Biology subjects

Bui, H.

Publications and source records attributed to Bui, H..

9 recordsLinked to original sources

bioRxiv2025

White and Brown Adipose Tissue Share a Common Fibro-Adipogenic Progenitor Population

Adipose tissue heterogeneity has emerged as a central factor in regulating adipose tissue function in physiology and pathophysiology, yet tools to model and study this diversity in vitro remain limited. Here, we performed single-cell RNA sequencing on cultured primary white and brown preadipocytes to assess how in vitro conditions impact progenitor identity. We identified two major subpopulations in both depots: committed adipogenic precursors (CAPs) and fibro-adipogenic progenitor-like cells (FAPLs). Remarkably, FAPLs were also present in brown adipose tissue, expanding the known landscape of progenitor populations in this depot. Trajectory and regulon analyses revealed that both white and brown FAPLs exhibit similar pro-fibrotic, stress-responsive signatures and diverge early from proliferating progenitor states. Integration of datasets showed that FAPLs from both depots cluster together, emphasizing their conserved identity, while CAPs remain depot-specific. Comparison to previously published in vivo single-cell datasets revealed that these in vitro populations, including brown adipose FAPLs, correspond to adipose-resident progenitor subtypes, validating the physiological relevance of this model for studying adipose tissue heterogeneity and development.

physiology↗

bioRxiv2025

Comparative spatial transcriptomics of hair follicle-T cell interactions in mouse, dog and human reveals conserved drivers of primary cicatricial alopecia

Primary cicatricial alopecias (PCA) encompass several autoimmune disorders characterized by scarring hair loss. Many of these conditions are lymphocytic and are thought to be driven by T cell populations. Here, we sought to characterize potential T cell-hair follicle communication pathways in the microanatomical niche using spatial transcriptomics across 3 mammalian species including a novel mouse model, spontaneous disease in companion dogs and human archival diagnostic biopsies. Flow cytometry of mouse model skin confirmed loss of CD34+ bulge cells and keratinocytes, and bulk microarray and histology revealed expression of collagens and development of fibrosis. In vivo ear imaging in mice engrafted with Kikume photoconvertible OT1 CD8+ T cells confirmed long-lived RFP+ T cells in skin arrest near hair follicles and recruit other GFP+ T cells. OT1 T cells expressed CD69, CD103, CD122 and CD62L, which is a binding partner of CD34. Digital spatial profiling using CD3, CD8 and CD45 cell masking identified CXCR3 ligands and IFN response genes in hair follicles, and "metabolic" pathways in T cells, which were also recapitulated in dog and human biopsies. Bulk human RNA as well as spatial analysis of perifollicular T cells confirmed enrichment of CD69 and SELL/CD62L. Different pathways predominated in other CD3+ regions of interest in CD4+ driven conditions including mucocutaneous lupus erythematosus and subacute cutaneous lupus erythematosus. Last, we identify novel drug-targetable pathways, namely CFD and S100A8/9, that could be further explored to disrupt processes in these conditions through veterinary and human trials.

immunology↗

bioRxiv2024

Inheritance of old mitochondria controls early CD8+ T cell fate commitment and is regulated by autophagy

T cell immunity is impaired during ageing, particularly in memory responses needed for efficient vaccination. Autophagy and asymmetric cell division (ACD) are cell biological mechanisms key to memory formation, which undergo a decline upon ageing. However, despite the fundamental importance of these processes in cellular function, the link between ACD and in vivo fate decisions has remained highly correlative in T cells and in the field of mammalian ACD overall. Here we provide robust causal evidence linking ACD to in vivo T cell fate decisions and our data are consistent with the concept that initiation of asymmetric T cell fates is regulated by autophagy. Analysing the proteome of first-daughter CD8+ T cells following TCR-triggered activation, we reveal that mitochondrial proteins rely on autophagy for their asymmetric inheritance and that damaged mitochondria are polarized upon first division. These results led us to evaluate whether mitochondria were asymmetrically inherited and to functionally address their impact on T cell fate. For this we used a novel mouse model that allows sequential tagging of mitochondria in mother and daughter cells, enabling their isolation and subsequent in vivo analysis of CD8+ T cell progenies based on pre-mitotic cell cargo. Autophagy-deficient CD8+ T cells showed impaired clearance and symmetric inheritance of old mitochondria, suggesting that degradation events promote asymmetry and are needed to generate T cells devoid of old organelles. Daughter cells inheriting old mitochondria are more glycolytic and upon adoptive transfer show reduced memory potential, whereas daughter cells that have not inherited old mitochondria from the mother cell are long-lived and expand upon cognate-antigen challenge. Proteomic and single-cell transcriptomic analysis of cells inheriting aged mitochondria suggest that their early fate divergence relies on one carbon metabolism as a consequence of poor mitochondrial quality and function. These findings increase our understanding of how T cell diversity is early-imprinted during division and will help foster the development of strategies to modulate T cell function. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/577412v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@526135org.highwire.dtl.DTLVardef@6c04b1org.highwire.dtl.DTLVardef@1a834fforg.highwire.dtl.DTLVardef@2f70f8_HPS_FORMAT_FIGEXP M_FIG The MitoSnap model allows tracking of pre-mitotic and post-mitotic cell cargoes. Both segregation and degradation (autophagy) contribute to the asymmetric inheritance of old mitochondria. Old mitochondria impact cell metabolism and function. Cells devoid of old mitochondria exhibit better memory potential in vivo. C_FIG

