The telomeric valine–arginine dipeptide repeat protein changes state to diffuse staining in mitosis and represses in vitro translation

Proceedings of the National Academy of Sciences · 2025-11-21

Translation of mammalian G-rich telomeric RNA via the Repeat Associated non-AUG (AUG, the mRNA start codon) mechanism can produce proteins consisting of long repeats of valine-arginine (VR) or glycine-leucine (GL) dipeptides. Their role in the cell has not been elucidated. Using confocal laser scanning microscopy combined with antibody staining we previously observed VR sequestered in punctate bodies and liquid droplets in the cytoplasm and nuclei of nonmitotic cells. Here, we report that cells in mitosis show diffuse VR staining throughout the cell, giving these cells a bright appearance. Upon mitotic enrichment using the cyclin-dependent kinase 1 (CDK1) inhibitor RO-3306. RO-3306, 100% of the mitotic cells showed the same diffuse staining. Antibody staining showed colocalization of VR and the L4 ribosomal protein in mitotic cells and in an in vitro firefly luciferase assay, VR depressed translation. Affinity purification combined with mass spectrometry identified ribosomal proteins as the major class of VR interacting proteins in U2OS cells including L4 along with tubulin and proteins related to neural degenerative diseases. This change from a sequestered, punctate state in interphase to dispersed diffuse staining in mitosis, and the affinity of VR for the L4 protein which lines the ribosomal exit tunnel suggests that an oligomerization change of VR may facilitate its involvement in inhibiting of global translation during mitosis. Extension to mouse embryonic cerebral cortical development showed clear staining in the ventricular zone where neural progenitor cells with a high mitotic index proliferate and in the cortical plate where new neurons settle.

Radial glia integrin avb8 regulates cell autonomous microglial TGFβ1 signaling that is necessary for microglial identity

Nature Communications · 2025-03-22 · 16 citations

Microglial diversity arises from the interplay between inherent genetic programs and external environmental signals. However, the mechanisms by which these processes develop and interact within the growing brain are not yet fully understood. Here, we show that radial glia-expressed integrin beta 8 (ITGB8) activates microglia-expressed TGFβ1 to drive microglial development. Domain-restricted deletion of Itgb8 in these progenitors results in regionally restricted and developmentally arrested microglia that persist into adulthood. In the absence of autocrine TGFβ1 signaling, microglia adopt a similar phenotype, leading to neuromotor symptoms almost identical to Itgb8 mutant mice. In contrast, microglia lacking the canonical TGFβ signal transducers Smad2 and Smad3 have a less polarized dysmature phenotype and correspondingly less severe neuromotor dysfunction. Our study describes the spatio-temporal regulation of TGFβ activation and signaling in the brain necessary to promote microglial development, and provides evidence for the adoption of microglial developmental signaling pathways in brain injury or disease.

Targeting glucose-inhibited hippocampal CCK interneurons prevents cognitive impairment in diet-induced obesity

Neuron · 2025-09-11 · 3 citations

143 Elucidating the Function of the Wnt Signaling Pathway in Hydrocephalus

Neurosurgery · 2023-03-16

INTRODUCTION: Although acquired hydrocephalus is commonly encountered by neurosurgeons, our understanding of the mechanisms underlying its pathogenesis remain poor. Furthermore, normal CSF physiology is dependent on the proper function of ventricular ependymal cells and choroid plexus epithelium (CPE), although few neurosurgical studies have addressed the functions of these cells. METHODS: Alteration of the Wnt pathway is achieved by generating FoxJ1-Cre;Apclox/lox and FoxJ1-Cre;Ctnnb1lox/lox mice, which express Cre upon induction with tamoxifen, as well as via intraventricular delivery of an AAV1-eGFP-Cre in Apclox/lox and Ctnnb1lox/lox mice. T2 weighted MRI with 3D volumetrics is applied to assess ventricular anatomy, in addition to standard molecular biology techniques to examine downstream signaling mechanisms. Kaolin and whole blood injection are used as models of obstructive and communicating hydrocephalus, respectively. RESULTS: B-catenin is strongly expressed in adult mouse ependyma and CPE, suggesting that the canonical Wnt pathway continues to be active after these cells have developed. Moreover, up-regulation of this pathway in adult FoxJ1-Cre;Apclox/lox mice results in significant ventricular enlargement (n = 3; p = 0.03). Both FoxJ1-Cre transgenic mice and intraventricular AAV1-eGFP-Cre drive selective expression within ependyma and CPE, suggesting that these may be useful models for investigating important molecular pathways within these cells. CONCLUSIONS: Our data suggests that the canonical Wnt signaling pathway plays a role in the maintenance of normal adult CSF dynamics. Moreover, we show selective targeting of ependyma and CPE using an adeno-associated virus, which may represent a novel strategy for modifying genes and/or proteins involved in CSF regulation.

