Biology subjects

Barth, J. L.

Publications and source records attributed to Barth, J. L..

7 recordsLinked to original sources

bioRxiv2026

A Novel Central-Peripheral Interface: The Auditory Nerve Glial Transition Zone Exhibits Enhanced Age-Related Immune and Glial Cell Dysfunction

Age-related hearing loss (ARHL) is a rapidly growing public health concern, affecting two-thirds of adults over 65 years old, with no effective therapeutics available. As the aging population grows at an unprecedented rate, the burden of ARHL will only increase. The causes of ARHL are multifactorial, but an understudied major contributor is glial dysfunction. The auditory nerve (AN) conducts sound from the cochlea to the brainstem and holds a diverse population of immune cells and myelinating glia. As the AN fibers bundle together within the cochlea to project to the brainstem, they are first myelinated by Schwann cells in the peripheral AN, then myelinated by oligodendrocytes in the central AN. The region where myelination shifts from Schwann cells to oligodendrocytes is the glial transition zone (GTZ), located in the cochlear modiolus, creating a unique biological niche. While central-peripheral interfaces are recognized in other cranial nerves, the AN GTZ is understudied. This region integrates the peripheral and central microenvironments within the confined bony cochlea, positioning it as a niche for glial dysfunction in pathological conditions, such as aging. We hypothesize that the GTZ is a site of enhanced glial dysfunction contributing to age-related AN demyelination, an important contributor to ARHL. We evaluated this in an ARHL mouse model combining RNA-sequencing, quantitative immunohistochemistry, and 3D high-resolution imaging. We examined the AN GTZ from human temporal bone donors. RNA-sequencing of the AN revealed age-associated increases in abnormal myelination/glial function and inflammation. There was a significant age-dependent increase in Iba1+ macrophages/microglia, with accumulation at the AN GTZ, and an increase in cellular volume and surface area, suggesting greater age-related activation. Macrophages/microglia contained significantly more internalized myelin debris in the AN (peripheral, central, and GTZ) with aging. More importantly, we found structurally intact myelin within macrophages/microglia only at the GTZ, suggesting a unique microenvironment at the GTZ altering phagocytic activity in aging. Together, our data suggest that the GTZ, a previously unrecognized central-peripheral interface, is a critical site of immune-glial interactions and especially vulnerable to age-related demyelination and neuroinflammation. This study highlights the GTZ as a potential target for preserving AN myelination and mitigating ARHL.

neuroscience↗

bioRxiv2023

Immune Responses in Checkpoint Myocarditis Across Heart, Blood, and Tumor

Immune checkpoint inhibitors (ICIs) are widely used anti-cancer therapies that can cause morbid and potentially fatal immune-related adverse events (irAEs). ICI-related myocarditis (irMyocarditis) is uncommon but has the highest mortality of any irAE. The pathogenesis of irMyocarditis and its relationship to anti-tumor immunity remain poorly understood. We sought to define immune responses in heart, tumor, and blood during irMyocarditis and identify biomarkers of clinical severity by leveraging single-cell (sc)RNA-seq coupled with T cell receptor (TCR) sequencing, microscopy, and proteomics analysis of 28 irMyocarditis patients and 23 controls. Our analysis of 284,360 cells from heart and blood specimens identified cytotoxic T cells, inflammatory macrophages, conventional dendritic cells (cDCs), and fibroblasts enriched in irMyocarditis heart tissue. Additionally, potentially targetable, pro-inflammatory transcriptional programs were upregulated across multiple cell types. TCR clones enriched in heart and paired tumor tissue were largely non-overlapping, suggesting distinct T cell responses within these tissues. We also identify the presence of cardiac-expanded TCRs in a circulating, cycling CD8 T cell population as a novel peripheral biomarker of fatality. Collectively, these findings highlight critical biology driving irMyocarditis and putative biomarkers for therapeutic intervention.

immunology↗

bioRxiv2023

Therapy-associated remodeling of pancreatic cancer revealed by single-cell spatial transcriptomics and optimal transport analysis

In combination with cell intrinsic properties, interactions in the tumor microenvironment modulate therapeutic response. We leveraged high-plex single-cell spatial transcriptomics to dissect the remodeling of multicellular neighborhoods and cell-cell interactions in human pancreatic cancer associated with specific malignant subtypes and neoadjuvant chemotherapy/radiotherapy. We developed Spatially Constrained Optimal Transport Interaction Analysis (SCOTIA), an optimal transport model with a cost function that includes both spatial distance and ligand-receptor gene expression. Our results uncovered a marked change in ligand-receptor interactions between cancer-associated fibroblasts and malignant cells in response to treatment, which was supported by orthogonal datasets, including an ex vivo tumoroid co-culture system. Overall, this study demonstrates that characterization of the tumor microenvironment using high-plex single-cell spatial transcriptomics allows for identification of molecular interactions that may play a role in the emergence of chemoresistance and establishes a translational spatial biology paradigm that can be broadly applied to other malignancies, diseases, and treatments.

