Biology subjects

Bradley, K.

Publications and source records attributed to Bradley, K..

3 recordsLinked to original sources

bioRxiv2025

Protective IFIH1 variant reduces immune-mediated islet stress and dysfunction in a type 1 diabetes genetic background

Genome-wide association studies (GWAS) have linked dozens of genetic loci to type 1 diabetes (T1D). The IFIH1 gene, which encodes the double-stranded RNA sensor MDA5, is one such locus. The E627* single nucleotide polymorphism (SNP) in IFIH1 is associated with protection against T1D, while the A946T variant is linked to increased risk. While the E627* variant has been shown to result in a truncated protein and dampen type I interferon (IFN) signaling, its specific role in human pancreatic islet health and function remains unclear. We hypothesized that MDA5627* would protect islet cells from stress-induced dysfunction, identity loss, and cell death. Using CRISPR-Cas9 technology, we introduced the E627* and A946T variants into human pluripotent stem cells (hPSCs) derived from a T1D patient. We differentiated these hPSCs into stem cell-derived islets (SC-islets) and treated them with IFN, poly(I:C), and coxsackievirus B3, an enterovirus implicated in T1D pathogenesis. Using single-cell RNA sequencing and an array of functional assays, we investigated the variant impact on both whole SC-islets and their individual cell populations. Our analysis revealed that SC-islets, and their {beta}, , and {delta} cell subpopulations, harboring the MDA5627* variant exhibit an attenuated immune response to the various stressors compared to MDA5946T cells. We also report unique, cell-type-specific transcriptional responses that vary across variants. Notably, MDA5627* SC-islets showed reduced apoptosis rates and viral genome expression, as well as attenuated negative effects on mitochondrial function and insulin secretion in response to stress. Overall, our findings demonstrate that a clinically relevant MDA5 variant confers protection by dampening stress-mediated transcriptional responses, reducing cell dysfunction, and preventing apoptosis. These insights provide a mechanistic framework for understanding T1D pathogenesis and offer new avenues for developing preventative therapies.

cell biology↗

bioRxiv2025

C. elegans astrocytes mature in two phases from lineally distinct progenitors through CEH-43/DLX-mediated convergent transcription

Mammalian radial glia can remodel to become astrocytes, which acquire common transcriptional states despite spatially and lineally distinct origins. To uncover molecular programs driving convergent radial-glia-to-astrocyte transformation, we investigated development of C. elegans CEPsh astrocytes, which also arise from distinct progenitors without cell division. Using lineage-restricted single-cell RNA sequencing, we delineate a two-phase program for CEPsh astrocyte formation. Transcriptionally disparate nascent CEPsh glia rapidly acquire a common radial-glia-like state, facilitating nerve ring (brain) assembly. Subsequently, convergent CEPsh glia upregulate astrocyte-specific gene expression. Both phases require the distal-less transcription factor CEH-43, expressed in CEPsh glia and their progenitors. CEH-43 binds conserved astrocyte-expressed genes, cell-autonomously activating both early and late CEPsh glia-specific gene expression. CEH-43 misexpression is sufficient to induce CEPsh astrocyte reporter expression. We demonstrate that CEH-43 homologs, DLX1/2, are expressed in mouse astrocytes, and comparative transcriptomics reveal additional parallels. Our findings provide a molecular foundation for understanding cell-division-independent radial-glia-to-astrocyte transformation.

neuroscience↗

bioRxiv2025

Divergent Cell-Type Specific Hypoxia Responses in Human Stem Cell-Derived and Primary Islets

BackgroundThe success of stem cell-derived islet (SC-islet) therapy for type 1 diabetes is limited by poor graft survival in the hypoxic post-transplantation microenvironment. While the response of SC-islets to chronic hypoxia has been studied, a direct comparison to primary human islets during the acute hypoxic phase has not been performed. Here, we conduct a comparative single-cell transcriptomic and functional analysis of human SC-islets and primary islets exposed to acute hypoxia (1% O2) over 48 hours. ResultsOur analysis reveals two divergent response patterns. Primary islets exhibit an energy-conserving response, characterized by a {beta}-cell-specific suppression of identity genes (PDX1, MAFA) and pro-apoptotic factors like DDIT3, alongside a shift toward metabolic quiescence. In contrast, the SC-islet response is characterized by lineage instability, a significant metabolic shift toward glycolysis, and the activation of pro-apoptotic pathways. Functionally, these transcriptomic differences result in a loss of glucose-stimulated insulin secretion in both islet types, but through different mechanisms: a suppression of secretion in primary islets versus dysregulated, glucose-unresponsive insulin release in SC-islets. ConclusionThese findings demonstrate that SC-islets are particularly vulnerable under hypoxic stress, exhibiting an unstable, plastic phenotype. This comparative dataset provides a resource for developing source-specific therapeutic interventions to overcome the hypoxic barrier and improve the efficacy of cell replacement therapies.

cell biology↗