Biology subjects

Bui, B. V.

Publications and source records attributed to Bui, B. V..

11 recordsLinked to original sources

bioRxiv2026

Optimisation of OptoDrum protocol for measuring optomotor response in juvenile & adult zebrafish

Zebrafish (Danio rerio) are an important vertebrate model for vision and neuroscience research. In the larval stages, the aquatic species begins to elicit the optomotor response (OMR) to stabilize themselves in water -- a behaviour that may be exploited in the laboratory to measure visual acuity. However, up to now, the measurement of the OMR in juvenile and adult zebrafish has been limited due to their behavioural complexity. Here, we optimize a protocol to assay zebrafish aged between 4 and 9 weeks-post-fertilization, by displaying sinusoidal gratings parallel to the zebrafish eye to elicit a robust OMR. We assessed the visual spatial-frequency tuning function of an environmentally induced myopia model to confirm the sensitivity and robustness of the protocol. Additionally, we show the OMR is sensitive to the contrast and temporal resolution of the sinusoidal gratings. Furthermore, we found that the time between stimulus presentations impact the spatial-frequency tuning function likely as time is required for zebrafish to return to baseline swimming after eliciting the OMR. Finally, we found that the OMR after ten versus twenty seconds of stimulus onset appears comparable; indicating that robust OMR responses in zebrafish can be elicited through relatively short stimulus presentations. Through the experiments conducted, we present an optimized protocol specific to zebrafish. The protocol may be used to follow the progression or treatment efficacy of progressive neurological disorders including specific visual disorders and higher brain functions with visual endophenotypes. Ultimately, this protocol allows for high-throughput robust measures of visual and neural function in zebrafish.

neuroscience↗

bioRxiv2024

Characterisation of RNA editing and gene therapy with a compact CRISPR-Cas13 in the retina

CRISPR-Cas13 nucleases are programmable RNA-targeting effectors that can silence gene expression in a reversible manner. Recent iterations of Cas13 nucleases are compact for adeno-associated virus (AAV) delivery to achieve strong and persistent expression in various organs in a safe manner. Here, we report significant transcriptomic signatures of Cas13bt3 expression in retinal cells and show all-in-one AAV gene therapy with Cas13bt3 can effectively silence VEGFA mRNA in human retinal organoids and humanised VEGF transgenic mouse (trVEGF029, Kimba) models. Specifically, human embryonic stem cells (hESC)-derived retinal pigment epithelium cells show high expression of Cas13bt3 from virus delivery corresponding to a significant reduction of VEGFA mRNA. We further show that intravitreal delivery of Cas13bt3 can transduce mouse retinal cells efficiently, reaching the photoreceptors for specific knockdown of human VEGFA in the Kimba mouse. Our results reveal important considerations for assessing Cas13 activity and establish Cas13bt3 as a potential anti-VEGF agent that can achieve long-term control of VEGFA for the treatment of retinal neovascularization.

molecular biology↗

bioRxiv2024

A precision medicine approach for HCN1 Developmental and Epileptic Encephalopathy

Pathogenic variants in HCN1 causing cation leak result in a severe developmental and epileptic encephalopathy (DEE). Current treatment options for patients with HCN1-DEE are limited and are insufficient to fully address both the seizures and clinical comorbidities of this disorder. Org 34167 is a brain penetrant broad-spectrum HCN channel inhibitor that has completed phase I clinical trials. We used a range of assays at molecular, cellular, network and behavioural levels to explore the potential of Org 34167 as a precision medicine for HCN1-DEE. Org 34167 restored the voltage sensitivity of the DEE HCN1M305L mutated channel, significantly reducing cation leak. It also restored Ih-mediated sag, hyperpolarised the resting membrane potential and reduced firing of layer V neurons from the Hcn1M294L mouse model of HCN1-DEE, which was engineered based on the HCN1M305L pathogenic variant. Additionally, Org 34167 reduced neuronal epileptiform activity and restored retinal light sensitivity in these mice, suggesting it may improve both seizures and other clinical comorbidities. However, Org 34167-mediated tremors were noted at therapeutic doses. Org 34167 was also effective at reducing cation leak caused by five additional HCN1 pathogenic variants, suggesting broader utility. Overall, these data demonstrate that a small molecule HCN inhibitor can restore channel and consequent physiological functions, positioning it as a promising precision therapeutic approach for HCN1-DEE.

