Abstract

Type 1 diabetes (T1D) is an autoimmune disease characterized by hyperglycemia due to the loss of insulin-producing pancreatic β cells. With over 70 associated genetic loci identified, T1D is known to have a strong genetic component, but a high discordance rate in identical twins suggests a critical role for environmental factors. Coxsackievirus B (CVB) infection has long been implicated as a potential environmental trigger for T1D. Meanwhile, genome-wide association studies have identified IFIH1, a gene that encodes the viral sensor MDA5, as a key susceptibility locus. Notably, different single nucleotide polymorphisms (SNPs) within IFIH1 have been associated with either increased risk or protection. However, due to the scarcity of high-quality cadaveric islets of Langerhans from T1D patients, their heterogeneous nature, and technological limitations, the interplay between these genetic factors and environmental stressors in a human pancreatic context has been difficult to study. This dissertation addresses these critical knowledge gaps by investigating the cellular and genetic factors that govern islet response to stress using advanced human islet models and single-cell sequencing technologies. The first chapter provides a general overview of T1D as an autoimmune disease, key immune-associated T1D susceptibility genes, enteroviral infection as a potential environmental trigger, and the use of human pluripotent stem cells (hPSCs) for disease modeling. In the second chapter, we hypothesized that CVB3 infection induces unique cell-type-specific transcriptional responses in primary human islets. We used single-cell RNA sequencing (scRNA-seq) to show that CVB3 infects all cell types within primary human islets at a similar rate, contrary to prior claims based on viral protein staining. We found that insulin-secreting β, glucagon-secreting α, and ductal cells exhibit the most robust transcriptional responses to viral infection, with ductal cells showing the strongest interferon-stimulated response. CVB3 infection also induced mitochondrial dysfunction, with differential effects on mitochondrial size in β and α cells. Our dataset also identified the long non-coding RNA, MIR7-3HG, as a key regulator of viral titer, apoptosis, and autophagy upon genetic knockdown in stem cell-derived islets (SC-islets). The third chapter of this thesis investigated how specific IFIH1 SNPs impact islet health and stress response. We hypothesized that the protective MDA5627* variant protects islet cells against stress-mediated dysfunction, identity loss, and cell death compared to the at-risk MDA5946T variant. Using SC-islets generated from CRISPR-Cas9-edited hPSCs derived from a T1D patient, our scRNA-seq analysis demonstrated unique, cell-type-specific transcriptional responses to inflammatory and viral stress that varied across the MDA5 variants. Our data showed the MDA5627* variant dampened the stress-mediated immune response and mitochondrial dysfunction, while also improving insulin secretion, reducing apoptosis rates, and lowering viral genome expression in SC-islets. Overall, this dissertation provides a comprehensive overview of cell-specific responses in both primary human islets and SC-islets following viral and inflammatory stress. We characterized the roles of key candidate genes and clinically relevant variants in promoting islet health. The insights gained from these studies broaden our understanding of the connection between genetic variation, environmental factors, and islet health in humans, providing a crucial foundation for developing strategies to prevent or delay T1D initiation and progression in genetically susceptible individuals.

Committee Chair

Jeffrey Millman

Committee Members

Brian Clark; Fumihiko Urano; Hubert Tse; Jeffrey Millman; Jing Hughes

Degree

Doctor of Philosophy (PhD)

Author's Department

Biology & Biomedical Sciences (Developmental, Regenerative, & Stem Cell Biology)

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

12-18-2025

Language

English (en)

Author's ORCID

0000-0002-0844-2343

Download

Available for download on Friday, December 17, 2027

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Biology Commons

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