Biology subjects

Chong, B.

Publications and source records attributed to Chong, B..

5 recordsLinked to original sources

bioRxiv2024

Neuropeptide-dependent spike time precision and plasticity in circadian output neurons

Circadian rhythms influence various physiological and behavioral processes such as sleep-wake cycles, hormone secretion, and metabolism. In Drosophila, an important set of circadian output neurons are called pars intercerebralis (PI) neurons, which receive input from specific clock neurons called DN1. These DN1 neurons can further be subdivided into functionally and anatomically distinctive anterior (DN1a) and posterior (DN1p) clusters. The neuropeptide diuretic hormones 31 (Dh31) and 44 (Dh44) are the insect neuropeptides known to activate PI neurons to control activity rhythms. However, the neurophysiological basis of how Dh31 and Dh44 affect circadian clock neural coding mechanisms underlying sleep in Drosophila is not well understood. Here, we identify Dh31/Dh44-dependent spike time precision and plasticity in PI neurons. We first find that a mixture of Dh31 and Dh44 enhanced the firing of PI neurons, compared to the application of Dh31 alone and Dh44 alone. We next find that the application of synthesized Dh31 and Dh44 affects membrane potential dynamics of PI neurons in the precise timing of the neuronal firing through their synergistic interaction, possibly mediated by calcium-activated potassium channel conductance. Further, we characterize that Dh31/Dh44 enhances postsynaptic potentials in PI neurons. Together, these results suggest multiplexed neuropeptide-dependent spike time precision and plasticity as circadian clock neural coding mechanisms underlying sleep in Drosophila.

neuroscience↗

bioRxiv2024

Neuromechanical Phase Lags and Gait Adaptation in the Nematode C. elegans

Undulation is a locomotor strategy in which waves of bending propagate along the body.This form of locomotion is observed in organisms that span orders of magnitude in size and represent diverse habitats and species. Despite this diversity, common neuromechanical phenomena have been observed across biologically disparate undulators, due to common mechanics. For example, Neuromechanical Phase Lags (NPL), a phenomenon where waves of muscle contraction travel at different speeds than body bends, have been observed in fish, lamprey and lizards. Existing theoretical descriptions of this phenomenon implicate the role of physical body-environment interactions. However, systematic experimental variation of body-environment interactions and measurement of the corresponding phase lags has not been performed. Using the nematode Caenorhabditis elegans we measured muscle and body curvature dynamics simultaneously, performing calcium imaging in the body wall muscles while systematically varying the environmental rheology. A mechanical model demonstrates that the measured phase lags are controlled by the relative strength of elastic torques within the body and resistive forces within the medium. We further show that the phase lags correspond with a difference in the wavenumber of the muscle activity and curvature patterns. Hence, the environmental forces that create NPL also act as a filter that shapes and modulates the gait commanded by the nervous system. Beyond nematodes, the simplicity of our model further suggests that tuning body elasticity may serve as a general means of modulating the degree of mechanical control in other undulators.

biophysics↗

bioRxiv2024

Antithrombotic Efficacy and Bleeding Risks of Vaccine-Induced Immune Thrombotic Thrombocytopenia Treatments