neuroscience↗

bioRxiv2023

EFEMP1 contributes to light-dependent ocular growth in zebrafish

Myopia (short-sightedness) is the most common ocular disorder. It generally develops after over-exposure to aberrant visual environments, disrupting emmetropization mechanisms that should match eye growth with optical power. A pre-screening of strongly associated myopia-risk genes identified through human genome-wide association studies implicates efemp1 in myopia development, but how this gene impacts ocular growth remains unclear. Here, we modify efemp1 expression specifically in the retina of zebrafish. We found that under normal lighting, efemp1 mutants developed axial myopia, enlarged eyes, reduced spatial vision and altered retinal function. However, under myopia-inducing dark-rearing, compared to control fish, mutants remained emmetropic and showed changes in retinal function. Efemp1 modification changed the expression of efemp1, egr1, tgfb1a, vegfab and rbp3 genes in the eye, and changes the inner retinal distributions of myopia-associated EFEMP1, TIMP2 and MMP2 proteins. Efemp1 modification also impacted dark-rearing-induced responses of vegfab and wnt2b genes and above-mentioned myopia-associated proteins. Together, we provided robust evidence that light-dependent ocular growth is regulated by efemp1. SummaryThis study shows that retina-specific modification of efemp1 expression in zebrafish results in myopic eye, and impacts responses to myopia-inducing dark-rearing in eye growth, retinal function, and myopia-associated molecular expression and distribution, implicating light-dependent regulation of efemp1 in ocular development.

neuroscience↗

bioRxiv2023

Establishment and comprehensive characterization of a novel dark-reared zebrafish model for myopia studies

PurposeMyopia is predicted to impact approximately 5 billion people by 2050, necessitating mechanistic understanding of its development. Myopia results from dysregulated genetic mechanisms of emmetropization, caused by over-exposure to aberrant visual environments; however, these genetic mechanisms remain unclear. Recent human genome-wide association studies have identified a range of novel myopia-risk genes. To facilitate large-scale in vivo mechanistic examination of gene-environment interactions, this study aims to establish a myopia model platform that allows efficient environmental and genetic manipulations. MethodsWe established an environmental zebrafish myopia model by dark-rearing. Ocular biometrics including relative ocular refraction were quantified using optical coherence tomography images. Spatial vision was assessed using optomotor response (OMR). Retinal function was analyzed via electroretinography (ERG). Myopia-associated molecular contents or distributions were examined using RT-qPCR or immunohistochemistry. ResultsOur model produces robust phenotypic changes, showing myopia after 2 weeks of dark-rearing, which were recoverable within 2 weeks after returning animals to normal lighting. 2-week dark-reared zebrafish have reduced spatial-frequency tuning function. ERG showed reduced photoreceptor and bipolar cell function (a- and b-waves) after only 2 days of dark-rearing, which worsened after 2 weeks of dark-rearing. We also found dark-rearing-induced changes to expression of myopia-risk genes, including egr1, vegfaa, vegfab, rbp3, gjd2a and gjd2b, inner retinal distribution of EFEMP1, TIMP2 and MMP2, as well as transiently reduced PSD95 density in the inner plexiform layer. ConclusionsCoupled with the gene editing tools available for zebrafish, our environmental myopia model provides an excellent platform for large-scale investigation of gene-environment interactions in myopia development.

neuroscience↗

bioRxiv2021

TAK1: a potential therapeutic target for retinal neovascularization

Retinal neovascularization, or pathological angiogenesis in the retina, is a leading cause of blindness in developed countries. Transforming growth factor-{beta}-activated kinase 1 (TAK1) is a mitogen-activated protein kinase kinase kinase (MAPKKK) activated by TGF-{beta}1 and other pro-inflammatory cytokines. TAK1 is also a key mediator of inflammation, innate immune responses, apoptosis and tissue homeostasis and plays an important role in physiological angiogenesis. Its role in pathological angiogenesis, particularly in retinal neovascularization, remains unclear. We investigated the regulatory role of TAK1 in pathological angiogenesis in the retina. Transcriptome analysis of human retina featuring retinal neovascularization revealed enrichment of known TAK1-mediated signaling pathways. Selective inhibition of TAK1 activation by 5Z-7-oxozeaenol attenuated aberrant retinal angiogenesis in rats following oxygen-induced retinopathy. Transcriptome profiling revealed that TAK1 activation in human microvascular endothelial cells under TNF stimulation led to increase the gene expression related to cytokines and leukocyte-endothelial interaction, mainly through nuclear factor kappa B (NF{kappa}B) signaling pathways. These results reveal that inhibition of TAK1 signaling may have therapeutic value for the treatment of pathological angiogenesis in the retina.

