Biology subjects

Neal, E.

Publications and source records attributed to Neal, E..

5 recordsLinked to original sources

bioRxiv2025

Transcription-dependent phase coexistence of mitochondrial nucleoids and RNA granules

The spatiotemporal organization of multiple components within biomolecular condensates helps coordinate gene expression. Mitochondria separate transcription and RNA processing into two distinct condensates: mt-nucleoids and mtRNA granules (MRGs), respectively. However, how mtRNA transcripts are transferred from mt-nucleoids to distant MRGs was unclear. With high-resolution imaging, we examined the steady-state organization of mt-condensates in human cells. We identified a wide distribution of distances between centroids of mt-condensates, from roughly a micron apart to within 100 nm of each other. Live imaging revealed that such organization was dynamic: mt-condensates frequently underwent cycles of mixing and demixing. Indeed, mtRNA transcripts and the mtRNA polymerase co-localized within mixed mt-condensates, while transcription inhibition led to complete dissolution of MRGs, supporting that nascently transcribed mtRNA is a key driver of mt-condensate organization. Together, our results show that active transcription sustains the phase coexistence between mt-nucleoids and MRGs, with implications for transcriptional condensates more broadly.

cell biology↗

bioRxiv2023

IQGAP2 regulates blood-brain barrier immune dynamics

Brain endothelial cells (BECs) play an important role in maintaining central nervous system (CNS) homeostasis through blood-brain barrier (BBB) functions. BECs express low baseline levels of adhesion receptors, which limits entry of leukocytes. However, the molecular mediators governing this phenotype remain mostly unclear. Here, we explored how infiltration of immune cells across the BBB is influenced by the scaffold protein IQ motif containing GTPase activating protein 2 (IQGAP2). In mice and zebrafish, we demonstrate that loss of Iqgap2 increases infiltration of peripheral leukocytes into the CNS under homeostatic and inflammatory conditions. Using single-cell RNA sequencing and immunohistology, we further show that BECs from mice lacking Iqgap2 exhibit a profound inflammatory signature, including extensive upregulation of adhesion receptors and antigen-processing machinery. Human tissue analyses also reveal that Alzheimers disease is associated with reduced hippocampal IQGAP2. Overall, our results implicate IQGAP2 as an essential regulator of BBB immune privilege and immune cell entry into the CNS.

neuroscience↗

bioRxiv2022

Reactive astrocytes transduce blood-brain barrier dysfunction through a TNFα-STAT3 signaling axis and secretion of alpha 1-antichymotrypsin

Astrocytes are critical components of the neurovascular unit that support blood-brain barrier (BBB) function in brain microvascular endothelial cells (BMECs). Transformation of astrocytes to a reactive state in response to injury and disease can be protective or harmful to BBB function, but the underlying mechanisms for these effects remain mostly unclear. Using a human induced pluripotent stem cell (iPSC)-derived coculture model of BMEC-like cells and astrocytes, we found that tumor necrosis factor alpha (TNF) transitions astrocytes to an inflammatory reactive state through activated STAT3 signaling, whereby the resultant astrocytes disrupt passive BBB function and induce vascular cell adhesion molecule 1 (VCAM-1) expression in the BMEC-like cells. These associations between inflammatory reactive astrocytes, STAT3 activation, and vascular VCAM-1 expression were corroborated in human postmortem tissue. Bioinformatic analyses coupled with CRISPR interference techniques in the iPSC model revealed that inflammatory reactive astrocytes transduce BBB disruption in part through SERPINA3, which encodes alpha 1-antichymotrypsin (1ACT), a secreted serine protease inhibitor associated with aging, neuroinflammation, and Alzheimers disease. In murine ex vivo cortical explant cultures, shRNA-mediated silencing of Serpina3n in astrocytes reduced vascular VCAM-1 expression after TNF challenge. Further, direct treatment with recombinant Serpina3n in both ex vivo explant cultures and the brain in vivo (via intracerebroventricular injection into wild-type mice) was sufficient to induce vascular VCAM-1 expression and reduce tight junction integrity. Overall, our results define the TNF-STAT3 signaling axis as a driver of an inflammatory reactive astrocyte subtype responsible for BBB dysfunction. Our results also identify 1ACT as an explicit mediator of BBB damage and suggest that inhibition of 1ACT expression or activity could represent a therapeutic avenue for reversing BBB deficits in aging and neurodegenerative disease.

neuroscience↗

bioRxiv2021

Influence of basal media composition on barrier fidelity within human pluripotent stem cell-derived blood-brain barrier models

It is increasingly recognized that brain microvascular endothelial cells (BMECs), the principle component of the blood-brain barrier (BBB), are highly sensitive to soluble cues from both the bloodstream and the brain. This concept extends in vitro, where the extracellular milieu can also influence BBB properties in cultured cells. However, the extent to which baseline culture conditions can affect BBB properties in vitro remains unclear, which has implications for model variability and reproducibility, as well as downstream assessments of molecular transport and disease phenotypes. Here, we explore this concept by examining BBB properties within human induced pluripotent stem cell (iPSC)-derived BMEC-like cells cultured under serum-free conditions in different basal media with fully defined compositions. We demonstrate notable differences in both passive and active BBB properties as a function of basal media composition. Further, RNA sequencing and phosphoproteome analyses revealed alterations to various signaling pathways in response to basal media differences. Overall, our results demonstrate that baseline culture conditions can have a profound influence on the performance of in vitro BBB models, and these effects should be considered when designing experiments that utilize such models for basic research and preclinical assays.

neuroscience↗

bioRxiv2020

Default Mode Network Ventral Hub Connectivity Associated with Memory Impairment in Temporal Lobe Epilepsy Surgery

In patients undergoing surgery for intractable temporal lobe epilepsy, the relationship between the default mode network and patients neurocognitive outcome remains unclear. The objective of this study is to employ non-invasive network mapping to identify the relationship between subdivisions of the default mode network and neurocognitive function before and after epilepsy surgery in patients with temporal lobe epilepsy. Twenty-seven medically patients with medically refractory temporal lobe epilepsy were prospectively enrolled and received resting state functional MRI and neuropsychological testing both pre- and post-operatively. Connectivity within the default mode network was modeled and average connectivity within the networks was calculated. Higher pre-operative connectivity in the ventral default mode network hub correlated with impaired baseline performance in a visual memory task. Post-operatively, a decrease in ventral but not dorsal default mode network connectivity was correlated with a deterioration of verbal and logical memory after surgery. Overall, higher connectivity in the ventral default mode network hub was associated with poor memory function in patients with temporal lobe epilepsy both before and after temporal lobe surgery. Pre-operatively, higher ventral connectivity was associated with worse visual function. Post-operatively, decreased connectivity of the ventral and dorsal default mode network was correlated with a greater decrease in logical and verbal memory when compared with the pre-operation baseline. An imbalance in default mode network connectivity towards the ventral stream and more widespread epilepsy networks may be used to predict memory impairments following surgical intervention and may lead to more tailored surgical decision making based on this non-invasive network modeling.

neuroscience↗