Summary: For years, researchers focusing on Fragile X syndrome (FXS), the most common cause of inherited intellectual disability, have primarily studied neurons. However, a new study reveals that star-shaped brain cells called astrocytes play a critical role in the disorder’s symptoms.
By suppressing a specific protein pathway called BMP signaling only within astrocytes, researchers successfully reduced seizure severity and restored synaptic balance in mouse models. This discovery marks a major shift in neurodevelopmental research, positioning non-neuronal cells as high-priority targets for future therapies.
Key Facts
- The BMP Pathway: Salk researchers found that Bone Morphogenetic Protein (BMP) signaling is chronically “turned up” (upregulated) in FXS astrocytes.
- Seizure Reduction: By genetically suppressing BMP signaling specifically in astrocytes, the team observed a significant decrease in the severity of seizures, a common and distressing symptom of FXS.
- Synaptic Rescue: The intervention partially restored healthy synaptic activity in the auditory cortex, the brain region responsible for processing sound—an area often hypersensitive in people with FXS and autism.
- Beyond FXS: The tools developed for this study can now be used to investigate astrocyte protein changes in other conditions, such as Down syndrome and Rett syndrome, potentially uncovering shared biological mechanisms.
Source: Salk Institute
Fragile X syndrome (FXS) is an inherited genetic developmental condition that strongly impacts brain development.
Despite the syndrome stemming from altered genetic code for the single protein fragile X messenger ribonucleoprotein (FMRP), its symptoms are broad and variable; people with FXS can have a range of behavioral and physical symptoms, and around 40 percent of people with FXS also have autism spectrum disorder.
There is currently no cure for FXS; treatments are limited to medications and therapies to help manage symptoms.
New research from the Salk Institute found how star-shaped brain cells called astrocytes contribute to some FXS symptoms. What’s more, they found that a protein pathway commonly upregulated in FXS astrocytes could be suppressed to lessen those symptoms—meaning less severe seizures and restored molecular balances in a mouse model of FXS.
The findings, published in Nature Communications on April 23, 2026, validate the importance of studying astrocytes in FXS research and are a promising step toward future therapeutics for FXS and other developmental conditions, like Down syndrome or Rett syndrome.
“This dataset identifies astrocyte-specific alterations to proteins that allow astrocytes to regulate neurons in a whole-brain context,” says senior author of the study Nicola Allen, PhD, professor and Roger Guilleman Chair at Salk. “It’s a great resource for fragile X syndrome researchers, but also for the scientific community beyond any single disorder or condition. Using this approach, we can study astrocyte protein changes within a whole brain context and make their inclusion easier moving forward.”
What does fragile X syndrome look like in the brain?
FXS is the most common cause of inherited intellectual disability, so understanding exactly how it manifests in the brain is crucial. It makes sense, then, that scientists have been studying the role neurons play in FXS.
One consistent finding has been dysfunctional synapses, which are the junctions between neurons where information exchange occurs. Research has shown that in FXS, there are structural differences in neurons’ dendritic spines, the site of input during synaptic information exchange.
These two dysfunctions have something in common: Both synapse activity and dendritic spine morphology are regulated by astrocytes. Astrocytes are abundant non-neuronal glial cells found throughout the brain and are crucial for the development and maintenance of healthy neurons.
How do astrocytes influence fragile X syndrome symptoms?
This link between neurons and astrocytes in FXS is no surprise to the astrocyte-savvy researchers in Allen’s lab.
“Recent research, including in our lab, has shown that astrocytes have many changed genes and proteins in fragile X syndrome,” says first author James Deng, who led this project as a graduate student researcher in Allen’s lab.
“Our study accelerates this ongoing work by studying fragile X syndrome astrocytes through multiple angles in a living system, which gives us novel insights into those changes.”
Building off their previous findings that genes and proteins are dysregulated in FXS astrocytes when isolated and grown in a dish, the Salk team zeroed in on one specific dysregulated pathway: bone morphogenetic protein (BMP) signaling. According to their previous research, BMP signaling is upregulated in FXS astrocytes. What, then, would happen if it’s suppressed?
Answering that question in a physiologically relevant way meant taking their research beyond the petri dish and performing genetic astrocyte-specific manipulations on a mouse model for FXS. And so they did—creating the first mouse model with FXS in which BMP signaling was suppressed only in astrocytes.
