Biology subjects

Whitfield, T. W.

Publications and source records attributed to Whitfield, T. W..

7 recordsLinked to original sources

bioRxiv2025

Healthy adipocytes provide a protective environment by limiting viral infection through cell-cell communication

Adipocytes, long regarded primarily as energy storage cells, are increasingly recognized as active players in immune regulation. In metabolic disorders such as obesity and diabetes--conditions characterized by adipocyte dysfunction--patients often exhibit worsened outcomes following viral infections. However, the role of healthy adipocytes in modulating antiviral immunity remains poorly understood. Here, we demonstrate that healthy adipocytes secrete factors that confer antiviral protection to neighboring cells. We developed a fully human pluripotent stem cell (hPSC)-derived system including adipocytes, immune, and vascular cells to evaluate the antiviral capacity and infectivity of various cell types. Our cell system has the advantage of being of human origin, as opposed to animal models. Through our technological development, we have removed cell culture medium as a variable by adapting all cell types to a single base medium. We found that only adipocytes could induce an antiviral state in adjacent mural and immune cells. This unique immunomodulatory capacity is mediated, at least in part, by the STING-dependent secretion of low levels of interferon-alpha (IFN-) from healthy adipocytes. Notably, pharmacological induction of metabolic dysfunction in adipocytes diminished their antiviral activity, revealing a previously unrecognized link between metabolic health and antiviral defense. These findings identify a novel role for adipocytes in orchestrating local antiviral responses and provide new insight into how metabolic dysfunction may compromise host defense during viral infections.

cell biology↗

bioRxiv2025

Transcriptome-wide RNA accessibility mapping reveals structured RNA elements and pervasive conformational rearrangements under stress

RNA structure plays a central role in post-transcriptional gene regulation, modulating RNA stability, translation, and interactions with RNA-binding proteins (RBPs). However, capturing RNA conformations at scale remains challenging. Here, we introduce DMS-TRAM-seq (Dimethyl Sulfate-Transcriptome-wide RNA Accessibility Mapping by sequencing), which probes RNA structure across nearly the entire transcriptome. Using DMS-TRAM-seq, we generated secondary structure predictions for over 9,000 human transcripts, including hundreds of non-coding RNAs, and identified more than 700 previously unannotated, high-confidence structured elements. Importantly, the enhanced coverage provided by DMS-TRAM-seq enabled comparative analyses, revealing RNAs that undergo structural rearrangements in response to cellular perturbations. Integration with RBP motifs and ribosome profiling uncovered altered RNA-RBP interactions during oxidative stress and showed that translation inhibition broadly drives RNAs toward their thermodynamically favored conformations. DMS-TRAM-seq enables interrogation of the RNA structurome and its plasticity at an unprecedented scale, opening new directions for elucidating the structural basis of RNA regulation.

molecular biology↗

bioRxiv2025

A novel human blood-brain barrier model reveals pericytes as critical regulators of viral neuroinvasion

The blood-brain barrier (BBB) plays a vital role in regulating the passage of biomolecules between the bloodstream and the central nervous system (CNS) while also protecting the CNS from pathogens. Pericytes reside at the interface between the endothelial cells that form the vessel walls and the brain parenchyma. These cells are critical for maintaining BBB integrity and play key roles in regulating vessel permeability, blood flow, and immune cell migration. In this study, we developed a novel serum-free protocol to generate neural crest cell-derived pericytes (NCC-PCs) from human pluripotent stem cells (hPSCs). These NCC-PCs enhance BMEC barrier function and can be co-cultured with hPSC-derived brain microvascular endothelial cells (BMECs) in a contact co-culture BBB model that recapitulates the in vivo cellular interactions at the BBB. We used this model to evaluate the pathological consequences of BBB cell infection by highly neuroinvasive flaviviruses. Our results identify a previously undescribed role for NCC-PCs in maintaining BMEC barrier integrity during infection and reducing the spread of viral infection to the CNS.

microbiology↗

bioRxiv2024

Co-transcriptional splicing facilitates transcription of gigantic genes

Although introns are typically tens to thousands of nucleotides, there are notable exceptions. In flies as well as humans, a small number of genes contain introns that are more than 1000 times larger than typical introns, exceeding hundreds of kilobases (kb) to megabases (Mb). It remains unknown why gigantic introns exist and how cells overcome the challenges associated with their transcription and RNA processing. The Drosophila Y chromosome contains some of the largest genes identified to date: multiple genes exceed 4Mb, with introns accounting for over 99% of the gene span. Here we demonstrate that co-transcriptional splicing of these gigantic Y-linked genes is important to ensure successful transcription: perturbation of splicing led to the attenuation of transcription, leading to a failure to produce mature mRNA. Cytologically, defective splicing of the Y-linked gigantic genes resulted in disorganization of transcripts within the nucleus suggestive of entanglement of transcripts, likely resulting from unspliced long RNAs. We propose that co-transcriptional splicing maintains the length of nascent transcripts of gigantic genes under a critical threshold, preventing their entanglement and ensuring proper gene expression. Our study reveals a novel biological significance of co-transcriptional splicing.

