Biology subjects

Lin, A. J.

Publications and source records attributed to Lin, A. J..

5 recordsLinked to original sources

bioRxiv2025

Light-Controlled Synthetic Communication Networks via Paired Connexon Nanopores

Living cells employ dynamic networks for intercellular communication and cooperation, leading to tissue-wide activity. One emerging challenge in the field of bottom-up synthetic biology is emulating such sophisticated behaviors in liposome-based synthetic cells (SCs). Fabricating communication networks in lipid bilayer-based SCs remains a challenge as signaling molecules must transit through two consecutive membranes to transfer information between different SCs. Here, we address this obstacle by engineering connexin channels that directly connect the lumens of adhering SC membranes. We focus on orthogonal channel-forming connexins, namely connexin 43 and connexin 32, and re-design their channel activity to be UV- and near IR-responsive, respectively. By combining engineered connexins into a single SC assembly, we demonstrate orthogonal transfer of reactive signaling molecules between SCs, giving rise to unique reaction products and network states in a wavelength-dependent manner - an important step toward synthetic communication networks.

synthetic biology↗

bioRxiv2024

Microglia-astrocyte interplay mitigates Aβ toxicity in a novel human 3D neurosphere model of Alzheimer's Disease

BackgroundAlzheimers Disease (AD) is characterized by progressive amyloid beta (A{beta}) deposition in the brain, with eventual widespread neurodegeneration. While the cell-specific molecular signature of end-stage AD is reasonably well characterized through autopsy material, less is known about the molecular pathways in the human brain involved in the earliest exposure to A{beta}. Human model systems that not only replicate the pathological features of AD but also the transcriptional landscape in neurons, astrocytes and microglia are crucial for understanding disease mechanisms and for identifying novel therapeutic targets. MethodsIn this study, we used a human 3D iPSC-derived neurosphere model to explore how resident neurons, microglia and astrocytes and their interplay are modified by chronic amyloidosis induced over 3 to 5 weeks by supplementing media with synthetic A{beta}1-42 oligomers. Neurospheres under chronic A{beta} exposure were grown with or without microglia to investigate the functional roles of microglia. Neuronal activity and oxidative stress were monitored using genetically encoded indicators, including GCaMP6f and roGFP1, respectively. Single nuclei RNA sequencing (snRNA-seq) was performed to profile A{beta} and microglia driven transcriptional changes in neurons and astrocytes, providing a comprehensive analysis of cellular responses. ResultsMicroglia efficiently phagocytosed A{beta} inside neurospheres and significantly reduced neurotoxicity, mitigating amyloidosis-induced oxidative stress and neurodegeneration following different exposure times to A{beta}. The neuroprotective effects conferred by the presence of microglia was associated with unique gene expression profiles in astrocytes and neurons, including several known AD-associated genes such as APOE. These findings reveal how microglia can directly alter the molecular landscape of AD. ConclusionsOur human 3D neurosphere culture system with chronic A{beta} exposure reveals how microglia may be essential for the cellular and transcriptional responses in AD pathogenesis. Microglia are not only neuroprotective in neurospheres but also act as key drivers of A{beta}-dependent APOE expression suggesting critical roles for microglia in regulating APOE in the AD brain. This novel, well characterized, functional in vitro platform offers unique opportunities to study the roles and responses of microglia to A{beta} modelling key aspects of human AD. This tool will help identify new therapeutic targets, accelerating the transition from discovery to clinical applications. HighlightsO_LIWell-characterized functional human iPSC-derived 3D neurospheres (hiNS) consisting of neurons and astrocytes can be supplemented with microglia/macrophages (hiMG) C_LIO_LIChronic amyloidosis in the presence of hiMG recapitulate key features and gene expression profiles of AD C_LIO_LIhiMG within the model phagocytose A{beta} and mitigate A{beta}-induced neurotoxicity, reducing oxidative stress and neuronal damage C_LIO_LIhiMG are essential for A{beta} to upregulate AD-like gene expression signatures in astrocytes C_LIO_LIImmunohistochemical analysis reveals hiMG-dependent colocalization of A{beta} and APOE C_LI

neuroscience↗

bioRxiv2024

A microglia-containing cerebral organoid model to study early life immune challenges

