Biology subjects

Cheah, M.

Publications and source records attributed to Cheah, M..

4 recordsLinked to original sources

bioRxiv2024

Functional maturation and experience-dependent plasticity in adult-born olfactory bulb dopaminergic neurons

Continued integration of new neurons persists in only a few areas of the adult mouse brain. In the olfactory bulb (OB), immature adult-born neurons respond differently to olfactory stimuli compared to their more mature counterparts, and have heightened levels of activity-dependent plasticity. These distinct functional features are thought to bestow unique properties onto existing circuitry. OB interneurons, including those generated through adult neurogenesis, consist of a set of highly distinct subtypes. However, we do not currently know the different cell-type-specific mechanisms underlying their functional development and plastic potential. Here, we specifically characterised electrophysiological maturation and experience-dependent plasticity in a single, defined subtype of adult-born OB neuron: dopaminergic cells. We selectively live-labelled both adult-born and resident dopaminergic cells, and targeted them for whole-cell patch-clamp recordings in acute mouse OB slices. Surprisingly, we found that from the time - at [~]1 month of cell age - that live adult-born dopaminergic neurons could first be reliably identified, they already possessed almost fully mature intrinsic firing properties. We saw significant maturation only in increased spontaneous activity and decreased medium afterhyperpolarisation amplitude. Nor were adult-born dopaminergic cells especially plastic. In response to brief sensory deprivation via unilateral naris occlusion we observed no maturation-specific plastic alterations in intrinsic properties, although we did see deprivation-associated increases in spike speed and amplitude across all adult-born and resident neurons. Our results not only show that adult-born OB dopaminergic cells rapidly functionally resemble their pre-existing counterparts, but also underscore the importance of subtype identity when describing neuronal maturation and plasticity.

neuroscience↗

bioRxiv2024

Strikingly different neurotransmitter release strategies in dopaminergic subclasses

Neuronal function is intimately tied to axodendritic polarity. Neurotransmitter release, for example, is usually the role of the axon. There are widespread exceptions to this rule, however, including many mammalian neuronal types that can release neurotransmitter from their dendrites. In the mouse olfactory bulb, closely related subclasses of dopaminergic interneuron differ markedly in their polarity, with one subtype lacking an axon entirely. These axon-bearing and anaxonic dopaminergic subclasses have distinct developmental profiles and sensory responses, but how their fundamental polarity differences translate to functional outputs remains entirely unknown. Here, we provide anatomical evidence for distinct neurotransmitter release strategies among these closely related dopaminergic subtypes: anaxonic cells release from their dendrites, while axon-bearing neurons release exclusively from their intermittently myelinated axon. These structural differences are linked to a clear functional distinction: anaxonic, but not axon-bearing dopaminergic neurons are capable of self-inhibition. Our findings suggest that variations in polarity can produce striking distinctions in neuronal outputs, and that even closely related neuronal subclasses may play entirely separate roles in sensory information processing.

neuroscience↗

bioRxiv2023

A semiconductor 96-microplate platform for real-time impedance-based high-throughput screening

Profiling compounds and genetic perturbations via high-content imaging has become increasingly popular for drug discovery, but the technique is limited to endpoint images of fixed cells. In contrast, electronic-based devices offer label-free, functional information of live cells, yet current approaches suffer from low-spatial resolution or single-well throughput. Here, we report a semiconductor 96-microplate platform designed for high-resolution real-time impedance "imaging" at scale. Each well features 4,096 electrodes at 25 {micro}m spatial resolution while a miniaturized data interface allows 8x parallel plate operation (768 total wells) within each incubator for enhanced throughputs. New electric field-based, multi-frequency measurement techniques capture >20 parameter images including tissue barrier, cell-surface attachment, cell flatness, and motility every 15 min throughout experiments. Using these real-time readouts, we characterized 16 cell types, ranging from primary epithelial to suspension, and quantified heterogeneity in mixed epithelial and mesenchymal co-cultures. A proof-of-concept screen of 904 diverse compounds using 13 semiconductor microplates demonstrates the platforms capability for mechanism of action (MOA) profiling with 25 distinct responses identified. The scalability of the semiconductor platform combined with the translatability of the high dimensional live-cell functional parameters expands high-throughput MOA profiling and phenotypic drug discovery applications.

bioengineering↗

bioRxiv2021

Integrin-driven Axon Regeneration in the Spinal Cord Activates a Distinctive CNS Regeneration Program

The peripheral branch of sensory dorsal root ganglion (DRG) neurons regenerates readily after injury unlike their central branch in the spinal cord. However extensive regeneration and reconnection of sensory axons in the spinal cord can be driven by the expression of 9 integrin and its activator kindlin- 1(9k1), which enable axons to interact with tenascin-C. To elucidate the mechanisms and downstream pathways affected by activated integrin expression and central regeneration, we conducted transcriptomic analyses of DRG sensory neurons transduced with 9k1, and controls, with and without axotomy of the central branch. Expression of 9k1 without the central axotomy led to upregulation of a known PNS regeneration program, including many genes associated with peripheral nerve regeneration. Coupling 9k1 treatment with dorsal root axotomy led to extensive central axonal regeneration and caused expression of a distinctive CNS regeneration program, including genes associated with ubiquitination, autophagy, endoplasmic reticulum, trafficking, and signalling. Pharmacological inhibition of these processes blocked the regeneration of axons from DRGs and human iPS-derived sensory neurons, validating their causal contributions. This CNS regeneration- associated program showed little correlation with either embryonic development or PNS regeneration programs. Potential transcriptional drivers of this CNS program coupled to regeneration include Mef2a, Runx3, E2f4, Tfeb, Yy1. Signalling from integrins primes sensory neurons for regeneration, but their axon growth in the CNS is associated with a distinctive program that differs from that involved in PNS regeneration.

neuroscience↗