IntroductionHuntington’s disease (HD) is a devastating, autosomal-dominant neurodegenerative disorder characterized by a progressive triad of motor dysfunction, cognitive decline, and psychiatric disturbances. HD arises from an abnormal expansion of the CAG trinucleotide repeat in the Huntingtin (HTT) gene, which encodes a mutant HTT (mHTT) protein containing an expanded polyglutamine (polyQ) tract. This expanded polyQ domain confers toxic gain-of-function properties that promote aberrant protein folding and aggregation, leading to the formation of intracellular inclusion bodies and proteolytic fragments that disrupt numerous essential cellular processes. Among the best-characterized mechanisms is the ability of mHTT to abnormally bind transcription factors and chromatin-modifying enzymes, thereby inducing widespread transcriptional dysregulation and profound epigenetic reprogramming in vulnerable neuronal populations.1,2,3,4 Although neurons, particularly striatal medium spiny neurons (MSNs) are most susceptible, mHTT aggregates are also present in all major glial cell types, including astrocytes, microglia, and oligodendrocytes.5 The functional consequences of glial mHTT accumulation have gained increasing attention, as growing evidence indicates that glial pathology is not merely a secondary response but an active contributor to neurodegeneration. For example, astrocyte-specific expression of mHTT has been shown to impair glutamate uptake, calcium buffering, and synaptic support, leading to MSN vulnerability and behavioral deficits in HD mouse models.6 These findings highlight the importance of understanding astrocytic pathogenic mechanisms and raise the possibility that glial reprogramming could slow disease progression.Dysregulation of the wingless-type MMTV integration site family (WNT) signaling pathway has emerged as a prominent feature of multiple neurodegenerative conditions, including Parkinson’s disease (PD) and HD, where synaptic dysfunction represents an early hallmark of pathology.7,8,9 The WNT pathway encompasses canonical (β-catenin–dependent) and noncanonical branches, each of which regulates distinct aspects of neural development and adult brain homeostasis. Canonical WNT–β-catenin signaling governs stem cell proliferation, neurogenesis, and transcriptional regulation, while the noncanonical WNT–Ca²⁺ and WNT–planar cell polarity (PCP) pathways control cytoskeletal organization, cell polarity, migration, and calcium dynamics. Activation of the noncanonical WNT/Ca²⁺ arm stimulates the calcium-responsive nuclear factor of activated T cells (NFAT) transcription factors, enabling finely tuned regulation of gene expression programs.10,11 mHTT perturbs this system by interfering with β-catenin turnover through direct interactions with components of the β-catenin destruction complex, thereby promoting excessive stabilization of β-catenin and altering downstream transcription.12 Given that both canonical and noncanonical WNT pathways influence neuronal–glial communication, synaptic remodeling, and inflammatory responses, delineating how mHTT alters WNT signaling in specific cell types is essential for understanding the full spectrum of HD pathogenesis.Pharmacological modulation of WNT signaling has garnered considerable interest as a potential therapeutic avenue for neurodegenerative diseases. Multiple WNT-targeting compounds are under development for Alzheimer’s disease (AD), PD, and amyotrophic lateral sclerosis (ALS), reflecting the pathway’s central role in neuronal survival, inflammation, and synaptic integrity.13 However, to date, very few WNT modulators have been investigated in HD models; one exception is indomethacin, a nonsteroidal anti-inflammatory drug capable of reducing cellular β-catenin levels and attenuating polyQ-HTT–induced neuronal toxicity in primary striatal cultures expressing either wild-type HTT (480-17Q) or mutant HTT (480-68Q).14 Emerging evidence suggests that dysregulated WNT signaling in astrocytes may be particularly consequential, contributing to both reactive and dysfunctional states that compromise synaptic homeostasis, metabolic support, and neuroimmune regulation.15,16 Moreover, the interplay between WNT signaling and extracellular matrix (ECM) remodeling has recently been recognized as a critical determinant of neural circuit stability and disease progression.17 Within this framework, identifying astrocyte-specific WNT mechanisms that regulate ECM dynamics could reveal molecular targets capable of modifying disease trajectory. Genistein, a naturally occurring isoflavone derived from soybeans, has gained attention for its anti-inflammatory, antitumor, and antiangiogenic properties, coupled with an excellent safety profile even at high doses.18,19 Its pleiotropic biological activities have prompted exploration of its therapeutic potential in several neurodegenerative disorders.20 Nevertheless, the specific molecular pathways through which genistein acts in the central nervous system—particularly in relation to WNT signaling and glial pathology in HD—remain largely unexplored.In this study, we investigated the role of astrocytic WNT signaling in the pathogenesis of HD and sought to determine whether genistein modulates WNT activity to exert neuroprotective effects. Our analyses reveal that WNT5B expression is robustly elevated in astrocytes derived from both HD patients and HD mouse models. Mechanistic studies further show that WNT5B activates the noncanonical WNT signaling cascade in an NFATc2-dependent manner in striatal astrocytes, both in vitro and in vivo. Activation of astrocytic WNT5B triggers ECM degradation through the NFATc2–MMP14 axis, contributing to neuropathological alterations characteristic of HD. Finally, we demonstrate that genistein modulates this pathway by attenuating NFATc2-driven induction of MMP14, thereby reducing ECM breakdown and ameliorating neuropathological and behavioral deficits in HD mice. Collectively, these findings identify astrocytic WNT5B–NFATc2–MMP14 signaling as a critical pathological mechanism in HD and establish genistein as a promising modulator of astrocytic dysfunction with therapeutic potential.ResultsWNT5B is upregulated in the striatal astrocytes of HD postmortem brains and HD mouse modelsTo investigate how WNT signaling contributes to HD pathologies, we performed RNA sequencing (RNA-seq) on the prefrontal cortex of 20 HD patients and 49 neuropathologically normal controls.21 Among the 19 WNT genes examined, WNT5B presented the highest basal expression and was markedly upregulated in HD patients (Fig. 1a, b and Supplementary Fig. 1a). While WNT6 was also increased in the transcriptomic dataset, its relatively low basal expression level compared with that of WNT5B in both the human brain and human astrocytes (Supplementary Fig. 1b) indicates that WNT5B is the more functionally relevant isoform in the context of HD pathogenesis. Interestingly, the increase in WNT5B expression was not significantly correlated with CAG repeat length, disease duration, or disease grade in the HD patient cohort (Supplementary Fig. 1c). Western blot analysis revealed elevated WNT5B protein levels in striatal tissues from HD patients (Fig. 1c, d). Consistently, RNA-seq analysis of striatal tissue from R6/2 transgenic mice confirmed the upregulation of WNT5B (Fig. 1h, i). Immunofluorescence staining revealed that WNT5B expression was enriched in GFAP-positive astrocytes within both the caudate and putamen of HD patients (Fig. 1e–g), and colocalization analysis provided direct visual evidence of this overlap (Supplementary Fig. 1d). Similarly, increased WNT5B immunoreactivity was observed in S100β-positive astrocytes from N171-82Q mice (Fig. 1j, k). Finally, Western blot analysis revealed that, compared with wtHTT (25Q), transduction of mHTT (103Q) into human astrocytes significantly increased WNT5B protein levels (Fig. 1l–n). Collectively, these results indicate that mHTT induces WNT5B upregulation in astrocytes, which may contribute to the pathological mechanisms underlying HD.Fig. 1WNT5B is upregulated in the striatal astrocytes of HD patients and HD model mice. (a) Heatmap showing the expression levels of WNT signaling-related genes in normal subjects (Normal) and HD patients (HD). Data were extracted from GSE64810.21(b) Expression levels of WNT5B in the prefrontal cortex of 20 HD patients and 49 neuropathologically normal subjects. The error bars represent the means ± SEMs. Student’s t test was used (**, p