The researchers started from a deceptively simple premise. Acetylation, a post-translational modification in which acetyl groups are added to proteins, is known to govern vascular development, inflammatory responses, and cellular behavior in disorders ranging from atherosclerosis to thoracic aortic aneurysms. Yet its role in moyamoya disease had barely been explored. To fill that gap, the team mined publicly available transcriptomic datasets from the Gene Expression Omnibus, combining microarray data from 32 middle cerebral artery wall samples and eight superficial temporal artery samples, then intersected the resulting differentially expressed genes with a predefined set of 73 acetylation-regulatory genes.

That intersection yielded 19 acetylation-related differentially expressed genes, including BAZ1B, BRD3, and BRD7. Using consensus clustering, a statistical method that repeatedly reassigns samples to groups to test how stably they cohere, the researchers found that moyamoya disease splits most cleanly into two molecular subtypes when classified by the expression of these acetylation-related genes. The two clusters, labeled C1 and C2, were not merely statistical artifacts. Transcriptome-wide differential expression between them revealed 472 genes that varied by subtype, and pathway enrichment analysis showed that each cluster carried a distinct biological signature involving hypoxic injury, vascular remodeling, angiogenesis, and immune-inflammatory activity.

From this molecular heterogeneity, five candidate genes rose to the top: STK39, NEO1, PKNOX1, GOLT1B, and MTMR12. Each was expressed at lower levels in moyamoya disease than in non-moyamoya surgical controls, though the authors are careful to note that none met the transcriptome-wide false discovery rate threshold in the primary comparison. STK39 did cross that threshold when moyamoya samples were compared specifically with epilepsy controls, giving the team an exploratory but meaningful signal to pursue. STK39 encodes STE20-related proline/alanine-rich kinase, or SPAK, a downstream effector of WNK kinases that regulates cation-chloride cotransport and cellular ion homeostasis, and has previously been implicated in hypertension, Parkinson’s disease susceptibility, and autism risk.

To test whether these candidates were biologically relevant rather than statistical curiosities, the researchers measured serum concentrations of STK39 and MTMR12 by ELISA in a small preliminary cohort of three moyamoya patients and three healthy controls. Both proteins were significantly decreased in the patient group, with P values of 0.0140 and 0.0055 respectively. The authors stress that this sample size is far too small to constitute independent validation, but the concordance between transcriptomic and serum findings provided enough preliminary support to justify moving STK39 into the laboratory for functional testing.

That functional work took place in human brain microvascular endothelial cells, the very cells that line the cerebral microvasculature and bear the brunt of moyamoya pathology. Using siRNA-mediated knockdown, the researchers silenced STK39 and exposed the cells to either normal oxygen levels or hypoxic conditions mimicking the chronic cerebral hypoperfusion that defines the disease. The results were striking. Under hypoxia, STK39 knockdown promoted endothelial cell migration while simultaneously inhibiting proliferation, a combination that hints at the abnormal vascular remodeling seen in moyamoya disease, where vessels proliferate pathologically rather than functionally.

The molecular consequences of losing STK39 were equally revealing. Knockdown increased the expression of HIF-1α, the master transcriptional regulator of the hypoxic response, along with phosphorylated STAT3, cleaved Caspase-3, IL-6, CCL2, and VCAM-1. Together, these markers paint a picture of endothelial cells caught in a state of inflammatory activation and apoptotic stress, precisely the kind of endothelial dysfunction that could drive the intimal hyperplasia and vascular occlusion characteristic of moyamoya disease. The STAT3 pathway in particular is well established as a driver of angiogenesis and vascular smooth muscle cell phenotype switching, and the immune infiltration analysis showed that monocytes and macrophages differed significantly between the two molecular subtypes, linking the kinase to a broader inflammatory ecosystem.

Perhaps the most intriguing therapeutic signal came from trichostatin A, a histone deacetylase inhibitor added to the hypoxic, STK39-deficient cells as an exploratory pharmacological intervention. TSA partially reversed the enhanced migration, restored some of the lost proliferation, reduced the global lysine acetylation signal that had been elevated by the treatment, and dampened the expression of HIF-1α, phosphorylated STAT3, cleaved Caspase-3, IL-6, CCL2, and VCAM-1. While the authors emphasize that this does not establish acetylation-dependent regulation of STK39 itself, the partial rescue suggests that the acetylation machinery sits somewhere in the same pathological circuit and could represent a target for future mechanistic studies.

The study is candid about its limitations. The transcriptomic analysis relied on small, heterogeneous surgical control groups that included patients with intracranial aneurysms and epilepsy rather than perfectly matched healthy vessels. The serum validation involved only six participants. The in vitro hypoxia model represents an acute and simplified reduction in oxygen availability that cannot reproduce the chronic, fluctuating hemodynamic environment, altered shear stress, or the complex interactions among endothelial cells, smooth muscle cells, and immune cells that define moyamoya vascular pathology. The molecular clusters were defined from gene expression rather than direct measurements of protein acetylation, so they should not be read as confirmed high- and low-acetylation states.

Even with those caveats, the findings add a genuinely new dimension to moyamoya research. The disease has traditionally been framed through the lens of RNF213, the best-established susceptibility gene, and through vascular smooth muscle cell abnormalities. This study suggests that the molecular pathology extends beyond a single genetic determinant into a network of post-translational modification regulators, immune cell interactions, and hypoxia-driven endothelial responses. STK39, sitting at the intersection of ion homeostasis, blood pressure regulation, nitric oxide signaling, and now endothelial inflammatory activation, emerges as a candidate gene worth pursuing in larger, independent cohorts. If future work confirms its role and clarifies its relationship with acetylation pathways, it could open a path toward targeted interventions for a disease whose effective diagnosis and treatment remain limited precisely because its pathogenesis has stayed hidden for so long.

Subject of Research: Moyamoya disease

Article Title: STK39 is associated with endothelial dysfunction and inflammatory activation under hypoxic conditions in moyamoya disease

Article References: STK39 is associated with endothelial dysfunction and inflammatory activation under hypoxic conditions in moyamoya disease. (n.d.). https://doi.org/10.3389/fnhum.2026.1854099

Image Credits: AI Generated

DOI: 10.3389/fnhum.2026.1854099

Keywords: moyamoya disease, STK39, acetylation, endothelial dysfunction, hypoxia, inflammation, cerebrovascular disease, STAT3, HIF-1α, trichostatin A, associated, endothelial