biochemistry↗

bioRxiv2020

Altered visual function in a larval zebrafish knockout of neurodevelopmental risk gene pdzk1

The human PDZK1 gene is located in a genomic susceptibility region for neurodevelopmental disorders. A genome-wide association study (GWAS) identified links between PDZK1 polymorphisms and altered visual contrast sensitivity, an endophenotype for schizophrenia and autism spectrum disorder. The PDZK1 protein is implicated in neurological functioning, interacting with synaptic molecules including post-synaptic density 95 (PSD-95), N-methyl-D-aspartate receptors (NMDAR), corticotropin-releasing factor receptor 1 (CRFR1) and serotonin 2A receptors. To elucidate the role of PDZK1, we generated pdzk1-knockout (pdzk1-KO) zebrafish using CRISPR/Cas-9 genome editing. Visual function of 7-day-old fish was assessed at behavioural and functional levels using the optomotor response (OMR) and scotopic electroretinogram (ERG). We also quantified retinal morphology and densities of PSD-95, NMDAR1, CRFR1 and serotonin in the synaptic inner plexiform layer at 7 days, 4 weeks and 8 weeks of age. Relative to wild-type, pdzk1-KO larvae showed spatial-frequency tuning functions with increased amplitude (likely due to abnormal gain control) and reduced ERG b-waves (suggestive of inner retinal dysfunction). However, these functional differences were not associated with gross synaptic or morphological retinal phenotypes. The findings corroborate a role for pdzk1 in visual function, and our model system provides a platform for investigating other genes associated with abnormal visual behaviour.

neuroscience↗

bioRxiv2020

Fractalkine-induced microglial vasoregulation occurs within the retina and is altered early in diabetic retinopathy

Local blood flow control within the CNS is critical to proper function and is dependent on coordination between neurons, glia and blood vessels. Macroglia such as astrocytes and Muller cells, contribute to this neurovascular unit within the brain and retina, respectively. This study explored the role of microglia, the innate immune cell of the CNS, in retinal vasoregulation and highlights changes during early diabetes. Structurally, microglia were found to contact retinal capillaries and neuronal synapses. In the brain and retinal explants, the addition of fractalkine, the sole ligand for monocyte receptor Cx3cr1, resulted in capillary constriction at regions of microglial contact. This vascular regulation was dependent on microglial involvement, since mice lacking Cx3cr1, exhibited no fractalkine-induced constriction. Analysis of the microglial transcriptome identified several vasoactive genes, including angiotensinogen, a constituent of the renin-angiotensin system (RAS). Subsequent functional analysis showed that RAS blockade via candesartan, abolished microglial-induced capillary constriction. Microglial regulation was explored in a rat streptozotocin (STZ) model of diabetic retinopathy. Retinal blood flow was reduced after 4 weeks due to reduced capillary diameter and this was coincident with increased microglial association. Functional assessment showed loss of microglial-capillary response in STZ-treated animals and transcriptome analysis showed evidence of RAS pathway dysregulation in microglia. While candesartan treatment reversed capillary constriction in STZ-treated animals, blood flow remained decreased likely due to dilation of larger vessels. This work shows microglia actively participate in the neurovascular unit, with aberrant microglial-vascular function possibly contributing to the early vascular compromise during diabetic retinopathy. Significance StatementThis work identifies a novel role for microglia, the innate immune cells of the CNS, in the local control of the retinal vasculature and identifies deficits early in diabetes. Microglia contact neurons and vasculature and express several vasoactive agents. Activation of microglial fractalkine-Cx3cr1 signalling leads to capillary constriction and blocking the renin-angiotensin system (RAS) with candesartan abolishes microglial-mediated vasoconstriction in the retina. In early diabetes, reduced retinal blood flow is coincident with capillary constriction, increased microglial-vessel association, loss of microglial-capillary regulation and altered microglial expression of the RAS pathway. While candesartan restores retinal capillary diameter early in diabetes, targeting of microglial-vascular regulation is required to prevent coincident dilation of large retinal vessels and reduced retinal blood flow.