cell biology↗

bioRxiv2023

Heme biosynthesis regulates BCAA catabolism and thermogenesis in brown adipose tissue

With age, people tend to accumulate body fat and reduce energy expenditure1. Brown (BAT) and beige adipose tissue dissipate heat and increase energy expenditure via the activity of the uncoupling protein UCP1 and other thermogenic futile cycles2,3. The activity of brown and beige depots inversely correlates with BMI and age4-11, suggesting that promoting thermogenesis may be an effective approach for combating age-related metabolic disease12-15. Heme is an enzyme cofactor and signaling molecule that we recently showed to regulate BAT function16. Here, we show that heme biosynthesis is the primary contributor to intracellular heme levels in brown adipocytes. Inhibition of heme biosynthesis leads to mitochondrial dysfunction and reduction in UCP1. Although supplementing heme can restore mitochondrial function in heme-synthesis-deficient cells, the downregulation of UCP1 persists due to the accumulation of the heme precursors, particularly propionyl-CoA, which is a product of branched-chain amino acids (BCAA) catabolism. Cold exposure promotes BCAA uptake in BAT, and defects in BCAA catabolism in this tissue hinder thermogenesis17. However, BCAAs contribution to the TCA cycle in BAT and WAT never exceeds 2% of total TCA flux18. Our work offers a way to integrate current literature by describing heme biosynthesis as an important metabolic sink for BCAAs.

cell biology↗

bioRxiv2023

Chemoproteomic Profiling Reveals that Anti-Cancer Natural Product Dankastatin B Covalently Targets Mitochondrial VDAC3

Chlorinated gymnastatin and dankastatin alkaloids derived from the fungal strain Gymnascella dankaliensis have been reported to possess significant anti-cancer activity but their mode of action is unknown. These members possess electrophilic functional groups that may undergo covalent bond formation with specific proteins to exert their biological activity. To better understand the mechanism of action of this class of natural products, we mapped the proteome-wide cysteine-reactivity of the most potent of these alkaloids, dankastatin B, using activitybased protein profiling chemoproteomic approaches. We identified a primary target of dankastatin B in breast cancer cells as cysteine C65 of the voltage-dependent anion selective channel on the outer mitochondrial membrane VDAC3. We demonstrated direct and covalent interaction of dankastatin B with VDAC3. VDAC3 knockdown conferred hyper-sensitivity to dankastatin B-mediated anti-proliferative effects in breast cancer cells indicating that VDAC3 was at least partially involved in the anti-cancer effects of this natural product. Our study reveals a potential mode of action of dankastatin B through covalent targeting of VDAC3 and highlight the utility of chemoproteomic approaches in gaining mechanistic understanding of electrophilic natural products.

biochemistry↗

bioRxiv2021

Maize inbred line B96 is the source of large-effect loci for resistance to generalist but not specialist spider mites

Maize (Zea mays subsp. mays) yield loss from arthropod herbivory is substantial. While the basis of resistance to major insect herbivores has been comparatively well-studied in maize, less is known about resistance to spider mite herbivores, which are distantly related to insects and feed by a different mechanism. Two spider mites, the generalist Tetranychus urticae, and the grass-specialist Oligonychus pratensis, are notable pests of maize, especially during drought conditions. We assessed the resistance to both mite species of 38 highly diverse maize lines, including several previously reported to be resistant to one or the other mite species. We found that line B96, as well as its derivatives B49 and B75, were highly resistant to T. urticae. In contrast, neither these three lines, nor any others included in our study, were notably resistant to O. pratensis. Quantitative trait locus (QTL) mapping with F2 populations from crosses of B49, B75, and B96 to susceptible B73 identified a large-effect QTL on chromosome 6 as underlying T. urticae resistance in each line, with an additional QTL on chromosome 1 in B96. Genome sequencing and haplotype analyses identified B96 as the apparent sole source of resistance haplotypes. Our study identifies loci for use in maize breeding programs for T. urticae resistance, as well as to assess if the molecular-genetic basis of spider mite resistance is shared with insect pests of maize, as B96 is also among the most resistant known maize lines to several insects, including the European corn borer, Ostrinia nubilalis. Key message Maize(Zea mays subsp. mays) inbred lines B49, B75, and B96 harbor large-effect loci for resistance to the generalist spider mite Tetranychus urticae, but not the specialist Oligonychus pratensis.