Current guidelines for treating vaccine-induced immune thrombotic thrombocytopenia (VITT) recommend non-heparin anticoagulants and intravenous immunoglobulin (IVIg). However, the efficacy of these treatments remains uncertain due to a lack of comparative clinical trials or animal studies. A recent study proposed danaparoid and heparin as potential VITT therapies due to their ability to disrupt VITT IgG-PF4 binding. Here, we examined the effects of various anticoagulants (including unfractionated (UF) heparin, danaparoid, bivalirudin, fondaparinux, and argatroban), IVIg, and the Fc{gamma}RIIa receptor-blocking antibody, IV.3, in relation to VITT pathophysiology. Our investigation focused on VITT IgG-PF4 binding, platelet activation, thrombocytopenia, and thrombosis. Danaparoid, at therapeutic doses, was the sole anticoagulant that reduced VITT IgG-PF4 binding, verified by purified anti-PF4 specific VITT IgG. Low-dose UF heparin (< 2U/mL) augmented VITT IgG binding to PF4 on platelets. While danaparoid and high-dose UF heparin (10 U/mL) inhibited platelet activation, none of the anticoagulants significantly affected thrombocytopenia in our VITT animal model, and all prolonged bleeding time. IVIg and all anticoagulants, except UF heparin, protected VITT mice from thrombosis. Direct Fc{gamma}RIIa receptor inhibition with IV.3 antibody proved the most effective approach for managing both thrombosis and thrombocytopenia in VITT. Our results underscore the necessity of animal model investigations to inform patient treatment strategies. This study provides compelling evidence for developing Fc{gamma}RIIa receptor blockers to treat VITT and other Fc{gamma}RIIa-related thrombotic inflammatory disorders. Key pointsO_LINon-heparin anticoagulants and IVIg reduce thrombosis in vivo by varying degrees whereas heparin exacerbates thrombosis. C_LIO_LIDirect blocking of Fc{gamma}RIIa receptor is the most effective strategy to treating both thrombosis and thrombocytopenia in VITT. C_LI

immunology↗

bioRxiv2023

Comprehensive genome editing confers "off-the-shelf" CAR-T cells superior efficacy against solid tumors

Biochemical and immunological negative regulators converge to inhibit tumor-reactive Chimeric Antigen Receptor T (CAR-T) cells, which may explain clinical failures of CAR-T cell therapies against solid tumors. Here, we developed a multifaceted approach to genetically engineer allogeneic ( off -the-shelf) CAR-T cells resistant to both biochemical (adenosine) and immunological (PD-L1 and TGF-{beta}) inhibitory signaling. We multiplexed an adenine base editor with a CRISPR-Cas12b nuclease to manufacture a CAR-T cell product comprising six gene edits to evade allorejection (B2M, CIITA), prevent graft-versus-host disease (CD3E) and resist major biochemical (ADORA2A) and immunological (PDCD1, TGFBR2) immunosuppressive barriers in solid tumors. Combinatorial genetic disruption in CAR-T cells enabled superior anti-tumor efficacy leading to improved tumor elimination and survival in humanized mouse models that recapitulated the suppressive features of a human tumor microenvironment (TME). This novel engineering strategy conferred CAR-T cells resistance to a diverse TME, which may unlock the therapeutic potential of CAR-T cells against solid tumors. One Sentence SummaryMultiplex genome engineered CAR-T cells resistant to allorejection and the convergence of biochemical and immunological negative regulators within the tumor microenvironment exhibit superior efficacy against solid tumors.

cell biology↗

bioRxiv2022

Active and passive mechanics for rough terrain traversal in centipedes

Centipedes coordinate body and limb flexion to generate propulsion. On flat solid surfaces, the limb-stepping patterns can be characterized according to the direction in which limbaggregates propagate, opposite to (retrograde) or with the direction of motion (direct). It is unknown how limb and body dynamics are modified in terrain with terradynamic complexity more representative of their natural heterogeneous environments. Here, we investigated how centipedes that use retrograde and direct limp-stepping patterns, S. polymorpha and S. sexspinosus, respectively, coordinate their body and limbs to navigate laboratory environments which present footstep challenges and terrain rugosity. We recorded the kinematics and measured the locomotive performance of these animals traversing two rough terrains with randomly distributed step heights and compared the kinematics to those on a flat frictional surface. S. polymorpha exhibited similar body and limb dynamics across all terrains and a decrease in speed with increased terrain roughness. Unexpectedly, when placed in a rough terrain, S. sexspinosus changed the limb-stepping pattern from direct to retrograde. Further, for both species, traversal of rough terrains was facilitated by hypothesized passive mechanics: upon horizontal collision of a limb with a block, the limb passively bent and later continued the stepping pattern. While centipedes have many degrees of freedom. our results suggest these animals negotiate limb-substrate interactions and navigate complex terrains, by offloading complex control and leveraging the innate flexibility of their limbs.

animal behavior and cognition↗