Biology subjects

Li, T. Y.

Publications and source records attributed to Li, T. Y..

5 recordsLinked to original sources

bioRxiv2026

BioTrajX: evaluating biological plausibility in single-cell trajectory inference

Trajectory inference (TI) methods reconstruct cellular progression from single-cell RNA sequencing data, typically by ordering cells along a pseudotime axis. However, different TI methods and analytical choices can produce divergent trajectories from the same dataset, making it difficult to determine which inferred trajectory best reflects the underlying biological process. Existing evaluation strategies often rely on computational benchmarks or qualitative biological assessment, with limited standardized approaches for incorporating a priori biological knowledge. Here, we present BioTrajX, an R package for biologically informed evaluation of pseudotime trajectories using three complementary metrics: Directionality (D), which measures agreement between pseudotime and expected biological progression; Order Consistency (O), which quantifies the coherence of marker-program changes along the trajectory; and Endpoint Validity (E), which assesses enrichment of expected cell states at trajectory endpoints. Together, the DOE metrics provide an interpretable framework for comparing alternative trajectory inference results and evaluating root-cell choices prior to downstream analyses.

bioinformatics↗

bioRxiv2022

Lysosomes mediate the mitochondrial UPR via mTORC1-dependent ATF4 phosphorylation

Lysosomes are central platforms for not only the degradation of macromolecules but also the integration of multiple signaling pathways. However, whether and how lysosomes mediate the mitochondrial stress response (MSR) remain largely unknown. Here, we demonstrate that lysosomal acidification via the vacuolar H+-ATPase (v-ATPase) is essential for the transcriptional activation of the mitochondrial unfolded protein response (UPRmt). Mitochondrial stress stimulates v-ATPase-mediated lysosomal activation of the mechanistic target of rapamycin complex 1 (mTORC1), which then directly phosphorylates the MSR transcription factor, activating transcription factor 4 (ATF4). Disruption of mTORC1-dependent ATF4 phosphorylation blocks the UPRmt, but not other similar stress responses, such as the UPRER. Finally, ATF4 phosphorylation downstream of the v-ATPase/mTORC1 signaling is indispensable for sustaining mitochondrial redox homeostasis and protecting cells from reactive oxygen species (ROS)-associated cell death upon mitochondrial stress. Thus, v-ATPase/mTORC1-mediated ATF4 phosphorylation via lysosomes links mitochondrial stress to UPRmt activation and mitochondrial function resilience.

cell biology↗

bioRxiv2022

A lysosomal surveillance response (LySR) that reduces proteotoxicity and extends healthspan

Lysosomes are cytoplasmic organelles central for the degradation of macromolecules to maintain cellular homeostasis and health. Here, we discovered an adaptive lysosomal transcriptional response that we termed the Lysosomal Surveillance Response (LySR). Typified by the induction of a large group of transcripts involved in lysosomal function and proteolysis, the LySR can be triggered by silencing of specific vacuolar H+-ATPase subunits in Caenorhabditis elegans. Notably, LySR activation enhances the clearance of protein aggregates in worm models of Alzheimers and Huntingtons disease and amyotrophic lateral sclerosis, thereby boosting fitness and extending lifespan. The GATA transcription factor, ELT-2, regulates the LySR program as well as its associated beneficial effects. In mammalian cells, overexpression of GATA4/GATA6, the mammalian orthologs of ELT-2, is sufficient to induce the expression of multiple lysosome-specific proteases and alleviate proteotoxicity. Activating the LySR pathway may therefore represent an attractive mechanism to reduce proteotoxicity and, as such, potentially extend healthspan. HighlightsO_LIRNAi of specific v-ATPase subunits extends C. elegans lifespan and activates LySR C_LIO_LIGATA transcription factor ELT-2 regulates LySR and LySR-associated lifespan extension C_LIO_LILySR activation reduces protein aggregates and extends worm healthspan C_LIO_LIOverexpression of GATA4/GATA6 alleviates amyloid-{beta} proteotoxicity in mammalian cells C_LI

cell biology↗

bioRxiv2021

Multi-omics analysis identifies essential regulators of mitochondrial stress response in two wild-type C. elegans strains

The mitochondrial unfolded protein response (UPRmt) is a promising pharmacological target for aging and age-related diseases. However, the integrative analysis of the impact of UPRmt activation on different layers of signaling in animals with a different genetic background is lacking. In this study, we applied systems approaches to investigate the effect of UPRmt induced by administering doxycycline (Dox) on transcriptome, proteome, lipidome, and metabolome in two genetically divergent C. elegans strains. We found that Dox prolongs lifespan of both worm strains through pathways in both shared and strain-specific manners. From the integrated omics datasets, we observed a strong impact of Dox on mitochondrial functions, detected upregulated defense response and lipid metabolism, identified decreased triglycerides and lowered metabolome profiles in both strains. This conserved phenomic footprint has great translational value as it indicates that the beneficial effects of Dox-induced UPRmt on health and lifespan are consistent across different genetic backgrounds.

systems biology↗

bioRxiv2019

Identifying gene function and module connections by the integration of multi-species expression compendia

The functions of many eukaryotic genes are still poorly understood. We developed and validated a new method, termed GeneBridge, which is based on two linked approaches to impute gene function and bridge genes with biological processes. First, Gene-Module Association Determination (G-MAD) allows the annotation of gene function. Second, Module-Module Association Determination (M-MAD) allows predicting connectivity among modules. We applied the GeneBridge tools to large-scale multi-species expression compendia--1,700 datasets with over 300,000 samples from human, mouse, rat, fly, worm, and yeast--collected in this study. Unlike most existing bioinformatics tools, GeneBridge exploits both positive and negative gene/module-module associations. We constructed association networks, such as those bridging mitochondria and proteasome, mitochondria and histone demethylation, as well as ribosomes and lipid biosynthesis. The GeneBridge tools together with the expression compendia are available at systems-genetics.org, to facilitate the identification of connections linking genes, modules, phenotypes, and diseases.

systems biology↗