Biology subjects

Ng, H. H.

Publications and source records attributed to Ng, H. H..

4 recordsLinked to original sources

bioRxiv2022

miRNA upregulate protein and glycan expression via direct activation in proliferating cells

The dominant paradigm is that miRNA binding to mRNA represses protein expression. Activation by miRNA has been observed in select circumstances (quiescent cells, mitochondria), but is not thought a feature of miRNA action in actively dividing cells. Herein, we comprehensively map the miRNA regulation of -2,6-sialyltransferases ST6GAL1 and ST6GAL2 using a high-throughput assay (miRFluR). We find the majority of miRNA targeting ST6GAL1, the main enzyme controlling -2,6-sialylation, upregulate protein expression. In contrast, those that regulate ST6GAL2 are predominantly downregulatory. We provide evidence that miRNA-mediated upregulation occurs in proliferating cells and is a direct effect. Further, we show that AGO2 and FXR1 are required. Our data expands current understanding of miRNA, providing strong evidence of both upregulatory and downregulatory roles for these non-coding RNA. One-Sentence SummarymiRNA directly activate expression of -2,6-sialyltransferases and sialylation, expanding miRNA actions in dividing cells.

biochemistry↗

bioRxiv2022

Time-dependent Role of Bisphosphonates on Atherosclerotic Plaque Calcification

Atherosclerotic plaque calcification directly contributes to the leading cause of morbidity and mortality by affecting the plaque vulnerability and rupture risk. Small microcalcifications can increase plaque stress and promote rupture, whereas large calcifications can stabilize plaques. Drugs that target bone mineralization may lead to unintended consequences on ectopic plaque calcification and cardiovascular outcomes. Bisphosphonates, common anti-osteoporotic agents, elicited unexpected cardiovascular events in clinical trials. Here, we investigated the role of bisphosphonates treatment and timing on the disruption or promotion of vascular calcification and bone mineral in a mouse model of atherosclerosis. We started the bisphosphonate treatment either before plaque formation, at early plaque formation times associated with the onset of calcification, or at late stages of plaque development. Our data indicate that long term bisphosphonate treatment (beginning prior to plaque development) leads to higher levels of plaque calcification, with a narrower mineral size distribution. When given later in plaque development, we measured a wider distribution of mineral size. These morphological alterations may associate with higher risk of plaque rupture by creating stress foci. Yet, bone mineral density positively correlated with the duration of bisphosphonate treatment.

bioengineering↗

bioRxiv2021

Epidermal Growth Factor Receptor Inhibition Prevents Caveolin-1-dependent Calcifying Extracellular Vesicle Biogenesis

Chronic kidney disease (CKD) increases the risk of cardiovascular disease, including vascular calcification, leading to higher mortality. Release of calcifying extracellular vesicles (EVs) by vascular smooth muscle cells (VSMCs) promotes the ectopic mineralization of vessel walls. Caveolin-1 (CAV1) protein plays a key role in genesis of calcifying EVs in VSMCs. Epidermal growth factor receptor (EGFR) co-localizes with and influences the intracellular trafficking of CAV1. Using a diet-induced mouse model of CKD, we measured serum EGFR and assessed the potential of EGFR inhibition to prevent vascular calcification. Mice with CKD developed widespread vascular calcification, which associated with increased serum levels of EGFR. We computationally analyzed 7651 individuals in the Multi-Ethnic Study of Atherosclerosis (MESA) and Framingham cohorts to assess potential correlations between coronary artery calcium and single nucleotide polymorphisms (SNPs) associated with elevated serum levels of EGFR. Individuals in the MESA and Framingham cohorts with SNPs associated with increased serum EGFR exhibit elevated coronary artery calcium. In both the CKD mice and human VSMC culture, EGFR inhibition significantly reduced vascular calcification by mitigating the release of CAV1-positive calcifying EVs. EGFR inhibition also increased bone mineral density in CKD mice. Given that EGFR inhibitors exhibit clinical safety and efficacy in other pathologies, the current data suggest that EGFR may be an ideal target to prevent pathological vascular calcification.

pathology↗

bioRxiv2017

The role of Cdx2 as a lineage specific transcriptional repressor for pluripotent network during trophectoderm and inner cell mass specification

The first cellular differentiation event in mouse development leads to the formation of the blastocyst consisting of the inner cell mass (ICM) and an outer functional epithelium called trophectoderm (TE). The lineage specific transcription factor CDX2 is required for proper TE specification, where it promotes expression of TE genes, and represses expression of Pou5f1 (OCT4) by inhibiting OCT4 from promoting its own expression. However its downstream network in the developing early embryo is not fully characterized. Here, we performed high-throughput single embryo qPCR analysis in Cdx2 null embryos to identify components of the CDX2-regulated network in vivo. To identify genes likely to be regulated by CDX2 directly, we performed CDX2 ChIP-Seq on trophoblast stem (TS) cells, derived from the TE. In addition, we examined the dynamics of gene expression changes using an inducible CDX2 embryonic stem (ES) cell system, so that we could predict which CDX2-bound genes are activated or repressed by CDX2 binding. By integrating these data with observations of chromatin modifications, we were able to identify novel regulatory elements that are likely to repress gene expression in a lineage-specific manner. Interestingly, we found CDX2 binding sites within regulatory elements of key pluripotent genes such as Pou5f1 and Nanog, pointing to the existence of a novel mechanism by which CDX2 maintains repression of OCT4 in trophoblast. Our study proposes a general mechanism in regulating lineage segregation during mammalian development.

cell biology↗