Biology subjects

Parker, A. C.

Publications and source records attributed to Parker, A. C..

4 recordsLinked to original sources

bioRxiv2025

Closing the loop: Teaching single-cell foundation models to learn from perturbations

The application of transfer learning models to large scale single-cell datasets has enabled the development of single-cell foundation models (scFMs) that can predict cellular responses to perturbations in silico. Although these predictions can be experimentally tested, current scFMs are unable to "close the loop" and learn from these experiments to create better predictions. Here, we introduce a "closed-loop" framework that extends the scFM by incorporating perturbation data during model fine-tuning. Our closed-loop model improves prediction accuracy, increasing positive predictive value in the setting of T-cell activation three-fold. We applied this model to RUNX1-familial platelet disorder, a rare pediatric blood disorder and identified two therapeutic targets (mTOR and CD74-MIF signaling axis) and two novel pathways (protein kinase C and phosphoinositide 3-kinase). This work establishes that iterative incorporation of experimental data to foundation models enhances biological predictions, representing a crucial step toward realizing the promise of "virtual cell" models for biomedical discovery.

bioinformatics↗

bioRxiv2024

Novel roles for pirin proteins and a 2-ketoglutarate:ferredoxin oxidoreductase ortholog in Bacteroides fragilis central metabolism and comparison of metabolic mutants susceptibility to antimicrobials metronidazole and amixicile.

The regulation of the central metabolism and fermentation pathways and its effect on antimicrobial susceptibility in the anaerobic pathogen Bacteroides fragilis is not completely understood. In this study we show that B. fragilis encodes for two iron-dependent redox-sensitive regulatory pirin protein genes, pir1 and pir2, whose mRNA expression are upregulated following oxygen exposure and growth in iron-limiting conditions.{Delta} pir1 and{Delta} pir2 mutants showed altered short-chain fatty acids production compared to the parent strain. Overexpression of Pir1 and Pir2 increased susceptibility to metronidazole (MTZ), and to amixicile (AMIX), a novel inhibitor of pyruvate:ferredoxin oxidoreductase (PFOR) in anaerobes. We hypothesized these observations were a result of a modulatory effect of Pir1 and Pir2 proteins. Consistent with this, we showed that Pir1 forms direct protein-protein interactions with PFOR. In addition, AlphaFold2-based structural analysis predicts that Pir1 and Pir2 form stable interactions with several enzymes of the central metabolism including the 2-ketoglutate:ferredoxin oxidoreductases (KFOR), Kor1AB and Kor2CDAEBG. A series of metabolic mutants and electron transport chain inhibitors were used to show a wide-ranging effect of bacterial metabolism on MTZ and AMIX susceptibility. There was no cross-resistance between MTZ resistant strains with AMIX susceptibility. Furthermore, we show that AMIX is an effective antimicrobial against B. fragilis in an experimental model of intra-abdominal infection. This investigation led to the discovery that the kor2AEBG genes are essential for growth, and we present evidence that kor2AEBG genes have dual-functions including the reductive synthesis of 2-ketoglutarate via reverse TCA cycle. Support for a novel Kor2AEBG activity comes from the findings showing that addition of compounds containing oleic acid stimulated growth of the{Delta} kor2AEBG mutant. However, the metabolic activity that bypasses KorAEBG function remains to be defined. Collectively our investigation reveals new information on B. fragilis central metabolism and its modulatory control by pirin proteins. These data provide new genetic and metabolic knowledge which may be leveraged for the future development of new narrow-spectrum antimicrobials.

microbiology↗

bioRxiv2022

Mutated cells mediate distinct inflammatory responses in clonal hematopoiesis

Clonal hematopoiesis (CH) is an age-associated phenomenon that increases risk for hematologic malignancy and cardiovascular disease. CH is thought to enhance disease risk through inflammation in the peripheral blood1. Here, we profile peripheral blood gene expression in 66,968 single cells from a cohort of 17 CH patients and 7 controls. Using a novel mitochondrial DNA barcoding approach, we were able to identify and separately compare mutant TET2 and DNMT3A cells to non-mutant counterparts. We discovered the vast majority of mutated cells were in the myeloid compartment. Additionally, patients harboring DNMT3A and TET2 CH mutations possessed a pro-inflammatory profile in CD14+ monocytes through previously unrecognized pathways such as galectin and macrophage Inhibitory Factor (MIF). We also found that T cells from CH patients, though mostly un-mutated, had decreased expression of GTPase of the immunity associated protein (GIMAP) genes, which are critical to T cell development, suggesting that CH may impair T cell function. Key points- CD14+ monocytes from clonal hematopoiesis patients stimulate inflammation through increased cytokine expression. - T cells from clonal hematopoiesis are deficient in GIMAP expression, suggesting CH may impair T cell differentiation.

genetics↗

bioRxiv2021

The DNA methylation landscape of five pediatric-tumor types

Fewer DNA mutations have been identified in pediatric tumors than adult tumors, suggesting that alternative tumorigenic mechanisms, including aberrant DNA methylation, may play a prominent role in pediatric tumors. Methylation is an epigenetic process of regulating gene expression in which methyl groups are attached to DNA molecules, often in promoter regions. In Wilms tumors and acute myeloid leukemias, increased levels of epigenetic silencing have been associated with worse patient outcomes. However, to date, researchers have studied methylation primarily in adult tumors and for specific genes but not on a pan-pediatric cancer scale. We addressed these gaps first by aggregating methylation data from 309 noncancerous samples and establishing baseline expectations for each gene. Even though these samples represent diverse tissue types and population ancestral groups, methylation levels were highly consistent for most genes. Second, we compared tumor methylation levels against these baseline values for five pediatric cancer types--Wilms tumors, clear cell sarcomas of the kidney, rhabdoid tumors, neuroblastomas, and osteosarcomas. Hypermethylation was more common than hypomethylation--as many as 11.8% of genes were hypermethylated in a given tumor, compared to a maximum of 4.8% for hypomethylated genes. For each cancer type, genes with the highest variance exhibited consistently divergent methylation patterns for distinct patient subsets. We evaluated whether genomic and epigenomic abnormalities contribute to pediatric tumorigenesis in a mutually exclusive manner but did not find evidence of this phenomenon. Furthermore, even though oncogenes are commonly upregulated in tumors, and tumor-suppressor genes are commonly downregulated in tumors, we did not find statistical evidence that methylation drives such patterns on a broad scale in pediatric tumors.

genomics↗