Summary: For years, Fragile X syndrome (FXS)—the most common inherited cause of intellectual disability—has been studied primarily through the lens of neurons. New research from the Salk Institute reveals that astrocytes, the star-shaped glial cells that support neurons, play a central role in FXS symptoms. By selectively suppressing a specific protein pathway, researchers reduced seizure severity and restored synaptic balance in a mouse model, highlighting astrocytes as promising therapeutic targets.
Researchers suppressed Bone Morphogenetic Protein (BMP) signaling specifically within astrocytes and observed a notable improvement in FXS-related deficits. The work shifts focus from neurons alone to include non-neuronal cells as critical contributors to neurodevelopmental disorders and points toward new strategies for treatment.
Key facts
- BMP signaling is elevated in FXS astrocytes: Salk researchers identified chronic upregulation of Bone Morphogenetic Protein (BMP) signaling in astrocytes from fragile X syndrome models.
- Seizure severity is reduced: Genetically suppressing BMP signaling in astrocytes produced a significant decline in audiogenic seizure severity in male FXS mice, a commonly used preclinical symptom measure.
- Synaptic function is partially restored: The astrocyte-specific intervention partially rescued inhibitory synaptic activity in the auditory cortex, a brain region often hypersensitive in FXS and autism spectrum disorder.
- Broader applicability: The methods developed to profile astrocyte proteins and RNAs in living tissue can be applied to other neurodevelopmental conditions such as Down syndrome and Rett syndrome, helping reveal shared cellular mechanisms.
Fragile X syndrome and the role of astrocytes
Fragile X syndrome arises from loss of the fragile X messenger ribonucleoprotein (FMRP), a single-gene cause that produces a wide range of cognitive, behavioral, and physical symptoms. About 40 percent of people with FXS also meet criteria for autism spectrum disorder. There is no cure; current approaches focus on symptom management through therapies and medications.
Neuronal dysfunction in FXS has been well documented—especially abnormalities in synapses and dendritic spine structure. Yet astrocytes regulate synaptic activity, shape the extracellular environment, and support neuronal development and function. Changes in astrocyte genes and proteins can therefore propagate widespread neural dysfunction, and previous studies from the Allen lab and others showed astrocyte-specific molecular alterations in FXS.
Targeting BMP signaling in astrocytes
Building on prior work that identified dysregulated genes and proteins in FXS astrocytes, the Salk team focused on the BMP pathway, which they found upregulated in FXS astrocytes. To test whether suppressing BMP signaling in astrocytes could alter disease-relevant outcomes, the researchers generated a conditional knockout (cKO) of Smad4 in astrocytes to specifically dampen BMP signaling in those cells within an intact mouse brain.
Suppressing BMP signaling in astrocytes reduced audiogenic seizure severity in male FXS mice. The authors then performed in vivo transcriptomic and proteomic profiling of cortical astrocytes to compare molecular changes across conditions. They found that FXS astrocytes show upregulation of metabolic pathways and downregulation of secretory machinery, secreted proteins, and membrane proteins. Importantly, many of these alterations were mitigated when BMP signaling was suppressed in astrocytes.
Functionally, astrocyte-specific Smad4 cKO restored deficits in inhibitory synapses within the auditory cortex, consistent with improved synaptic balance and reduced sensory hypersensitivity. The study also revealed limited overlap between RNA and protein changes in FXS astrocytes, underscoring the need to examine multiple molecular layers to understand disease mechanisms.
Implications for future research and therapeutics
These findings demonstrate that astrocytes contribute materially to some molecular and functional phenotypes of FXS, and that targeting astrocyte BMP signaling can improve measured symptoms in a mouse model. Because BMP pathway components are already studied in other areas of medicine, the pathway represents a concrete, druggable target for future therapeutic development.
The study also produced a valuable experimental toolkit and datasets for profiling astrocyte-specific RNA and protein changes in an intact brain. These resources can now be applied to other neurodevelopmental disorders—enabling investigations into whether shared astrocyte-driven mechanisms underlie overlapping symptoms across conditions.
Authors and funding
Authors include James Deng, Adrien Paumier, Lara Labarta-Bajo, Ashley Brandebura, Nick Andrews, Tao Tao, Reina Bassil, Antonio Pinto, Jolene Diedrich, Samuel Kahn, and Nicola J. Allen.
Funding: Supported by the National Institutes of Health, FRAXA Research Foundation, Chan Zuckerberg Initiative, UC San Diego, George E. Hewitt Foundation, Helmsley Charitable Trust, Waitt Foundation, and additional institutional grants and training awards.
Key questions answered
A: Although FXS originates from a single genetic mutation (loss of FMRP), that mutation triggers a cascade of molecular changes across multiple cell types. Gene correction remains a long-term goal, but targeting downstream cellular dysregulation—such as astrocyte-derived protein imbalances—can provide a nearer-term route to reduce severe symptoms like seizures and sensory overload.
A: Neurons are the primary signal carriers, but astrocytes are the support network that maintains the environment required for accurate neuronal communication. If astrocytes are dysfunctional, neuronal signaling can become noisy or imbalanced, impairing brain function even though the neurons themselves remain present.
A: This research is preclinical and was carried out in mouse models, but it identifies the BMP pathway—a well-studied signaling cascade—as a concrete target. The existing knowledge of BMP signaling in other fields could accelerate the development of small molecules or biologics aimed at modulating this pathway for clinical testing.
Editorial notes
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full by editorial staff.
- Additional context provided by the reporting team.
About this research news
Author: Salk Communications
Source: Salk Institute
Contact: Salk Communications – Salk Institute
Image credit: Neuroscience News
Original research: Open access. Title: “Suppression of astrocyte BMP signaling improves molecular signatures and functional deficits in a fragile X syndrome mouse model” by James Deng et al., published in 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 characterized by molecular, neuroanatomical, and behavioral changes. Astrocytes in FXS express dysregulated gene and protein networks, so identifying upstream pathways that drive those changes may provide points of intervention. The authors focused on the BMP pathway, which is upregulated in FXS astrocytes. Using an astrocyte-specific conditional Smad4 knockout to suppress BMP signaling, they observed reduced audiogenic seizure severity in male FXS mice. In vivo transcriptomic and proteomic profiling of cortical astrocytes revealed metabolic pathway upregulation and downregulation of secretory machinery, secreted proteins, and membrane proteins in FXS astrocytes—alterations that were mitigated when BMP signaling was suppressed. Functionally, astrocyte Smad4 cKO restored inhibitory synapse deficits in the FXS auditory cortex. These results indicate astrocytes contribute to some FXS molecular and functional phenotypes, and that targeting astrocyte BMP signaling improves certain FXS symptoms.