Biology subjects

Ngo, N.

Publications and source records attributed to Ngo, N..

6 recordsLinked to original sources

bioRxiv2026

The Infant Brainstem - A Multimodal Multiscale Postmortem Imaging Pipeline

Brainstem disorders in human infants - including sudden infant death syndrome (SIDS), the leading cause of postnatal infant mortality in the United States - are characterized by cellular and molecular abnormalities that conventional neuroimaging cannot detect. A substantial challenge arises from the fact that the immature myelination of the infant brain severely degrades MRI contrast, leaving the discrete nuclei and white matter tracts of the brainstem poorly resolved at the scale where pathology occurs. We introduce a postmortem imaging pipeline that bridges this gap by integrating four spatially registered modalities: whole-brain magnetic resonance imaging (MRI) (550 m), brainstem-specific MRI (150 m), polarization-sensitive optical coherence tomography (PSOCT, 10 m), and histology with immunohistochemistry (1.88 m). Our central finding is that PSOCT provides excellent tissue contrast independent of myelination state - directly overcoming the principal limitation of MRI in the infant brain -while enabling three-dimensional visualization of nuclei and tracts at resolutions 15 to 55 times finer than MRI alone. Histology provides cellular-level ground truth and validates the optical contrasts. Applied here to a normative 34-day-old infant brainstem, this pipeline establishes a generalizable framework for studying infant brainstem neuroanatomy in three dimensions, with particular relevance to disorders such as SIDS where gross anatomy is intact but cellular abnormalities remain the target of investigation.

neuroscience↗

bioRxiv2025

In vivo validation of the palmitoylation cycle as a therapeutic target in NRAS-mutant cancer

Ras proteins are functionally dependent on one or more lipid modifications.1,2 The dynamic palmitoylation of N-Ras by DHHC palmitoyl acyltransferases and depalmitoylation by ABHD17 serine hydrolases is essential for the growth of NRAS-mutant acute myeloid leukemia (AML) cells.3-6 Here we show that ABD778, an in vivo-active ABHD17 inhibitor, selectively reduces the growth of NRAS-mutant AML and melanoma cell lines and is synergistic with the MEK inhibitor PD0325901 (PD901; mirdametinib). Mechanistically, ABD778 and PD901 induce deep and durable suppression of mitogen activated protein kinase (MAPK) pathway activation. Co-treatment extended the survival of mice transplanted with NrasG12D AMLs, which acquired by-pass mutations at relapse that conferred drug resistance and restored MAPK activation. ABD778 augmented the anti-leukemia activity of PI3 kinase, pan-Ras tri-complex, and FLT3 inhibitors, and restored gilteritinib sensitivity in a patient-derived xenograft model of FLT3 inhibitor resistance. These studies validate the palmitoylation cycle as a therapeutic target in NRAS-mutant cancers.

cancer biology↗

bioRxiv2023

Inflammation causes insulin resistance via interferon regulatory factor 3 (IRF3)-mediated reduction in FAHFA levels

Obesity-induced inflammation causes metabolic dysfunction, but the mechanisms remain elusive. Here we show that the innate immune transcription factor interferon regulatory factor (IRF3) adversely affects glucose homeostasis through induction of the endogenous FAHFA hydrolase androgen induced gene 1 (AIG1) in adipocytes. Adipocyte-specific knockout of IRF3 protects mice against high-fat diet-induced insulin resistance, whereas overexpression of IRF3 or AIG1 in adipocytes promotes insulin resistance on a high-fat diet. Furthermore, pharmacological inhibition of AIG1 reversed obesity-induced insulin resistance and restored glucose homeostasis in the setting of adipocyte IRF3 overexpression. We, therefore, identify the adipocyte IRF3/AIG1 axis as a crucial link between obesity-induced inflammation and insulin resistance and suggest an approach for limiting the metabolic dysfunction accompanying obesity.

