing a causal link.
- Therapeutic implications: Restoring or enhancing TGF-β signaling in the brain could offer new approaches to limit neuroinflammation and preserve or recover cognitive function after injury or during aging.
Source: University of Cincinnati and related research on C. elegans
The University of Cincinnati team, with Agnes (Yu) Luo as corresponding author, examined the source and spatial regulation of TGF-β signaling in the adult central nervous system. TGF-β signaling has long been associated with microglial development and function, but where the necessary ligand comes from and how it is regulated within the adult brain had remained unclear. Using advanced genetic and single-cell approaches, the researchers demonstrate that microglia themselves produce TGF-β1 ligands and that this production is tightly controlled at the level of individual cells.
Luo and coauthors explain that signaling pathways require both a ligand and a receptor: the ligand binds the receptor to initiate downstream effects. Their data indicate that microglia—not astrocytes or neurons—are the principal producers of TGF-β1 needed to maintain microglial homeostasis in the adult brain. The team found that each microglial cell generates its own ligand, which engages receptors on the producing cell’s surface in an autocrine loop, keeping that cell in a steady, noninflammatory state.
This discovery resolves an important question about spatial regulation: rather than relying on a diffuse or distant source of TGF-β, the brain maintains precise local control through cell-autonomous ligand production. As graduate student and coauthor Elliot Wegman described it, microglia behave in a locally “selfish” way—each cell produces ligand to preserve its own balanced state—which enables precise regulation of inflammation in discrete brain microenvironments.
Using inducible and mosaic genetic knockouts in mice, the researchers showed that removing TGF-β1 production specifically from microglia triggers a dyshomeostatic microglial transcriptome resembling profiles seen in disease, injury, and aging. Astrocytes in these models also adopt a transcriptome similar to inflammation-associated astrocytes. Importantly, mice lacking microglial TGF-β1 develop widespread neuroinflammation and measurable cognitive deficits, supporting the conclusion that microglial-derived TGF-β1 is necessary to maintain normal cognitive function.
Looking ahead, Luo’s team plans to test whether boosting TGF-β ligand levels or otherwise restoring microglial TGF-β signaling can slow, stop, or reverse cognitive decline caused by compromised signaling—whether due to disease, injury, or aging. The long-term aim is to modify the brain environment to better support neuron survival and promote repair following damage, by harnessing a finely tuned, cell-autonomous signaling mechanism.
Funding: This study was funded by the National Institutes of Health (grants R01NS127074 and F31NS125930).
Additional coauthors include Alicia Bedolla, Max Weed, Kierra Ware, Anastasia Alkhimovitch, Igal Ifergan, Aleksandr Taranov, Joshua D. Peter, Lucas McClain, Messiyah K. Stevens (Vanderbilt University), Rosa Maria Salazar Gonzalez, J. Elliott Robinson, Aditi Paranjpe, Krishna M. Roskin (Cincinnati Children’s Hospital Medical Center), and Nigel H. Greig (National Institute on Aging).
About this genetics and neurodevelopment research news
Author: Tim Tedeschi
Source: University of Cincinnati
Contact: Tim Tedeschi – University of Cincinnati
Image: Image credited to Neuroscience News
Original Research: “Adult microglial TGFβ1 is required for microglia homeostasis via an autocrine mechanism to maintain cognitive function in mice” by Agnes (Yu) Luo et al., published in Nature Communications. The paper is open access.
Abstract
Adult microglial TGFβ1 is required for microglia homeostasis via an autocrine mechanism to maintain cognitive function in mice
TGF-β signaling is essential for microglial function, but the cellular source and spatial regulation of the TGF-β1 ligand in the adult central nervous system were previously unclear. The data presented in this study support that microglia—not astrocytes or neurons—are the primary producers of TGF-β1 ligands required for microglial homeostasis. Microglia-specific Tgfb1 knockout (MG-Tgfb1 KO) produces activated microglia with a dyshomeostatic transcriptome resembling disease-associated, injury-associated, and aged microglia, indicating the importance of self-produced TGF-β1 in the adult CNS. Astrocytes in MG-Tgfb1 inducible KO mice display transcriptomic changes aligned with lipopolysaccharide-associated astrocyte profiles. Sparse mosaic single-cell microglial knockout experiments establish an autocrine signaling mechanism. Finally, MG-Tgfb1 inducible KO mice exhibit cognitive deficits, supporting that precise, spatially regulated microglial TGF-β1 is required for brain homeostasis and normal cognitive function in the adult brain.