Radial glia promote microglial development through integrin α _V β ₈ -TGFβ1 signaling

bioRxiv (Cold Spring Harbor Laboratory) · 2023-07-13 · 6 citations

Summary Microglia diversity emerges from interactions between intrinsic genetic programs and environment-derived signals, but how these processes unfold and interact in the developing brain remains unclear. Here, we show that radial glia-expressed integrin beta 8 (ITGB8) expressed in radial glia progenitors activates microglia-expressed TGFβ1, permitting microglial development. Domain-restricted deletion of Itgb8 in these progenitors establishes complementary regions with developmentally arrested “dysmature” microglia that persist into adulthood. In the absence of autocrine TGFβ1 signaling, we find that microglia adopt a similar dysmature phenotype, leading to neuromotor symptoms almost identical to Itgb8 mutant mice. In contrast, microglia lacking the TGFβ signal transducers Smad2 and Smad3 have a less polarized dysmature phenotype and correspondingly less severe neuromotor dysfunction. Finally, we show that non-canonical (Smad-independent) signaling partially suppresses disease and development associated gene expression, providing compelling evidence for the adoption of microglial developmental signaling pathways in the context of injury or disease.

Mapping of neuronal and glial primary cilia contactome and connectome in the human cerebral cortex

Neuron · 2023 · 85 citations

• Neuroscience
• Biology
• Cell biology

Genetic Variation Altering Cortical Progenitor Function Leads to Human Brain Evolution and Interindividual Differences in Human Brain Structure

2023-08-08

The radial unit hypothesis describes how radial glia in fetal development influence cortical size and structure in adulthood. This hypothesis serves as a framework to interpret the molecular and cellular mechanisms of human genetic variation associated with cortical structure as well as fixed differences between modern humans and archaic humans or related species contributing to modern human brain structure. Cortical-structure associated rare variants have been shown to change cellular composition by altering radial glial fate decisions and disrupt cortical architecture through aberrant radial glia scaffolds, as measured in mice and human pluripotent stem cell systems. Cortical-structure associated common variants have recently been identified by genome-wide association studies and are enriched in regulatory elements of radial glial cells. Some loci associated with cortical surface area have been linked to genes regulating cell cycle control and fate decisions via molecular quantitative trait loci. Though the study of fixed genetic variants involved in human brain evolution is still at early stages, several examples have been identified whereby these variants alter the function of radial glia to presumably increase modern human cortical size. Future research in gene regulation of radial glia will accelerate the understanding of the molecular mechanisms of brain structure associated variants.

Coordinating cerebral cortical construction and connectivity: Unifying influence of radial progenitors

Neuron · 2022-02-24 · 43 citations

Navigating the ventricles: Novel insights into the pathogenesis of hydrocephalus

EBioMedicine · 2022-03-17 · 34 citations

Congenital hydrocephalus occurs in one in 500-1000 babies born in the United States and acquired hydrocephalus may occur as the consequence of stroke, intraventricular and subarachnoid hemorrhage, traumatic brain injuries, brain tumors, craniectomy or may be idiopathic, as in the case of normal pressure hydrocephalus. Irrespective of its prevalence and significant impact on quality of life, neurosurgeons still rely on invasive cerebrospinal fluid shunt systems for the treatment of hydrocephalus that are exceptionally prone to failure and/or infection. Further understanding of this process at a molecular level, therefore, may have profound implications for improving treatment and quality of life for millions of individuals worldwide. The purpose of this article is to review the current research landscape on hydrocephalus with a focus on recent advances in our understanding of cerebrospinal fluid pathways from an evolutionary, genetics and molecular perspective.

MicroRNA-29 is an essential regulator of brain maturation through regulation of CH methylation

Cell Reports · 2021 · 73 citations

• Biology
• Neuroscience
• Cell biology

Although embryonic brain development and neurodegeneration have received considerable attention, the events that govern postnatal brain maturation are less understood. Here, we identify the miR-29 family to be strikingly induced during the late stages of brain maturation. Brain maturation is associated with a transient, postnatal period of de novo non-CG (CH) DNA methylation mediated by DNMT3A. We examine whether an important function of miR-29 during brain maturation is to restrict the period of CH methylation via its targeting of Dnmt3a. Deletion of miR-29 in the brain, or knockin mutations preventing miR-29 to specifically target Dnmt3a, result in increased DNMT3A expression, higher CH methylation, and repression of genes associated with neuronal activity and neuropsychiatric disorders. These mouse models also develop neurological deficits and premature lethality. Our results identify an essential role for miR-29 in restricting CH methylation in the brain and illustrate the importance of CH methylation regulation for normal brain maturation.