Biology subjects

Fallon, B. S.

Publications and source records attributed to Fallon, B. S..

2 recordsLinked to original sources

bioRxiv2023

Discovery and Validation of Context-Dependent Synthetic Mammalian Promoters

Cellular transcription enables cells to adapt to various stimuli and maintain homeostasis. Transcription factors bind to transcription response elements (TREs) in gene promoters, initiating transcription. Synthetic promoters, derived from natural TREs, can be engineered to control exogenous gene expression using endogenous transcription machinery. This technology has found extensive use in biological research for applications including reporter gene assays, biomarker development, and programming synthetic circuits in living cells. However, a reliable and precise method for selecting minimally-sized synthetic promoters with desired background, amplitude, and stimulation response profiles has been elusive. In this study, we introduce a massively parallel reporter assay library containing 6184 synthetic promoters, each less than 250 bp in length. This comprehensive library allows for rapid identification of promoters with optimal transcriptional output parameters across multiple cell lines and stimuli. We showcase this librarys utility to identify promoters activated in unique cell types, and in response to metabolites, mitogens, cellular toxins, and agonism of both aminergic and non-aminergic GPCRs. We further show these promoters can be used in luciferase reporter assays, eliciting 50-100 fold dynamic ranges in response to stimuli. Our platform is effective, easily implemented, and provides a solution for selecting short-length promoters with precise performance for a multitude of applications.

synthetic biology↗

bioRxiv2022

Clinical and In Situ Characterization of Hepatitis Delta Virus in Sjogren's Syndrome

Hepatitis delta virus (HDV) has been detected in the minor salivary gland (MSG) tissue of Sjogrens Syndrome (SjS) patients in the absence of an HBV co-infection. HDV antigen expression was previously shown to trigger an SjS-like phenotype in vivo, demonstrating a cause-and-effect association. We hypothesize that if HDV regulates SjS development, then HDV profiles may correlate with disease manifestations. This retrospective study characterized HDV in a cohort of 48 SjS MSG between 2014-2021. Analyses of HDV antigen (HDAg) expression, including cell type and subcellular localization, in situ hybridization of HDV RNA, and comparative analyses with associated SjS and viral hepatitis clinical features were conducted. HDAg was detected in MSG acinar, ductal, and adipose cells. HDAg localized with nuclei and mitochondria. HDV genomic RNA localized to the nucleus. A significant negative correlation was noted between HDAg intensity and focal lymphocytic inflammation. No significant associations were detected between MSG-localized HDAg and liver enzymes, or an evident HBV co-infection. This study has identified a non-hepatic reservoir for chronic HDV persistence in SjS-affected MSG and a unique mitochondrial localization for HDV antigen. Detection of non-hepatic HDV-mediated disease in the absence of an evident current or past HBV co-infection warrants further investigation.

microbiology↗