Summary: Research using C. elegans shows the oncogene Src, known as SRC-1 in nematodes, is vital for nervous system development by guiding axons. The study highlights Src’s normal role in growth and differentiation, which, when mutated, leads to cancer. This work could inform new therapies for neuron damage in spinal cord injuries and stroke. Findings also resolve previous discrepancies about SRC-1’s function.
Key Facts:
- Nervous System Development: Src (SRC-1) guides axons in neuron growth.
- Normal vs. Mutated: Understanding Src’s normal function helps explain its role in cancer.
- Therapeutic Potential: Insights could lead to new treatments for spinal cord injuries and stroke.
Source: University of Cincinnati
A new study led by University of Cincinnati researchers sheds new light on the role of a signaling pathway in the brain to maintain health and prevent inflammation and cognitive deficits.
UC’s Agnes (Yu) Luo, PhD, is corresponding author on the research, published June 21 in the journal Nature Communications, and focused on a signaling pathway called TGF-β that plays a number of roles depending on where it is located in the body.
Luo explained that signaling pathways in the body control different cell functions and require two components: a type of molecule called a ligand and a receptor that the ligand binds to and activates to start the signaling.
Prior to this study, it was known that the TGF-β signaling pathway was important in brain immune cells called microglia in maintaining their balance, but its role in maintaining cognitive function was largely unknown. Additionally, the precise source of the TGF-β ligand in the brain was also unknown.
Luo said the researchers used state-of-the-art tools and found for the first time that microglia make the TGF-β ligand in the brain to prevent neuroinflammation.
“Microglia cells are the innate immune cells of the brain, and what surprised us most is that they each make their own TGF-β ligand,” said Luo, professor and vice chair in the Department of Molecular and Cellular Biosciences in UC’s College of Medicine.
“This TGF-β ligand binds to the receptor on the microglia cell itself, and they use this signaling to stay in homeostasis. This self-produced ligand binds to receptors on the cell’s surface to keep each cell in a constantly balanced, and not in an inflamed, state.”
While it was previously known that TGF-β signaling helps keep microglia in balance, Luo said it was not known that microglia make the ligands themselves in a “spatially and precisely controlled” manner carried out by each individual cell, a mechanism called autocrine signaling.
“You can think of these microglia cells as being, in a way, ‘selfish,’ as they only make the ligand to keep themselves in balance and not inflamed,” said graduate student and study coauthor Elliot Wegman.
“This, thereby, provides a very precise mechanism to regulate local states of inflammation in the microenvironment of the brain.”
Using animal models, the team additionally found that when the TGF-β ligand is genetically deleted from microglia, it leads to global neuroinflammation in the brain.
“This suggests that the neuroinflammation in microglia is sufficient by itself without other causes to drive cognitive deficit,” Luo said. “We show the direct cause and link between these events.”
Moving forward, the team will investigate whether cognitive deficit can be slowed, stopped or potentially reversed by boosting the TGF-β ligand and signaling pathway in the brain under conditions where TGF-β signaling becomes compromised.
“We’re investigating whether restoring the TGF-β signaling pathway and revitalizing its signaling can then ameliorate disease-related or age-associated cognitive deficits,” she said.
“The long-term goal of our research is to modify the brain environment to better support the survival of the neurons or promote repair of the brain after injury or damage.”
Funding: This study was supported by National Institutes of Health grants (R01NS127074 and F31NS125930).
Additional coauthors and collaborators on the paper include UC’s Alicia Bedolla, Max Weed, Kierra Ware, Anastasia Alkhimovitch, Igal Ifergan, Aleksandr Taranov, Joshua D. Peter and Lucas McClain; Messiyah K. Stevens of Vanderbilt University; Rosa Maria Salazar Gonzalez, J. Elliott Robinson, Aditi Paranjpe and Krishna M. Roskin of Cincinnati Children’s Hospital Medical Center and Nigel H. Greig of the National Institutes of Health’s 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: The image is credited to Neuroscience News
Original Research: Open access.
“Adult microglial TGFβ1 is required for microglia homeostasis via an autocrine mechanism to maintain cognitive function in mice” by Agnes (Yu) Luo et al. Nature Communications
Abstract
Adult microglial TGFβ1 is required for microglia homeostasis via an autocrine mechanism to maintain cognitive function in mice
While TGF-β signaling is essential for microglial function, the cellular source of TGF-β1 ligand and its spatial regulation remains unclear in the adult CNS.
Our data supports that microglia but not astrocytes or neurons are the primary producers of TGF-β1 ligands needed for microglial homeostasis.
Microglia-Tgfb1 KO leads to the activation of microglia featuring a dyshomeostatic transcriptome that resembles disease-associated, injury-associated, and aged microglia, suggesting microglial self-produced TGF-β1 ligands are important in the adult CNS.
Astrocytes in MG-Tgfb1 inducible (i)KO mice show a transcriptome profile that is closely aligned with an LPS-associated astrocyte profile. Additionally, using sparse mosaic single-cell microglia KO of TGF-β1 ligand we established an autocrine mechanism for signaling.
Here we show that MG-Tgfb1 iKO mice present cognitive deficits, supporting that precise spatial regulation of TGF-β1 ligand derived from microglia is required for the maintenance of brain homeostasis and normal cognitive function in the adult brain.