genetics↗

bioRxiv2020

Thyroid hormone regulates proximodistal identity in the fin skeleton

Across the [~]30,000 species of ray-finned fish, fins show incredible diversity in overall shape and in the patterning of the supportive bony rays. Fin length mutant zebrafish have provided critical insights into the developmental pathways that regulate relative fin size. However, the processes that govern skeletal patterning along the proximodistal axis of the fin have remained less well understood. Here, we show that thyroid hormone regulates proximodistal identity of fin rays, distalizing gene expression profiles, morphogenetic processes during outgrowth, and ultimate morphology of the fin. This role for thyroid hormone in specifying proximodistal identity appears conserved between development and regeneration, in all the fins, and between species. We demonstrate that proximodistal identity is regulated independently from pathways that determine size, and we show that modulating proximodistal patterning relative to growth can recapitulate the spectrum of fin ray diversity found in nature.

developmental biology↗

bioRxiv2019

Loss of acid sphingomyelinase ameliorates disease progression in a vertebrate model of Glucocerebrosidase deficiency

The additive effect of genetic risk variants on overall disease risk is a plausible but frequently unproven hypothesis. To test this hypothesis, we assessed the biological effect of combined glucocerebrosidase (GCase) and acid sphingomyelinase (ASM) deficiency. Variants in both glucocerebrosidase1 (GBA1) and sphingomyelinase (SMPD1) are genetic risk factors for Parkinsons disease. Unexpectedly, ASM deficiency resulted in normalized behaviour and prolonged survival in gba1-/-;smpd1-/- double-mutant zebrafish compared to gba1-/-. RNAseq-based pathway analysis confirmed a profound rescue of neuronal function and intracellular homeostasis. We identified complete reciprocal rescue of mitochondrial respiratory chain function and abolished lipid membrane oxidation in gba1-/-;smpd1-/- compared to gba1-/- or smpd1-/- as the underlying rescue mechanism. Complementing in vitro experiments demonstrated an unexpected reduction of -synuclein levels in human cell lines with combined GCase and ASM deficiency. Our study highlights the importance of functional validation for any putative interactions between genetic risk factors and their overall effect on disease-relevant mechanisms rather than readily assuming an additive effect. SummaryThe additive effect of genetic risk variants on disease risk is a popular but typically unproven hypothesis. We investigated this hypothesis mechanistically for Parkinsons disease risk factors and provide evidence of an unexpected rescue effect on neuronal function and survival.

genetics↗

bioRxiv2018

Long-term population studies uncover the genome structure and genetic basis of xenobiotic and host plant adaptation in the herbivore Tetranychus urticae

Pesticide resistance arises rapidly in arthropod herbivores, as can host plant adaptation, and both are significant problems in agriculture. These traits have been challenging to study as both are often polygenic and many arthropods are genetically intractable. Here, we examined the genetic architecture of pesticide resistance and host plant adaptation in the two-spotted spider mite, Tetranychus urticae, a global agricultural pest. We show that the short generation time and high fecundity of T. urticae can be readily exploited in experimental evolution designs for high-resolution mapping of quantitative traits. As revealed by selection with spirodiclofen, an acetyl-CoA decarboxylase inhibitor, in populations from a cross between a spirodiclofen resistant and a susceptible strain, and which also differed in performance on tomato, we found that a limited number of loci could explain quantitative resistance to this compound. These were resolved to narrow genomic intervals, suggesting specific candidate genes, including acetyl-CoA decarboxylase itself, clustered and copy variable cytochrome P450 genes, and NADPH cytochrome P450 reductase, which encodes a redox partner for cytochrome P450s. For performance on tomato, candidate genomic regions for response to selection were distinct from those responding to the synthetic compound and were consistent with a more polygenic architecture. In accomplishing this work, we exploited the continuous nature of allele frequency changes across experimental populations to resolve the existing fragmented T.urticae draft genome to pseudochromosomes. This improved assembly was indispensable for our analyses, as it will be for future research with this model herbivore that is exceptionally amenable to genetic studies.

genetics↗