physiology↗

bioRxiv2022

Chemoproteomic identification of a dipeptidyl peptidase 4 (DPP4) homolog in Bacteroides thetaiotaomicron important for envelope integrity and fitness

Serine hydrolases play important roles in signaling and human metabolism, yet little is known about the functions of these enzymes in gut commensal bacteria. Using bioinformatics and chemoproteomics, we identify serine hydrolases in the gut commensal Bacteroides thetaiotaomicron that are specific to the Bacteroidetes phylum. Two are predicted homologs of the human protease dipeptidyl peptidase 4 (hDPP4), a key enzyme that regulates insulin signaling. Functional studies reveal that BT4193 is a true homolog of hDPP4 while the other is misannotated and is a proline-specific triaminopeptidase. We demonstrate that BT4193 is important for envelope integrity and is inhibited by FDA-approved type 2 diabetes drugs that target hDPP4. Loss of BT4193 reduces B. thetaiotaomicron fitness during in vitro growth within a diverse community. Taken together, our findings suggest that serine hydrolases contribute to gut microbiota dynamics and may be off-targets for existing drugs that could cause unintended impact on the microbiota.

microbiology↗

bioRxiv2020

ABHD17 enzymes regulate dynamic plasma membrane palmitoylation and N-Ras-dependent cancer growth

A subset of Ras proteins, including N-Ras, depend on a palmitoylation/depalmitoylation cycle to regulate their subcellular trafficking and oncogenicity. General lipase inhibitors such as Palmostatin M block N-Ras depalmitoylation, but lack specificity and target several enzymes displaying depalmitoylase activity. Here, we describe ABD957, a potent and selective covalent inhibitor of the ABHD17 family of depalmitoylases, and show that this compound impairs N-Ras depalmitoylation in human acute myeloid leukemia (AML) cells. ABD957 produced partial effects on N-Ras palmitoylation compared to Palmostatin M, but was much more selective across the proteome, reflecting a plasma membrane-delineated action on dynamically palmitoylated proteins. Finally, ABD957 impaired N-Ras signaling and the growth of NRAS-mutant AML cells in a manner that synergizes with MEK inhibition. Our findings uncover a surprisingly restricted role for ABHD17 enzymes in modulating the N-Ras palmitoylation cycle and suggest that ABHD17 inhibitors may have value as targeted therapies for NRAS-mutant cancers.

cancer biology↗

bioRxiv2019

Single-cell profiling and SCOPE-seq reveal the lineage dynamics of adult neurogenesis and NOTUM as a key V-SVZ regulator

Neural stem cells (NSCs) and their progeny reside in specialized niches in the adult mammalian brain where they generate new neurons and glia throughout life. Adult NSCs of the ventricular-subventricular zone (V-SVZ) are prone to rapid exhaustion; thus timely, context-dependent neurogenesis demands adaptive signaling among the vast number of neighboring progenitors nestled between the ventricular surface and nearby blood vessels. To dissect adult neuronal lineage progression and regulation, we profiled >56,000 V-SVZ and olfactory bulb (OB) cells by single-cell RNA-sequencing (scRNA-seq). Our analyses revealed the diversity of V-SVZ-derived OB neurons, the temporal dynamics of lineage progression, and a key intermediate NSC population enriched for expression of Notum, which encodes a secreted WNT antagonist. Single Cell Optical Phenotyping and Expression (SCOPE-seq), a technology linking live cell imaging with scRNA-seq, uncovered dynamic control of cell size concomitant with NSC differentiation with Notum+ NSCs at a critical size poised for cell division, and a preference of NOTUM surface binding to neuronal precursors with active WNT signaling. Finally, in vivo pharmacological inhibition of NOTUM significantly expanded neuronal precursor pools in the V-SVZ. Our findings highlight a critical regulatory state during NSC activation marked by NOTUM, a secreted enzyme that ensures efficient neurogenesis by preventing WNT signaling activation in NSC progeny.

neuroscience↗