Biology subjects

Poon, K.

Publications and source records attributed to Poon, K..

5 recordsLinked to original sources

bioRxiv2026

A novel reaction-diffusion architecture for engineering self-organized patterns in mammalian cells

Reaction-diffusion circuits generate self-organized spatial patterns through local activation and long-range inhibition, but synthetic implementations in mammalian cells have been limited by the differential-diffusion requirement. Here, we introduce a novel architecture, juxtacrine activation with paracrine inhibition (JAPI), where the activator propagates through cell-cell contacts rather than diffusion. We demonstrate mathematically and numerically that JAPI accesses the same patterning regimes as classical diffusion-based circuits with one fewer free parameter. We then engineer compact synNotch-based JAPI circuits in mammalian fibroblasts and demonstrate their sufficiency for self-organized patterning through tunable, size-limited signal propagation. Functionalized to spatially control morphogen secretion, these circuits perturb feather bud formation on adjacent embryonic chicken epidermis. Finally, we develop a library-based approach to explore coupled, dual-JAPI circuits with tunable cross-inhibition, enabling programmable interactions between patterns and access to a broad morphospace of spatial states. Together, JAPI provides a compact, modular platform for programming self-organized multicellular patterning. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=97 SRC="FIGDIR/small/727552v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@fae8c9org.highwire.dtl.DTLVardef@c8eddborg.highwire.dtl.DTLVardef@177d08corg.highwire.dtl.DTLVardef@11cc952_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2025

Derivation of cardiomyocyte-propelled motile aggregates from stem cells

Robotics draws inspiration from biology, particularly animal locomotion based on muscle-driven contractions. While traditional engineering assembles components sequentially, locomotive animals are built via self-organized developmental programs. Stem cells, under the right conditions, can mimic these processes in vitro, offering a pathway to develop muscle-propelled biobots in a self-organized building process. Here, we demonstrate that existent cardiogenic gastruloid protocols can produce motile aggregates from mouse embryonic stem cells, although with very limited efficiency. We then identify a novel protocol that yields contractile aggregates with higher frequency and larger contractile areas. In this novel protocol, mesendoderm induction using TGF-beta ligands is followed by cardiogenic induction with FGFs and VEGF. Synthetic organizers further control contraction localization. Aggregates developed via this protocol show enhanced motility, marking a step forward towards building motile cardiobots from self-organized biological material. This strategy opens new possibilities for designing autonomous biobots and studying the evolution of muscle-powered movement of multicellular organisms and cardiovascular development.

synthetic biology↗

bioRxiv2022

Inhibition of early-acting autophagy genes in C. elegans neurons improves protein homeostasis, promotes exopher production, and extends lifespan via the ATG-16.2 WD40 domain

While autophagy is key to maintain cellular homeostasis, tissue-specific roles of individual autophagy genes are less understood. To study neuronal autophagy in vivo, we inhibited autophagy genes specifically in C. elegans neurons, and unexpectedly found that knockdown of early-acting autophagy genes, i.e., involved in formation of the autophagosome, except for atg-16.2, decreased PolyQ aggregates and increased lifespan, albeit independently of the degradation of autophagosomal cargo. Neuronal aggregates can be secreted from neurons via vesicles called exophers, and we found that neuronal inhibition of early-acting autophagy genes atg-7 and lgg-1/Atg8, but not atg-16.2 increased exopher formation. Moreover, atg-16.2 mutants were unable to form exophers, and atg-16.2 was required for the effects of early autophagy gene reduction on neuronal PolyQ aggregation, exopher formation, and lifespan. Notably, neuronal expression of full-length ATG-16.2 but not ATG-16.2 without a functional WD40 domain, important for non-canonical functions of ATG16L1 in mammalian cells, restored these phenotypes. Collectively, we discovered a specific role for C. elegans ATG-16.2 and its WD40 domain in exopher biogenesis, neuronal proteostasis, and lifespan determination, highlighting a possible role for non-canonical autophagy functions in both exopher formation and in aging.

cell biology↗

bioRxiv2021

Concentration-dependent change in hypothalamic neuronal transcriptome by the dietary fatty acids: oleic and palmitic acids

Prenatal high-fat diet exposure increases hypothalamic neurogenesis events in embryos and programs offspring to be obesity-prone. The molecular mechanism involved in these dietary effects of neurogenesis are unknown. This study investigated the effects of oleic and palmitic acids, which are abundant in a high-fat diet, on the hypothalamic neuronal transcriptome and how these changes impact neurogenesis events. The results show differential effects of low and high concentrations of oleic or palmitic acid treatment on differential gene transcription. Gene ontology analysis uncovered significant gene enrichment in several cellular pathways involved in gene regulation and protein production, particularly with proliferation, migration, and cell survival. The enriched signaling pathways include Wnt, integrin, PDGF, and apoptosis, in addition endocrine function signaling pathways CCKR and GnRH. Further examination of proliferation and migration show low concentrations of oleic acid to stimulate proliferation and high concentrations of both oleic and palmitic acid to stimulate apoptosis. Oleic acid also reduced hypothalamic neuronal migration, with little effects by palmitic acid. The results show direct impact of the two most abundant fatty acids in a high fat diet to directly impact hypothalamic neuronal proliferation and migration. The results also uncovered signaling pathways affected by oleic and palmitic acid and suggest a mechanism of prenatal high-fat diet induced neurogenesis events is through these two abundant fatty acids.

neuroscience↗

bioRxiv2018

Pseudomonas aeruginosa displays a dormancy phenotype during long-term survival in water.

Pseudomonas aeruginosa is capable of long-term survival in water, which may serve as a reservoir for infection. Although viable cell counts of PAO1 incubated in water remain stable throughout 8 weeks, LIVE/DEAD(R) staining indicated a high proportion of cells stained with propidium iodide (PI). The proportion of PI-stained cells increased by 4 weeks, then decreased again by 8 weeks, suggesting an adaptive response. This was also evident in an observed shift in cell morphology from a rod to a coccoid shape after 8 weeks. Fluorescence-activated cell sorting (FACS) was used to recover PI-stained cells, which were plated and shown to be viable, indicating that PI-stained cells were membrane-compromised but still cultivable. PAO1 mid-log cells in water were labeled with the dsDNA-binding dye PicoGreen(R) to monitor viability as well as DNA integrity, which demonstrated that the population remains viable and transitions towards increased dsDNA staining. Metabolic activity was found to decrease significantly in water by 4 weeks. The PAO1 outer membrane became less permeable and more resistant to polymyxin B damage in water, and the profile of total membrane lipids changed over time. None of the individual mutants within a library of ~2500 mapped, mini-Tn5-lux transposon mutants were found to have decreased survival in water. Among the ~1400 transcriptional lux fusions, gene expression in water revealed that the majority of genes were repressed, but subsets of genes were induced at particular time points. In summary, these results indicate that P. aeruginosa is dormant in water and this adaptation involves a complex pattern of gene regulation and changes to the cell to promote long-term survival and antibiotic tolerance. The approach of P. aeruginosa incubated in water may be useful to study antibiotic tolerance and the mechanisms of dormancy and survival in nutrient limiting conditions.

microbiology↗