Summary: For years, Fragile X syndrome (FXS)—the most common inherited cause of intellectual disability—has been studied mainly from a neuronal perspective. New research from the Salk Institute highlights a crucial role for astrocytes, the star-shaped glial cells that support neurons. The study shows that selectively suppressing a protein pathway called BMP signaling in astrocytes reduces seizure severity and helps restore synaptic balance in an FXS mouse model, shifting attention toward non-neuronal cells as promising therapeutic targets.
Researchers genetically suppressed the Bone Morphogenetic Protein (BMP) signaling pathway exclusively in astrocytes and observed meaningful improvements in molecular and functional measures linked to FXS. These results suggest astrocytes contribute directly to some FXS symptoms and point to new directions for treatment development across related neurodevelopmental disorders.
Key Facts
- The BMP pathway: Salk scientists found that BMP signaling is chronically elevated in astrocytes from FXS models.
- Seizure reduction: Astrocyte-specific suppression of BMP signaling significantly reduced the severity of audiogenic seizures in the FXS mouse model.
- Synaptic rescue: The intervention partially restored inhibitory synaptic activity in the auditory cortex, a region that processes sound and is often hyperresponsive in FXS and autism.
- Broader relevance: The experimental tools and datasets developed in this study can be applied to examine astrocyte protein changes in other conditions, including Down syndrome and Rett syndrome, to uncover shared mechanisms.
Source: Salk Institute
About Fragile X syndrome: Fragile X syndrome is a genetic neurodevelopmental disorder that profoundly affects brain development. It arises from loss or dysfunction of the fragile X messenger ribonucleoprotein (FMRP), yet produces a wide spectrum of behavioral and physical symptoms. Approximately 40 percent of individuals with FXS also meet diagnostic criteria for autism spectrum disorder. Currently there is no cure, and care focuses on symptom management with medications and therapies.
The Salk team examined how astrocytes contribute to FXS by focusing on molecular pathways altered in these cells. Prior work from the lab showed that both gene expression and protein levels are dysregulated in FXS astrocytes when studied in isolation. In this study, investigators moved into a living system to determine whether reversing a particular dysregulated pathway would improve outcomes in a physiologically relevant setting.
The researchers concentrated on the BMP signaling pathway, which prior data indicated is upregulated in astrocytes from FXS models. They created a conditional knockout that suppresses Smad4, a core component of BMP signaling, only in astrocytes of FXS mice. This is the first mouse model in which BMP signaling is selectively dampened in astrocytes within an FXS background.
Suppressing BMP signaling produced measurable benefits: reduced severity of audiogenic seizures and partial restoration of synaptic balance in the auditory cortex. In parallel, the team applied in vivo transcriptomic and proteomic profiling to cortical astrocytes, revealing that FXS astrocytes show upregulated metabolic pathways and downregulated secretory machinery, membrane proteins, and secreted factors. Many of these molecular disturbances were lessened when BMP signaling was suppressed.
The multi-omic approach also highlighted an important point: changes observed at the RNA level do not always match changes at the protein level. This separation underscores the need to study multiple molecular layers to understand disease mechanisms and to identify effective interventions.
Why astrocytes matter: Astrocytes do not generate thoughts, but they shape the environment in which neurons communicate. They influence synapse formation, neurotransmitter clearance, metabolic support, and the composition of secreted factors that modulate neuronal activity. When astrocytes are dysfunctional, neuronal circuits can become imbalanced—contributing to symptoms such as seizures and sensory hypersensitivity seen in FXS.
Implications and next steps: The study identifies astrocyte BMP signaling as a tractable target for therapeutic development. Because BMP pathways are already well-characterized in other areas of biology, they may provide a relatively direct route toward small-molecule or biologic strategies that modulate astrocyte behavior. These findings are preclinical, limited to mouse models, but they provide a compelling rationale to broaden FXS research beyond neurons and to test whether similar astrocyte-centered approaches benefit other neurodevelopmental disorders.
The authors emphasize that the new experimental tools and datasets are a resource for the field. They plan to apply these methods to study astrocyte changes in conditions such as Down syndrome and Rett syndrome to search for common pathways that could be therapeutically targeted.
Authors and funding
Contributors to the work include James Deng, Nicola J. Allen, Adrien Paumier, Lara Labarta-Bajo, Ashley N. Brandebura, Nick A. Andrews, Reina Bassil, Tao Tao, Antonio F. M. Pinto, Jolene K. Diedrich, Samuel B. Kahn, and others affiliated with the Salk Institute, UC San Diego, and Scripps Research. Funding sources included the U.S. National Institutes of Health, FRAXA Research Foundation, Chan Zuckerberg Initiative, George E. Hewitt Foundation, Helmsley Charitable Trust, Waitt Foundation, and institutional support listed in the original publication.
Key Questions Answered:
A: Although FXS stems from a single gene mutation that disrupts FMRP, that primary defect triggers a cascade of downstream changes across many cell types. Gene repair remains an ultimate goal, but addressing the cellular disturbances—such as abnormal astrocyte signaling—can offer more immediate ways to reduce severe symptoms like seizures and sensory overload.
A: Neurons are the brain’s information carriers, but astrocytes create and maintain the environment where neurons operate. Dysfunctional astrocytes can disrupt neurotransmission, ion balance, and synaptic support, undermining neuronal function and leading to clinical symptoms.
A: This work is preclinical and performed in mouse models, but it identifies a well-defined, druggable target in the BMP pathway. Because BMP signaling has been studied in other contexts, existing knowledge could accelerate the search for candidate compounds that modulate astrocyte BMP activity for future testing.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full by staff editors.
- Additional context was added by the editorial team to clarify implications for the research community.
About this neurodevelopment research news
Author: Salk Communications
Source: Salk Institute
Contact: Salk Communications – Salk Institute
Image credit: Neuroscience News
Original Research: Open access. “Suppression of astrocyte BMP signaling improves molecular signatures and functional deficits in a fragile X syndrome mouse model” by James Deng, Adrien Paumier, Lara Labarta-Bajo, Ashley N. Brandebura, Nick A. Andrews, Samuel B. Kahn, Reina Bassil, Tao Tao, Antonio F. M. Pinto, Jolene K. Diedrich & Nicola J. Allen. Nature Communications. DOI: 10.1038/s41467-026-71919-6
Abstract
Suppression of astrocyte BMP signaling improves molecular signatures and functional deficits in a fragile X syndrome mouse model
Fragile X syndrome (FXS) is a monogenic neurodevelopmental disorder associated with molecular, neuroanatomical, and behavioral changes. Astrocytes in FXS express dysregulated gene and protein networks; identifying upstream pathways that drive these astrocyte changes offers potential points of intervention. The BMP pathway is upregulated in FXS astrocytes.
The authors generated a conditional knockout of Smad4 in astrocytes to suppress BMP signaling and found that this manipulation reduced audiogenic seizure severity in male FXS mice. In vivo transcriptomic and proteomic profiling of cortical astrocytes revealed increased metabolic pathways and decreased secretory machinery and membrane and secreted proteins in FXS astrocytes, alterations that were mitigated when BMP signaling was suppressed. Functionally, astrocyte-specific Smad4 knockout restored deficits in inhibitory synapses in the FXS auditory cortex. These results demonstrate that astrocytes contribute to some molecular and functional phenotypes in FXS, and that targeting astrocyte BMP signaling improves selected symptoms in the mouse model.