Prenatal infections and activation of the maternal immune system have been proposed to contribute to causing neurodevelopmental disorders (NDDs), chronic conditions often linked to brain abnormalities. Microglia are the resident immune cells of the brain and play a key role in neurodevelopment. Disruption of microglial functions can lead to brain abnormalities and increase the risk of developing NDDs. How the maternal as well as the fetal immune system affect human neurodevelopment and contribute to NDDs remains unclear. An important reason for this knowledge gap is the fact that the impact of exposure to prenatal risk factors has been challenging to study in the human context. Here, we characterized a model of cerebral organoids (CO) with integrated microglia (COiMg). These organoids express typical microglial markers and respond to inflammatory stimuli. The presence of microglia influences cerebral organoid development, including cell density and neural differentiation, and regulates the expression of several ciliated mesenchymal cell markers. Moreover, COiMg and organoids without microglia show similar but also distinct responses to inflammatory stimuli. Additionally, IFN-{gamma} induced significant transcriptional and structural changes in the cerebral organoids, that appear to be regulated by the presence of microglia. Specifically, interferon-gamma (IFN-{gamma}) was found to alter the expression of genes linked to autism. This model provides a valuable tool to study how inflammatory perturbations and microglial presence affect neurodevelopmental processes.

neuroscience↗

bioRxiv2023

Can non-invasive brain stimulation modulate peak alpha frequency in the human brain? A systematic review and meta-analysis

Peak alpha frequency, the dominant oscillatory frequency within the alpha range (8-12 Hz), is associated with cognitive function and several neurological conditions, including chronic pain. Manipulating PAF could offer valuable insight into the relationship between PAF and various functions and conditions and provide new treatment avenues. This systematic review aimed to comprehensively synthesise effects of non-invasive brain stimulation (NIBS) on PAF speed. Relevant studies assessing PAF pre- and post-NIBS in healthy adults were identified through systematic searches of electronic databases (Embase, PubMed, PsychINFO, Scopus, The Cochrane Library) and trial registers. The Cochrane risk-of-bias tool was employed for assessing study quality. Quantitative analysis was conducted through pairwise meta-analysis when possible; otherwise, qualitative synthesis was performed. The review protocol was registered with PROSPERO (CRD42020190512) and the Open Science Framework (https://osf.io/2yaxz/). Eleven NIBS studies were included, all with a low risk-of-bias, comprising seven transcranial alternating current stimulation (tACS), three repetitive transcranial magnetic stimulation (rTMS), and one transcranial direct current stimulation (tDCS) study. Meta-analysis of active tACS conditions (eight conditions from five studies) revealed no significant effects on PAF (mean difference [MD] = -0.12, 95% CI = -0.32 to 0.08, p = 0.24). Qualitative synthesis provided no evidence that tDCS altered PAF and moderate evidence for transient increases in PAF with 10 Hz rTMS. There is limited evidence that NIBS can modulate PAF, and existing evidence does not demonstrate robust effects. Further studies employing standardised stimulation protocols are necessary to determine the potential of NIBS to modulate PAF.

neuroscience↗

bioRxiv2023

Cardiac Troponin I Directly Binds and Inhibits Mitochondrial ATP Synthase: a Noncanonical Role in the Post-Ischemic Heart

Cardiac troponin I (cTnI) is a sarcomeric protein critical to myocyte contraction. Unexpectedly, we found that some cTnI localized to the mitochondrial matrix in the heart, inhibited mitochondrial functions when stably expressed in non-cardiac cells and increased opening of the mitochondrial permeability transition pore under oxidative stress. Direct, specific, and saturable binding of cTnI to ATP synthase was demonstrated in vitro, using immune-captured ATP synthase, and in cells using proximity ligation assay. cTnI binding doubled F1F0 ATPase activity, whereas skeletal troponin I and several human mutant cTnI variants associated with familial hypertrophic cardiomyopathy did not. A rationally-designed ten amino acid peptide, P888, inhibited cTnI binding to ATP synthase, inhibited cTnI-induced increase in ATPase activity in vitro, and reduced cardiac injury following transient ischemia in vivo. We therefore suggest that mitochondria-associated cTnI may inhibit cardiac ATP synthase under basal conditions; pharmacological agents that release this inactivating effect of cTnI and thus preventing ATP hydrolysis during cardiac ischemia may increase the reservoir of functional mitochondria to reduce cardiac injury. Significance StatementCardiac troponin I (cTnI) is a key sarcomeric protein involved in the regulation of myocardial contractility. We found that some cTnI is present in the mitochondrial matrix where it binds to ATP synthase, disrupting mitochondrial function; inhibition of the cTnI-ATP synthase interaction with a selective peptide inhibitor reduces cardiac dysfunction following ischemia and reperfusion injury. Several pathogenic cTnI mutations associated with hypertrophic cardiomyopathy do not affect ATP synthase activity, suggesting a potential mechanism that contributes to the diverse pathologies associated with these mutations.

cell biology↗