Strides in STXBP1 Research

What’s new in June of 2026

Scientists from Newcastle University in the UK used donated human fetal brain tissue to model STXBP1 encephalopathy and showed that lowering STXBP1 disrupts how early brain circuits form and communicate. When researchers reduced STXBP1 in developing cortical tissue, the normally synchronous activity of neurons, in a region called the subplate, became weaker and more fragmented. The subplate is region of the developing cortex where functional cortical circuits begin to form; it is important for early brain wiring. Geneexpression testing revealed broad changes in pathways involved in building synapses, guiding growing neurons, and maintaining the brain’s structural support. Several proteins tied to axon guidance and presynaptic function were altered, including a strong increase in a protein called EPHA4 (overexpression of EPHA4 has been associated with neurodegeneration). Consistent with this, neurons showed shorter neurites and abnormal buildup of EPHA4 at their growth cones. Overall, the work shows that STXBP1 loss affects not just neurotransmitter release but multiple layers of early brain development, helping explain why STXBP1 disorders lead to wideranging neurological symptoms.

Scientists from France looked at how Stxbp1 haploinsufficiency affects neurons in neonatal and juvenile mice. The study shows that young mice with only one working copy of the Stxbp1 gene go through two distinct stages of brain dysfunction. As newborns, neurons in both the hippocampus and motor cortex are overexcitable, firing more easily even though basic cell properties look normal. By the juvenile stage (1 month old), this hyperexcitability fades; however, glutamate neurons (excitatory, but not GABA neurons (inhibitory) show altered responses to fast, repeated stimulation and a lower probability of neurotransmitter release. Spontaneous background signaling remains largely normal at both ages. Biochemical tests reveal that several proteins associated with the SNARE complex (which helps neurons release neurotransmitters), are reduced only in juvenile mice. Together, the findings suggest that STXBP1 deficiency disrupts brain function in different ways at different developmental stages, first by making neurons too excitable and later by impairing how synapses sustain communication during rapid activity.

Burst suppression on an EEG is a distinctive pattern of brain activity characterized by periods of high-amplitude electrical activity alternating with periods of very low activity. Developmental and epileptic encephalopathies (DEEs) with early burst-suppression EEG (BS EEG) are among the most severe neonatal epileptic syndromes, typically presenting in the first months of life with refractory seizures and profound neurodevelopmental impairment. A team in France retrospectively analyzed 110 patients with BS EEG enrolled from a database of 1,540 individuals with suspected genetic epilepsies. Pathogenic or likely pathogenic variants were identified in 62.7% of patients and involved 23 genes. KCNQ2 (n = 24) and STXBP1 (n = 16) accounted for one-third of diagnoses, whereas SCN2A (n = 3) and KCNT1 (n = 2) were less frequent.

In KCNQ2 cases, seizures and BS onset occurred earlier than in STXBP1 cases: mean 2 days vs 6 weeks for seizures and 3 days vs 2 months for BS, respectively. In addition, the team also found that a specific pattern of BS (long bursts and shorter suppressions) were strongly correlated with KCNQ2 and STXBP1 variants. The study shows how early EEG features, particularly BS timing and morphology, can help anticipate an underlying genotype, which may help guide precision therapy.

The team at VU Amsterdam published a paper that examined a child with developmental delays who carries a rare STXBP1 splicesite variant that was originally labeled a variant of uncertain significance (VUS) because she does not have seizures, which are common in STXBP1-RD. By creating neurons from her blood cells, the team showed that this variant causes faulty RNA splicing, leading to the loss of Exon 6, a premature stop signal, and major reductions in the STXBP1 protein, similar to known diseasecausing mutations. Her neurons also showed fewer synapses and altered structure, and her EEG displayed brainactivity patterns typical of STXBP1RD, even without epilepsy. Together, these cellular and clinical findings demonstrate that the c.429+5G>A variant truly disrupts STXBP1 function and should be considered pathogenic, allowing her to be confidently diagnosed and included in the STXBP1 registry.

Chinese clinicians associated with Beijing Children’s Hospital published a retrospective clinical study of 28 children with STXBP1-RD seen at their hospital. They found that almost all had developmental delays, and half had significant intellectual disability. Most children had epilepsy—usually starting early in life—and seizure types ranged from focal seizures to generalized tonicclonic seizures and epileptic spasms. About half achieved seizure control, while others had drugresistant epilepsy. Importantly, the study reported a 10.7% rate of SUDEP. A smaller group (4 children) had developmental delays without seizures. All children carried de novo STXBP1 mutations, including missense, nonsense, splicesite, deletion, and even startcodon variants. Overall, the findings highlight how broad and variable STXBP1-RD can be. The drug 4phenylbutyrate (4PBA) is being examined in STXBP1-RD patients to see if it can help relieve symptoms such as seizures or motor problems. Researchers from the University of San Francisco examined if the drug could improve seizures or movement issues in zebrafish models of STXBP1RD. Using both automated movement tracking and brainactivity recordings, they found that 4PBA did not improve the severe movement deficit in stxbp1a mutant zebrafish and did not reduce seizurelike brain activity in stxbp1b mutants. They also used AI to identify 16 similar drugs and tested them, but none improved movement, and a few demonstrated toxicities.

The release of molecules from cells occurs via exocytosis. In humans STXBP1 is required for the release of neurotransmitters from neurons while STXBP2 and STXBP3 are primarily involved in exocytosis from non-neuronal cells. In C. elegans worms, the protein UNC-18 functions the same as STXBP1 and is necessary for neurotransmitter release. A research team from New Jersey examined a separate STXBP-like protein called UNCP18 in these worms. Their study showed that UNCP18 is found on cell membranes and is important for fertility: worms lacking it produce far fewer offspring because they often have too few sperm and sometimes have broader problems, including missing or abnormal reproductive tissue. Although UNCP18 is present in embryos, embryos without it still survive, suggesting it is not essential for early development. Overall, the work reveals that UNCP18 has key nonneuronal roles—especially in building and maintaining the germline—and positions C. elegans as a useful model for studying how STXBPrelated proteins function outside the nervous system.

Danish and German researchers studied how two proteins—DLG1 and ZDHHC5—work together to control the structure and function of primary cilia, tiny antennalike structures on many cells that help organs like the kidney sense and respond to signals. Using cell experiments and zebrafish, the researchers show that DLG1 physically interacts with ZDHHC5 and helps position other important proteins, including STXBP1, at the base of the cilium. When either protein is missing, cilia become abnormally long and kidney structures develop abnormally, leading to swelling, cystlike changes, and other features seen in ciliopathies (diseases caused by faulty cilia). The findings highlight that STXBP1 is part of a broader structural and signaling system beyond synaptic function, suggesting that STXBP1RD may involve not only brain communication problems but also deeper defects in how cells sense and respond to their environment.