Biology subjects

Tan, T. L.

Publications and source records attributed to Tan, T. L..

3 recordsLinked to original sources

bioRxiv2026

Environmental Regulation and Gene-by-Environment Interaction Influence RAP1 Activity and its Impact on Gene Expression

Gene-by-environment (GxE) interactions play a major role in shaping both phenotypic and molecular variation, with important implications for human health and disease. In this study, we used the Doxycycline (Dox) regulated, tetracycline-responsive (Tet-Off) promoter system to sequentially reduce or titrate gene expression levels of the essential yeast transcription factor Repressor Activator Protein 1 (RAP1) similar to a hypomorph allele series, across three distinct environments: Yeast Peptone Dextrose (YPD) media, YPD media with Heat Shock (HS), and Yeast Peptone Acetate (YPAC) media. We then performed RNA sequencing (RNA Seq) to assess global transcriptional responses to RAP1 reduction in these different growth environments. Our analysis first focused on the independent effects of varying RAP1 expression levels within and across environments. We then explored GxE interactions, revealing a subset of genes with significant consequences of reduced levels of RAP1 and environment-specific expression patterns. Notably, many genes exhibited opposite effects of RAP1 titration on gene expression when yeast were grown in YPAC media compared to YPD media and/or HS, suggesting environment-dependent regulatory architecture. This design reveals how cells integrate internal transcriptional and regulatory changes with external environmental cues, providing a deeper view of GxE architecture. Using Weighted Gene Co-expression Network Analysis (WGCNA), we identified co-regulated gene modules, and by combining this with transcription factor motif enrichment tests, our study identified candidate regulators driving their dynamics. Our findings demonstrate that gene regulatory networks can vary dramatically depending on the environmental context an organism experiences, which can then influence the specific phenotypes produced by a particular genetic perturbation. This illustrates the complexity of genotype-environment interactions and the importance of studying gene function in multiple environments to gain a truly comprehensive understanding of a genes sometimes numerous and diverse functions.

genomics↗

bioRxiv2024

ER O-glycosylation in synovial fibroblasts drives cartilage degradation

How arthritic synovial fibroblasts (SFs) activate cartilage ECM degradation remains unclear. GALNT enzymes initiate O-glycosylation in the Golgi; when relocated to the ER, their activity stimulates ECM degradation. Here, we show that in human rheumatoid and osteoarthritic synovial SFs, GALNTs are relocated to the ER. In an RA mouse model, GALNTs relocation occurs shortly before arthritis symptoms and abates as the animal recovers. An ER GALNTs inhibitor prevents cartilage ECM degradation in vitro and expression of this chimeric protein in SFs results in the protection of cartilage. One of the ER targets of GALNTs is the resident protein Calnexin, which is exported to the cell surface of arthritic SFs. Calnexin participates in matrix degradation by reducing ECM disulfide bonds. Anti-Calnexin antibodies block ECM degradation and protect animals from RA. In sum, ER O-glycosylation is a key switch in arthritic SFs and glycosylated surface Calnexin could be a therapeutic target.

cell biology↗

bioRxiv2017

Rapid Detection of Sepsis using CESDA: the Caenorabditis elegans Sepsis Detection Assay

Sepsis is a life-threatening condition which could be alleviated by rapid diagnosis and appropriate antibiotic administration. However, currently available laboratory tests for sepsis diagnosis lacks sensitivity and specificity; they also have long turn-around times. In this proof-of-concept study, the nematode Caenorhabditis elegans was used as a biological sensor to detect urine of sepsis patients in an assay designated as the C. elegans Sepsis Detection Assay (CESDA). From January to June 2016, 45 patients who were admitted to the Emergency Department of a university hospital due to suspected sepsis were included into the study. Urine samples were obtained from these patients and healthy controls and spotted onto CESDA assay plates. Subsequently, C. elegans were aliquoted onto the centre of the plates and allowed to migrate freely. Number of worms found in either spots or quadrants of the plates containing control or suspected sepsis samples were scored in 10 minute intervals in a 60-minute duration. The CESDA index was then calculated for each sample, where an index near +1 represented attraction of the worms towards the sample, while an index near -1 signified repulsion. Confirmatory diagnosis for suspected sepsis samples was determined using a combination of clinical criteria assessment and standard laboratory protocols. All patients who were positive for sepsis were found to have a CESDA index of > 0.1 (positive predictive value, PPV [≥]87%). In addition, the worms were able to differentiate urine of sepsis patients from control as early as 20 minutes (p=0.012). Interestingly, the assay was also able to identify infection within 40 minutes of the test (AUROC = 0.80, p= 0.016). The rapidity of CESDA in sepsis and infection identification as well as the usability of urine samples which are non-invasive towards the patient in this method makes it an interesting protocol to be further explored for sepsis diagnosis.

microbiology↗