developmental biology↗

bioRxiv2023

Targeted therapies prime oncogene-driven lung cancers for macrophage-mediated destruction

Macrophage immune checkpoint inhibitors, such as anti-CD47 antibodies, show promise in clinical trials for solid and hematologic malignancies. However, the best strategies to use these therapies remain unknown and ongoing studies suggest they may be most effective when used in combination with other anticancer agents. Here, we developed a novel screening platform to identify drugs that render lung cancer cells more vulnerable to macrophage attack, and we identified therapeutic synergy exists between genotype-directed therapies and anti-CD47 antibodies. In validation studies, we found the combination of genotype-directed therapies and CD47 blockade elicited robust phagocytosis and eliminated persister cells in vitro and maximized anti-tumor responses in vivo. Importantly, these findings broadly applied to lung cancers with various RTK/MAPK pathway alterations--including EGFR mutations, ALK fusions, or KRASG12C mutations. We observed downregulation of {beta}2-microglobulin and CD73 as molecular mechanisms contributing to enhanced sensitivity to macrophage attack. Our findings demonstrate that dual inhibition of the RTK/MAPK pathway and the CD47/SIRPa axis is a promising immunotherapeutic strategy. Our study provides strong rationale for testing this therapeutic combination in patients with lung cancers bearing driver mutations. Brief summaryUnbiased drug screens identify targeted therapies as drugs that make lung cancers with driver mutations more vulnerable to macrophage attack.

cancer biology↗

bioRxiv2021

Fragile X syndrome patient-derived neurons developing in the mouse brain show FMR1 -dependent phenotypes

Abnormal neuronal development in Fragile X syndrome (FXS) is poorly understood. Data on FXS patients remain scarce and FXS animal models have failed to yield successful therapies. In vitro models do not fully recapitulate the morphology and function of human neurons. Here, we co-injected neural precursor cells (NPCs) from FXS patient-derived and corrected isogenic control induced pluripotent stem cells into the brain of neonatal immune-deprived mice. The transplanted cells populated the brain and a proportion differentiated into neurons and glial cells. Single-cell RNA sequencing of transplanted cells revealed upregulated excitatory synaptic transmission and neuronal differentiation pathways in FXS neurons. Immunofluorescence analyses showed accelerated maturation of FXS neurons after an initial delay. Additionally, increased percentages of Arc- and Egr1-positive FXS neurons and wider dendritic protrusions of mature FXS striatal medium spiny neurons pointed to an increase in synaptic activity and synaptic strength as compared to control. This transplantation approach provides new insights into the alterations of neuronal development in FXS by facilitating physiological development of cells in a 3D context, and could be used to test new therapeutic compounds correcting neuronal development defects in FXS.

neuroscience↗

bioRxiv2018

Constrained mutational sampling of amino acids in HIV-1 protease evolution

The evolution of HIV-1 protein sequences should be governed by a combination of factors including nucleotide mutational probabilities, the genetic code, and fitness. The impact of these factors on protein sequence evolution are interdependent, making it challenging to infer the individual contribution of each factor from phylogenetic analyses alone. We investigated the protein sequence evolution of HIV-1 by determining an experimental fitness landscape of all individual amino acid changes in protease. We compared our experimental results to the frequency of protease variants in a publicly available dataset of 32,163 sequenced isolates from drug-naive individuals. The most common amino acids in sequenced isolates supported robust experimental fitness, indicating that the experimental fitness landscape captured key features of selection acting on protease during viral infections of hosts. Amino acid changes requiring multiple mutations from the likely ancestor were slightly less likely to support robust experimental fitness than single mutations, consistent with the genetic code favoring chemically conservative amino acid changes. Amino acids that were common in sequenced isolates were predominantly accessible by single mutations from the likely protease ancestor. Multiple mutations commonly observed in isolates were accessible by mutational walks with highly fit single mutation intermediates. Our results indicate that the prevalence of multiple base mutations in HIV-1 protease is strongly influenced by mutational sampling.

evolutionary biology↗