They found that suppressing BMP signaling reduced the severity of seizures—a symptom present in some patients with FXS that can be seen in the FXS mouse model. Then, they dug into the details, looking for specific genetic and protein differences between mice with and without functional BMP signaling in astrocytes.
Using new technologies to profile the RNA and proteins of astrocytes in living systems, the researchers found metabolic and protein secretion pathways disrupted in FXS astrocytes that were improved with the intervention.
Moreover, when the researchers suppressed BMP signaling, they observed partial rescue of synaptic activity in the auditory cortex, a brain region responsible for sound processing.
“A striking aspect of our fragile X syndrome astrocyte-specific RNA and protein datasets was the low amount of overlap between syndrome-related changes at the RNA versus protein levels,” adds Allen. “It really illustrates the idea that you have to look at things from multiple different angles and levels to make impactful breakthroughs.”
What is next for fragile X syndrome research?
Multiple molecular imbalances seen in FXS astrocytes were traced to BMP signaling, and blocking that signaling led to less severe seizures and a restoration of multiple molecular pathways as well as synaptic activity.
“Seeing that targeting the BMP pathway in astrocytes alleviated some FXS symptoms makes us optimistic about astrocytes being important for consideration in future therapeutics,” says Deng.
“While there are exciting new developments in the Fragile X drug pipeline, there have historically also been a lot of struggles and failed clinical trials in this area, so we really hope our work can help accelerate patient impact.”
In addition to the specific findings around BMP signaling, the authors emphasize their excitement around this new tool for studying astrocyte-specific protein changes in many neurodevelopmental disorders.
“This opens a whole new world for similar studies in different disorders,” says Allen. “Now that James has developed the tools, we can use them in Rett syndrome or Down syndrome or other conditions.”
Other authors and funding
Other authors include Adrien Paumier, Lara Labarta-Bajo, Ashley Brandebura, Nick Andrews, and Tao Tao of Salk; Reina Bassil of Salk and UC San Diego; Antonio Pinto and Jolene Diedrich of Salk and Scripps Research Institute; and Samuel Kahn of UC San Diego.
Funding: The work was supported by the National Institutes of Health (R21 NS137659, F30 HD106699, T32GM154642, NIA 1K99AG081536-01, P30 CA01495, P30 AG068635, R24NS092943, S10-OD023689, S10-OD026929), FRAXA Research Foundation, Chan Zuckerberg Initiative, UC San Diego (URS Eureka! Research Scholarship), George E. Hewitt Foundation, Helmsley Charitable Trust, and Waitt Foundation.
Key Questions Answered:
A: While the root is a single genetic mutation (FMRP), that mutation causes a “domino effect” of protein imbalances across different cell types. Fixing the genes is the ultimate goal, but managing the “cellular noise” created by astrocytes offers a more immediate way to lessen severe symptoms like seizures and sensory overload.
A: Think of neurons as the actors and astrocytes as the stage crew. If the stage crew (astrocytes) provides the wrong lighting or moves the props incorrectly, the performance (brain function) fails. Astrocytes control the environment where neurons communicate; if they are dysfunctional, the neurons can’t send clear signals.
A: The study is in the preclinical stage (mouse models), but it identifies a very specific “druggable” target: the BMP pathway. Because this pathway is already well-studied in other areas of medicine, it provides a shortcut for researchers to develop small molecules that could eventually be tested in human clinical trials.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this neurodevelopment research news
Author: Salk Communications
Source: Salk Institute
Contact: Salk Communications – Salk Institute
Image: The image is credited to 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 with molecular, neuroanatomical, and behavioral changes.
In FXS, astrocytes express dysregulated gene and protein networks, therefore identifying upstream pathways mediating astrocyte changes may provide a point of intervention. We focus on the bone morphogenetic protein (BMP) pathway, which is upregulated in FXS astrocytes.
We generated a conditional KO (cKO) of Smad4 in astrocytes to suppress BMP signaling, finding that this lessens audiogenic seizure severity in male FXS mice.
We performed in vivo transcriptomic and proteomic profiling of cortical astrocytes, finding upregulation of metabolic pathways, and downregulation of secretory machinery and secreted and membrane proteins in FXS astrocytes, with these alterations mitigated when BMP signaling is suppressed.
Functionally, astrocyte Smad4 cKO restores deficits in inhibitory synapses in the FXS auditory cortex.
Our findings show that astrocytes contribute to some FXS mouse molecular and functional phenotypes, and targeting astrocyte BMP signaling improves some FXS symptoms.
