Biology subjects

Wong, L. H.

Publications and source records attributed to Wong, L. H..

3 recordsLinked to original sources

bioRxiv2021

Massively parallel characterization of CYP2C9 variant enzyme activity and abundance

CYP2C9 encodes a cytochrome P450 enzyme responsible for metabolizing up to 15% of small molecule drugs, and CYP2C9 variants can alter the safety and efficacy of these therapeutics. In particular, the anti-coagulant warfarin is prescribed to over 15 million people annually and polymorphisms in CYP2C9 can affect patient response leading to an increased risk of hemorrhage. We developed Click-seq, a pooled yeast-based activity assay to test thousands of variants. Using Click-seq, we measured the activity of 6,142 missense variants expressed in yeast. We also measured the steady-state cellular abundance of 6,370 missense variants expressed in a human cell line using Variant Abundance by Massively Parallel sequencing (VAMP-seq). These data revealed that almost two-thirds of CYP2C9 variants showed decreased activity, and that protein abundance accounted for half of the variation in CYP2C9 function. We also measured activity scores for 319 previously unannotated human variants, many of which may have clinical relevance.

genomics↗

bioRxiv2021

Cholesteryl Hemiazelate Induces Lysosome Dysfunction and Exocytosis in Macrophages

OBJECTIVEA key event in atherogenesis is the formation of lipid-loaded macrophages, lipidotic cells, which exhibit irreversible accumulation of undigested modified low-density lipoproteins in lysosomes. This event culminates with the loss of cell homeostasis, inflammation and cell death. In this study we propose to identify the chemical etiological factors and understanding the molecular and cellular mechanisms responsible for the impairment of lysosome function in macrophages. APPROACH AND RESULTSUsing shotgun lipidomics we have discovered that a family of oxidized lipids (cholesteryl hemiesters, ChE), end products of oxidation of polyunsaturated cholesteryl esters, occurs at higher concentrations in the plasma of two cohorts of cardiovascular disease patients than in the plasma of a control cohort. Macrophages exposed to the most prevalent ChE, cholesteryl hemiazelate (ChA) exhibit lysosome enlargement, peripheral lysosomal positioning, lysosome dysfunction and lipidosis which are irreversible. The transcriptomic profile of macrophages exposed to ChA indicates that the lysosome pathway is deeply affected and is well correlated with lysosome phenotypic and functional changes. Interestingly, the dysfunctional peripheral lysosomes are more prone to fuse with the plasma membrane, secreting their undigested luminal content into the extracellular milieu with potential consequences to the pathology. CONCLUSIONWe identify ChA not only as one of the molecules involved in the etiology of irreversible lysosome dysfunction culminating with lipidosis but also as a promoter of exocytosis of the dysfunctional lysosomes. The latter event is a new mechanism that may be important in the pathogenesis of atherosclerosis.

cell biology↗

bioRxiv2020

Histone demethylome map reveals combinatorial gene regulatory functions in embryonic stem cells

Epigenetic regulators and transcription factors establish distinct regulatory networks for gene regulation to maintain the embryonic stem cell (ESC) state. Although much has been learned regarding individual epigenetic regulators, their combinatorial functions remain elusive. Here, we report previously unknown combinatorial functions of histone demethylases (HDMs) in gene regulation of mouse ESCs. Generation of a histone demethylome (HDMome) map of 20 well-characterized HDMs based on their genome-wide binding revealed co-occupancy of HDMs in different combinations: KDM1A-KDM4B-KDM6A and JARID2-KDM2B-KDM4A-KDM4C-KDM5B largely co-occupy at enhancers and promoters, respectively. Mechanistic studies uncover that KDM1A-KDM6A combinatorially modulates P300/H3K27ac, H3K4me2 deposition and OCT4 recruitment that directs the OCT4/CORE regulatory network for target gene expression; while co-operative actions of JARID2-KDM2B-KDM4A-KDM4C-KDM5B control H2AK119ub1 and bivalent marks of polycomb-repressive complexes that facilitate the PRC regulatory network for target gene repression. Thus, combinatorial functions of HDMs differentially impact gene expression programs in mESCs.

genomics↗