Findings establish OCNDS as a disorder of compartment-specific translational dysregulation driven by impaired CK2α–G3BP1 control of RNA granule homeostasis, and establish G3bp1 knockdown rescues translational and morphological phenotypes across all OCNDS alleles.
Abstract
Neurodevelopmental disorders are frequently caused by mutations in pleiotropic kinases, yet downstream effectors driving neuronal pathology remain undefined. Here, we identify the G3BP1-dependent stress granule pathway as the dominant effector of casein kinase 2 (CK2α) in developing neurons, implying that its dysregulation underlies the neurodevelopmental deficits of Okur-Chung neurodevelopmental syndrome (OCNDS). OCNDS-associated CK2α mutations reduce phosphorylation of G3BP1 at serine 149, promoting aberrant phase separation and persistent granules that sequester neuronal mRNAs and suppress local protein synthesis across axonal and dendritic compartments. These phenotypes produce allele-specific deficits in neuronal morphogenesis, synaptic abundance, and network excitability, which are conserved in a knock-in mouse model and in patient-derived iPSC neurons. G3bp1 knockdown rescues translational and morphological phenotypes across all OCNDS alleles, demonstrating that restoring granule homeostasis reverses neuronal pathology. Together, these findings establish OCNDS as a disorder of compartment-specific translational dysregulation driven by impaired CK2α–G3BP1 control of RNA granule homeostasis. Summary OCNDS mutations disrupt CK2α–G3BP1 signaling, causing persistent granules and defective neuronal translation and development.
The RNA binding G3BP1 is depleted in several neurodegenerative diseases, yet its functional consequences at the cellular level remain poorly understood. While best known for its critical role in stress granule formation, we demonstrate that G3BP1 also stabilises the COPI vesicle protein beta-COP by promoting its interaction with the deubiquitinase USP10. G3BP1 depletion disrupts this interaction leading to increased ubiquitination of beta-COP, which accelerates its proteasomal degradation. This leads to compromised Golgi structure and function, and impaired lysosomal homeostasis, which causes defective autophagic flux. Consequently, the autophagic clearance of α-synuclein, a protein that can drive Parkinson's disease (PD), is significantly slowed. Importantly, we observe a concurrent reduction of both G3BP1 and beta-COP protein levels in brain sections from PD and dementia with Lewy Body (DLB) patients and from a PD mouse model. These findings reveal a novel mechanistic link between G3BP1, vesicular trafficking, and proteostasis in neurodegeneration.
Sarayu Ramakrishna, Laura Ryan, S. Son et al.· Cell Death and Differentiati...· 0 citations
This study indicates that KIF2C may regulate microtubule dynamics to control deep-layer cortical neuron number and organization and modulate neuronal projections and signaling pathways and provides a foundation for understanding the role of KIF2C in neural development.
The HECT-type E3 ubiquitin ligase HUWE1 is a critical regulator of protein homeostasis, genome stability, and neurodevelopment. Variants in HUWE1 are linked to X-linked intellectual disability (XLID), yet a significant number of HUWE1 variants are noncatalytic, leaving their disease mechanisms unresolved. Here, we identify an AMBRA1-RMC1-HUWE1 signaling axis that directs HUWE1-mediated ubiquitination to mitochondria to regulate neural development. In zebrafish, noncatalytic HUWE1 variants found in XLID patients (M375I, G660R, and H669Q) recapitulate key neurodevelopmental deficits, including impaired brain growth and motor neuron defects. Global ubiquitin profiling reveals that these variants selectively disrupt the ubiquitination of mitochondrial proteins without affecting nuclear substrates. Mechanistically, AMBRA1 acts as a mitochondrial scaffold that recruits RMC1, enabling HUWE1 localization to mitochondria through direct interaction with RMC1. Disruption of this recruitment by disease-associated HUWE1 variants prevents mitochondrial targeting and impairs mitochondrial substrate ubiquitination. Notably, Urolithin A treatment ameliorates neurodevelopmental phenotypes in HUWE1-deficient zebrafish. Together, our findings define an AMBRA1-organized mitochondrial recruitment pathway in which RMC1 links HUWE1 to mitochondria, explain noncatalytic HUWE1-associated XLID, and suggest mitochondrial quality-control enhancement as a potential therapeutic strategy.