cell biology↗

bioRxiv2019

Progressive impairments in executive function in the APP/PS1 model of Alzheimer’s disease as measured by translatable touchscreen testing

Executive function deficits in Alzheimers disease (AD) occur early in disease progression and may be predictive of cognitive decline. However, no preclinical studies have identified deficits in rewarded executive function in the commonly used APP/PS1 mouse model. To address this, we assessed 12-26 month old APP/PS1 mice on rewarded reversal and/or extinction tasks. 16-month-old, but not 13- or 26-month-old, APP/PS1 mice showed an attenuated rate of extinction. Reversal deficits were seen in 22-month-old, but not 13-month-old APP/PS1 animals. We then confirmed that impairments in reversal were unrelated to previously reported visual impairments in both AD mouse models and humans. Age, but not genotype, had a significant effect on markers of retinal health, indicating the deficits seen in APP/PS1 mice were directly related to cognition. This is the first characterisation of rewarded executive function in APP/PS1 mice, and has great potential to facilitate translation from preclinical models to the clinic.

animal behavior and cognition↗

bioRxiv2019

MicroRNA-143 plays a protective role in ischemia-induced retinal neovascularization

Retinal neovascularization is a severe complication of proliferative diabetic retinopathy. MicroRNAs (miRNAs) are master regulators of gene expression that play important roles in retinal neovascularization. Here, we investigated the retinal miRNA expression profile in a rat model of oxygen-induced retinopathy (OIR) through miRNA-Seq. We found that miR-143-3p, miR-126-3p, miR-150-5p and miR-145-5p were significantly down-regulated in the retina of OIR rats, and directly involved in the development of retinal neovascularization. Of these identified miRNAs, miR-143 is enriched in retina and was first reported being associated with pathological retinal angiogenesis. Our RNA-Seq data further suggested that miR-143 alleviates retinal neovascularization by mediating the inflammation/stress pathways via Fos. Moreover, the computational analysis indicated that Transforming Growth Factor-beta Activated Kinase 1 (TAK1) is involved in several key pathways associated with the dysregulated miRNAs. The pharmacological inhibition of TAK1 suppressed angiogenesis in vitro and retinal neovascularization in vivo. Our data highlight the utility of next-generation sequencing in the development of therapeutics for ocular neovascularization and further suggest that therapeutic targeting the dysregulated miRNAs or TAK1 may be a feasible adjunct therapeutic approach in patients with retinal neovascularization.

molecular biology↗

bioRxiv2018

Efficacy and dynamics of self-targeting CRISPR/Cas constructs for gene editing in the retina.

Safe delivery of CRISPR/Cas endonucleases remains one of the major barriers to the widespread application of in vivo genome editing including the anticipatory treatment of monogenic retinal diseases. We previously reported the utility of adeno-associated virus (AAV)-mediated CRISPR/Cas genome editing in the retina; however, with this type of viral delivery system, active endonucleases will remain in the retina for an extended period, making genotoxicity a significant consideration in clinical applications. To address this issue, we have designed a self-destructing \"kamikaze\" CRISPR/Cas system that disrupts the Cas enzyme itself following expression. Four guide RNAs (sgRNAs) were designed to target Streptococcus pyogenes Cas9 (SpCas9), after in situ validation, the selected sgRNAs were cloned into a dual AAV vector. One construct was used to deliver SpCas9 and the other delivered sgRNAs directed against SpCas9 and the target locus (yellow fluorescent protein, YFP), in the presence of mCherry. Both constructs were packaged into AAV2 vector and intravitreally administered in C57BL/6 and Thy1-YFP transgenic mice. After 8 weeks the expression of SpCas9, the efficacy of YFP gene disruption was quantified. A reduction of SpCas9 mRNA was found in retinas treated with AAV2-mediated-YFP/SpCas9 targeting CRISPR/Cas compared to those treated with YFP targeting CRISPR/Cas alone. We also show that AAV2-mediated delivery of YFP/SpCas9 targeting CRISPR/Cas significantly reduced the number of YFP fluorescent cells among mCherry-expressing cells (~85.5% reduction compared to LacZ/SpCas9 targeting CRISPR/Cas) in transfected retina of Thy1-YFP transgenic mice. In conclusion, our data suggest that a self-destructive \"kamikaze\" CRISPR/Cas system can be used as a robust tool for refined genome editing in the retina, without compromising on-target efficiency.

genetics↗