Biology subjects

O'Brien, D. F.

Publications and source records attributed to O'Brien, D. F..

4 recordsLinked to original sources

bioRxiv2025

Endothelial tight junctions and cell-matrix adhesions reciprocally control blood-brain barrier integrity

Brain endothelial cells (ECs) rely on mechanical cues to provide a physical barrier that protects the brain. Yet how ECs integrate forces to establish and maintain the blood-brain barrier (BBB) remains poorly understood. Here, we show that the two main endothelial force-bearing systems, tight junctions and cell-matrix adhesions, reciprocally control BBB integrity. Using a combination of super-resolution imaging and biophysical techniques, we reveal increasing mechanical loads on cell-cell junctions vs. cell-matrix adhesions in human stem cell-derived ECs during BBB maturation. This force redistribution is enabled by cytoskeletal remodeling, a compacted pattern of the tight junction protein claudin-5, and the emergence of specialised perinuclear cell-matrix adhesions. Mechanistically, we find an inverse relationship between claudin-5 levels and the expression of key cell-matrix adhesion proteins zyxin and vinculin in vitro and in mice. Finally, we demonstrate that this mechanobiological signature associated with BBB maturation is reversed upon BBB dysfunction after seizures in mice and in human patients with temporal lobe epilepsy. Collectively, our findings establish a novel interplay between mechanoresponsive elements in brain ECs, with implications for BBB stabilisation therapy in epilepsy.

neuroscience↗

bioRxiv2023

Immunoproteasome deficiency results in accelerated brain aging and epilepsy

The immunoproteasome is a central protease complex required for optimal antigen presentation. Immunoproteasome activity is also associated with facilitating degradation of misfolded and oxidized proteins, which prevents cellular stress. While extensively studied during diseases with increasing evidence suggesting a role for the immunoproteasome during pathological conditions including neurodegenerative diseases, this enzyme complex is believed to be mainly inactive in the healthy brain. Here, we show an age-dependent increase in polyubiquitination in the brain of wild-type mice, accompanied with induction of immunoproteasomes, which was most prominent in neurons and microglia. In contrast, mice completely lacking immunoproteasomes (triple-knockout (TKO) mice deficient for LMP2, LMP7 and MECL-1), displayed a strong increase in polyubiquitinated proteins already in the young brain and developed spontaneous epileptic seizures, beginning at the age of 6 months. Injections of kainic acid led to high epilepsy-related mortality of aged TKO mice, confirming increased pathological hyperexcitability states. Notably, the expression of the immunoproteasome was reduced in the brains of patients suffering from epilepsy. In addition, aged TKO mice showed increased anxiety, tau hyperphosphorylation and degeneration of Purkinje cell population with the resulting ataxic symptoms and locomotion alterations. Collectively, our study suggests a critical role for the immunoproteasome in the maintenance of a healthy brain during aging.

neuroscience↗

bioRxiv2022

MicroRNA inhibition using antimiRs in acute human brain tissue sections

IntroductionAn emerging pre-clinical approach for the treatment of pharmacoresistant epilepsy is targeting the microRNA (miRNA) system. MiRNAs are short noncoding RNAs that suppress gene expression at the post-transcriptional level. Targeting miRNAs, which is possible using antisense oligonucleotide antimiRs can produce broad effects on gene expression suited to the complex pathophysiology in temporal lobe epilepsy. Potent anti-seizure and disease- modifying effects have been reported for antimiRs targeting microRNA-134 (antimiR-134). To date, however, pre-clinical testing has been performed using in vitro cell cultures and rodent models. It is uncertain how well this approach will translate to the clinic. Here, we develop an antimiR testing platform in human brain tissue sections. MethodologyHuman brain specimens were obtained with consent from patients undergoing resective surgery to treat focal drug-resistant epilepsy. Neocortical specimens were submerged in modified artificial cerebrospinal fluid (ACSF), dissected for clinical neuropathological examination, and unused material transferred for sectioning. Individual tissue sections were incubated in oxygenated ACSF, containing either antimiR-134 or a non-targeting control antimiR, for 24 hours at room temperature. RNA integrity was assessed using BioAnalyzer processing, and individual miRNA levels measured using RT-qPCR. ResultsACSF transport had no obvious impact on any clinical neurosurgical or neuropathological procedure and specimens were confirmed to be viable following this process. RNA was well- preserved by transportation of specimens in ACSF, with RNA integrity scores significantly higher than tissue transported without ACSF. AntimiR-134 mediated a specific and dose- dependent knockdown of miR-134 in human neocortical sections, with approximately 75% reduction of miR-134 at 1 {micro}M and 90% reduction at 3 {micro}M. These doses did not have off- target effects on expression of a selection of three other miRNAs (miR-10, miR-129 or miR- 132). SignificanceThis is the first demonstration of antimiR-134 effects in live human brain tissues. The findings lend further support to the preclinical development of miR-134 and offer a flexible platform for the pre-clinical testing of antimiRs, and other antisense oligonucleotide therapeutics, in human brain. Key pointsO_LIASO antimiRs are promising treatments for pharmacoresistant epilepsy C_LIO_LIWe developed a pipeline to preserve live human neocortical brain specimens from people undergoing resective surgery C_LIO_LIRNA integrity was sufficient to measure miRNA levels in human brain tissues transported in modified ACSF C_LIO_LIIncubation of acute human neocortical specimens in antimiR-134 resulted in potent and specific reduction in miR-134 levels C_LIO_LIAcute human brain slices are a promising model for testing ASOs C_LI

neuroscience↗

bioRxiv2019

Large-scale changes to mRNA polyadenylation in temporal lobe epilepsy

The molecular mechanisms that shape the gene expression landscape during the development and maintenance of chronic states of brain hyperexcitability are incompletely understood. Here we show that cytoplasmic mRNA polyadenylation, a posttranscriptional mechanism for regulating gene expression, undergoes widespread reorganisation in temporal lobe epilepsy. Specifically, over 25% of the hippocampal transcriptome displayed changes in their poly(A) tail in mouse models of epilepsy, particular evident in the chronic phase. The expression of cytoplasmic polyadenylation binding proteins (CPEB1-4) was found to be altered in the hippocampus in mouse models of epilepsy and temporal lobe epilepsy patients and CPEB4 target transcripts were over-represented among those showing poly(A) tail changes. Supporting an adaptive function, CPEB4-deficiency leads to an increase in seizure severity and neurodegeneration in mouse models of epilepsy. Together, these findings reveal an additional layer of gene expression control during epilepsy and point to novel targets for seizure control and disease-modification in epilepsy.

neuroscience↗