Jiamin Yi, Qin Yang, Chun Zhou et al.· Proceedings of the National...· 0 citations
Mutations in the molecular motor protein KIF1A result in a spectrum of neurodevelopmental and neurodegenerative disorders termed KIF1A-Associated Neurological Disorder (KAND). KIF1A mutations variably disrupt synaptic vesicle trafficking, but the effects of KIF1A mutations on other trafficking pathways remain unexplored. Autophagy is a conserved pathway required for neuronal homeostasis. We investigated the role of KIF1A in autophagy using gene-edited human IPSC-derived neurons. KIF1A loss inhibited the trafficking of ATG9, a transmembrane lipid scramblase necessary for autophagosome biogenesis. This deficit significantly reduced autophagosome biogenesis and the density of axonal autophagosomes. KIF1A loss also depleted lysosomes from the axon, inhibiting autophagosome maturation. In neurons gene-edited to heterozygously express a pathogenic variant linked to a Rett-like syndrome in KAND patients, we also noted significant deficits in autophagy and lysosomal trafficking. Together, these results suggest that KIF1A-mediated transport is critical to neuronal autophagy and that deficits in autophagy may contribute to pathogenesis in KAND. GRAPHICAL ABSTRACT
Carris Borland, Jacob Popolow, E. Holzbaur· bioRxiv· 0 citations
Rett syndrome (RTT) is a severe X-linked neurodevelopmental disorder caused by loss-of-function mutations in the MECP2 gene and characterized by profound impairments in neuronal maturation and synaptic connectivity. Increasing evidence indicates that astrocyte dysfunction contributes to RTT pathogenesis through non-cell-autonomous mechanisms, although the molecular pathways underlying defective astrocyte-neuron communication are only partially understood. Astrocytes are the primary source of cholesterol in the brain and support neuronal maturation and synaptic function by supplying cholesterol through ApoE-containing lipoproteins. Although alterations in brain cholesterol metabolism have been reported in RTT, the underlying cellular mechanisms and their functional consequences remain poorly investigated. Here, we studied cholesterol homeostasis in Mecp2 knock-out (KO) astrocytes and its impact on neuron-astrocyte communication. Mecp2 KO astrocytes exhibited reduced nuclear localization of the transcriptional regulator Srebp2, together with the downregulation of genes involved in cholesterol biosynthesis and transport. These molecular alterations were associated with intracellular cholesterol and desmosterol accumulation, reduced Abca1 expression and defective ApoE lipidation, despite preserved ApoE expression and cholesterol secretion. Importantly, similar alterations were detected in acutely isolated astrocytes and in the cerebral cortex of Mecp2 deficient mice, demonstrating that impaired cholesterol homeostasis extends beyond in vitro models. Functionally, cholesterol supplementation of astrocyte-conditioned medium rescued the synaptic defects induced in wild-type neurons by Mecp2 KO astrocytes. Moreover, cholesterol treatment restored pre- and post-synaptic density, as well as axon initial segment length in Mecp2 heterozygous (HET) neurons. Together, these findings identify defective astrocyte-to- neuron cholesterol trafficking as a key mechanism contributing to neuronal dysfunction in RTT and suggest that strategies aimed at restoring cholesterol functional availability might represent a promising therapeutic avenue for RTT.
Francesca M. Postogna, Noemi Giancroce, C. Cabasino et al.· bioRxiv· 0 citations
Among the many subtypes of Charcot–Marie–Tooth (CMT) disease, several result from mutations in genes encoding aminoacyl-tRNA synthetases, enzymes required for tRNA charging during cytoplasmic and mitochondrial translation. We report that activation of the integrated stress response (ISR) pathway is a shared molecular feature of tRNA synthetase-associated and other axonal CMT subtypes. RTX-117, a CNS-penetrant small molecule currently in Phase 1 clinical trials, targets eukaryotic initiation factor 2B (eIF2B), a key modulator of protein synthesis and the ISR pathway. Using cryo-EM studies, we have characterized the binding mode of RTX-117 to the eIF2B decamer. In GarsP278KY/+ mice, which develop early onset motor defects and axonal pathology that recapitulate CMT2D symptoms from tRNA synthetase mutations, RTX-117 treatment started after disease onset reduced chronic ISR activation and produced significant functional and electrophysiological improvement. We further identify ISR targets, including secreted proteins such as GDF15 and FGF21 that may serve as translational biomarkers for treatment response to RTX-117 in CMT disease. Broader surveillance of the ISR pathway across models of neurodegeneration reveals strong activation in several diseases and a correlation with disease progression, particularly in models of Alzheimer’s disease. These findings identify chronic ISR activation as a recurrent, though not universal, pathological mechanism of neurodegenerative disease models. Overall, our study identifies candidate biomarkers for CMT disease subtypes associated with defects in translational homeostasis and supports eIF2ɑ-ATF4 axis modulation as a promising therapeutic strategy for this disease class. One Sentence Summary RTX-117, a clinical stage eIF2B activator, blunts chronic ISR activation and improves nerve and motor function in a mouse model of Charcot-Marie-Tooth Disease Type 2D.
Mary McMahon, Steve Lianoglou, Sridhar Narayan et al.· bioRxiv· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