cancer biology↗

bioRxiv2022

Peripheral Auditory Nerve Impairment in a Mouse Model of Syndromic Autism

Dysfunction of the peripheral auditory nerve (AN) contributes to dynamic changes throughout the central auditory system, resulting in abnormal auditory processing, including hypersensitivity. Altered sound sensitivity is frequently observed in autism spectrum disorder (ASD), suggesting that AN deficits and changes in auditory information processing may contribute to ASD-associated symptoms, including social communication deficits and hyperacusis. The MEF2C transcription factor is associated with risk for several neurodevelopmental disorders, and mutations or deletions of MEF2C produce a haploinsufficiency syndrome characterized by ASD, language and cognitive deficits. A mouse model of this syndromic ASD (i.e., Mef2c+/- or Mef2c-Het) recapitulates many of the MEF2C Haploinsufficiency syndrome-linked behaviors including communication deficits. We show here that Mef2c-Het mice exhibit functional impairment of the peripheral AN and a modest reduction in hearing sensitivity. We find that MEF2C is expressed during development in multiple AN and cochlear cell types, and in Mef2c-Het mice, we observe multiple cellular and molecular alterations associated with the AN, including abnormal myelination, neuronal degeneration, neuronal mitochondria dysfunction, and increased macrophage activation and cochlear inflammation. These results reveal the importance of MEF2C function in inner ear development and function and the engagement of immune cells and other non-neuronal cells, which suggests that microglia/macrophages and other non-neuronal cells might contribute, directly or indirectly, to AN dysfunction and ASD-related phenotypes. Finally, our study establishes a comprehensive approach for characterizing AN function at the physiological, cellular, and molecular levels in mice, which can be applied to animal models with a wide range of human auditory processing impairments. Significance StatementThis is the first report of peripheral auditory nerve (AN) impairment in a mouse model of human MEF2C haploinsufficiency syndrome that has well-characterized ASD related behaviors including communication deficits, hyperactivity, repetitive behavior, and social deficits. We identify multiple underlying cellular, sub-cellular, and molecular abnormalities that may contribute to peripheral AN impairment. Our findings also highlight the important roles of immune cells (e.g., cochlear macrophages) and other non-neuronal elements (e.g., glial cells and cells in the stria vascularis) in auditory impairment in ASD. The methodological significance of the study is the establishment of a comprehensive approach for evaluating peripheral AN function and impact of peripheral AN deficits with minimal hearing loss.

neuroscience↗

bioRxiv2021

Structural and functional analysis of lorlatinib analogs reveals roadmap for targeting diverse compound resistance mutations in ALK-positive lung cancer

The treatment approach to advanced, ALK-positive non-small cell lung cancer (NSCLC) utilizing sequential ALK tyrosine kinase inhibitors (TKIs) represents a paradigm of precision oncology. Lorlatinib is currently the most advanced, potent and selective ALK tyrosine kinase inhibitor (TKI) in the clinic. However, tumors invariably acquire resistance to lorlatinib, and after sequential ALK TKIs culminating with lorlatinib, diverse refractory compound ALK mutations can emerge. Here, we determine the spectrum of lorlatinib-resistant compound ALK mutations identified in patients after treatment with lorlatinib, the majority of which involve ALK G1202R or I1171N/S/T. By assessing a panel of lorlatinib analogs against compound ALK mutant in vitro and in vivo models, we identify structurally diverse lorlatinib analogs that harbor differential selective profiles against G1202R- versus I1171N/S/T-based compound ALK mutations. Structural analysis revealed that increased potency against compound mutations was achieved primarily through two different mechanisms of improved targeting of either G1202R- or I1171N/S/T-mutant kinases. Based on these results, we propose a classification of heterogenous ALK compound mutations designed to focus the development of distinct therapeutic strategies for precision targeting of compound resistance mutations following sequential TKIs.

cancer biology↗

bioRxiv2021

Two distinct types of nodes of Ranvier support auditory nerve function in the mouse cochlea

Glial cells of the auditory nerve regulate formation of the nodes of Ranvier that are needed for regeneration of action potentials and proper hearing function. Here we identify and describe the distinct features of two novel types of Ranvier nodes--the axonal node and the ganglion node--in the mouse auditory nerve that change across the lifespan, including during myelination and postnatal development, and degenerate during aging. Cellular, molecular, and structure-function correlation evaluations revealed that nodal types are critical for different aspects of auditory nerve function. Specifically, the length of the axonal node is associated with neural processing speed and neural synchrony, whereas ganglion node development is associated with amplitude growth of the action potential. Moreover, our data indicate that dysregulation of glial cells and associated degeneration of the ganglion node structure are an important and new mechanism of auditory nerve dysfunction in age-related hearing loss.

neuroscience↗

bioRxiv2018

Transcriptomic characterization of signaling pathways associated with osteoblastic differentiation of MC-3T3E1 cells

Bone remodeling involves the coordinated actions of osteoclasts, which resorb the calcified bony matrix, and osteoblasts, which refill erosion pits created by osteoclasts to restore skeletal integrity and adapt to changes in mechanical load. Osteoblasts are derived from pluripotent mesenchymal stem cell precursors, which undergo differentiation under the influence of a host of local and environmental cues. To characterize the autocrine/paracrine signaling networks associated with osteoblast maturation and function, we performed gene network analysis using complementary \"agnostic\" DNA microarray and \"targeted\" NanoString nCounter datasets derived from murine MC3T3-E1 cells induced to undergo synchronized osteoblastic differentiation in vitro. Pairwise datasets representing changes in gene expression associated with growth arrest (day 2 to 5 in culture), differentiation (day 5 to 10 in culture), and osteoblast maturation (day 10 to 28 in culture) were analyzed using Ingenuity Systems Pathways Analysis to generate predictions about signaling pathway activity based on the temporal sequence of changes in target gene expression. Our data indicate that some pathways known to be involved in osteoblast differentiation, e.g. Wnt/{beta}-catenin signaling, are most active early in the process, while others, e.g. TGF{beta}/BMP, cytokine/JAK-STAT and TNF/RANKL signaling, increase in activity as differentiation progresses. Collectively, these pathways contribute to the sequential expression of genes involved in the synthesis and mineralization of extracellular matrix. These results provide insight into the temporal coordination and complex interplay between signaling networks controlling gene expression during osteoblast differentiation. A more complete understanding of these processes may aid the discovery of novel methods to promote osteoblast development for the treaent of conditions characterized by low bone mineral density.

cell biology↗