Biology subjects

Johnson, B. J.

Publications and source records attributed to Johnson, B. J..

9 recordsLinked to original sources

bioRxiv2025

Ivermectin Reduces Withdrawal-Induced Alcohol Intake via CeA GABAergic Enhancement

Although FDA-approved medications for alcohol use disorder (AUD) are available, their efficacy varies across patients, highlighting the need for novel therapeutics that address inter-individual differences in disease etiology and treatment response. Genetic models, particularly heterogeneous stock (HS) rats, recapitulate human-like genetic diversity and behavioral heterogeneity, enabling the dissection of individual differences in vulnerability to AUD and pharmacotherapeutic sensitivity. P2X4 receptors, which are encoded by the gene P2rx4, are ATP-gated ion channels inhibited by ethanol and abundantly expressed in neurons found in reward and stress circuits. P2X4 receptors have emerged as key modulators of ethanol sensitivity and consumption in preclinical models. Here, we genetically predicted P2rx4 expression in whole brain in a cohort of 130 HS rats exposed to chronic intermittent ethanol (CIE) vapor and phenotyped for self-administration during acute abstinence. Rats were dichotomized into high- and low-predicted expression groups. Higher predicted P2rx4 expression was associated with increased post-vapor intake and escalation. In 32 CIE-escalated rats, ivermectin, a positive allosteric modulator of P2X4 receptors, dose-dependently reduced drinking. We stratified rats into three groups: non-responders, mild responders, and high responders. Electrophysiological recordings from CeA slices revealed that ivermectin differentially enhanced GABAergic IPSCs: high-responders exhibited sustained increases in IPSC frequency and selective amplitude reductions, while the two other groups showed transient frequency increases. All groups displayed prolonged rise times, however non-responders showed extended decay times. These findings suggest that P2rx4 upregulation serves as a vulnerability marker for dependence-like behaviors, with ivermectin attenuating withdrawal-driven alcohol consumption by enhancing CeA GABAergic inhibition.

pharmacology and toxicology↗

bioRxiv2024

Revealing unseen dynamical regimes of ecosystems from population time-series data

Many ecosystems can exist in alternative dynamical regimes for which small changes in an environmental driver can cause sudden jumps between regimes. However, predicting the dynamics of regimes that occur under unobserved levels of the environmental driver has remained an unsolved challenge in ecology with important implications for conservation and management. Here we show that integrating population time-series data and information on the putative driver into an empirical dynamic model allows us to predict new dynamical regimes without the need to specify a population dynamics model. As a proof of concept, we demonstrate that we can accurately predict fixed-point, cyclic, or chaotic dynamics under unseen driver levels for a range of simulated models. For a model with an abrupt population collapse, we show that our approach can anticipate the regime that follows the tipping point. We then apply our approach to data from an experimental microbial ecosystem and from a lake planktonic ecosystem. We find that we can reconstruct transitions away from chaos in the experimental ecosystem and anticipate the dynamics of the oligotrophic regime in the lake ecosystem. These results lay the groundwork for making rational decisions about preventing, or preparing for, regime shifts in natural ecosystems.

ecology↗

bioRxiv2022

High Sox2 expression predicts taste lineage competency of lingual progenitors in vitro.

SO_SCPLOWUMMARYC_SCPLOWTaste buds on the tongue are collections of taste receptor cells (TRCs) that detect sweet, sour, salty, umami and bitter stimuli. Like non-taste lingual epithelium, TRCs are renewed from basal keratinocytes, many of which express the transcription factor SOX2. Genetic lineage tracing has shown SOX2+ lingual progenitors give rise to both taste and non-taste lingual epithelium in the posterior circumvallate taste papilla (CVP) of mice. However, SOX2 is variably expressed among CVP cells suggesting that their progenitor potential may vary. Using transcriptome analysis and organoid technology, we show highly expressing SOX2+ cells are taste-competent progenitors that give rise to organoids comprising both TRCs and lingual epithelium, while organoids derived from low-expressing SOX2+ progenitors are composed entirely of non-taste cells. Hedgehog and WNT/{beta}-catenin are required for taste homeostasis in adult mice, but only WNT/{beta}-catenin promotes TRC differentiation in vitro and does so only in organoids derived from higher SOX2+ taste lineage-competent progenitors.

developmental biology↗

bioRxiv2021

A new method for improving extraction efficiency and purity of urine and plasma cell-free DNA

This study assessed three commercially available cell-free DNA (cfDNA) extraction kits and the impact of a PEG-based DNA cleanup procedure (DNApure) on cfDNA quality and yield. Six normal donor urine and plasma samples, and specimens from four pregnant (PG) women carrying male fetuses underwent extractions with the JBS cfDNA extraction kit (kit J), MagMAX Cell-Free DNA Extraction kit (kit M), and QIAamp Circulating Nucleic Acid Kit (kit Q). Recovery of a PCR product spike-in, endogenous TP53, and Y-chromosome DNA was used to assess kit performance. Nucleosomal-sized DNA profiles varied among the kits, with prominent multi-nucleosomal-sized peaks present in urine and plasma DNA isolated by kits J and M only. Kit J recovered significantly more spike-in DNA compared with kit M or Q (p<0.001) from urine, and similar amounts from plasma (p=0.12). Applying DNApure to kit M- and Q-isolated DNA significantly improved the amplification efficiency of spike-in DNA from urine (p<0.001) and plasma (p[≤]0.013). Furthermore, kit J isolated significantly more Y-chromosome DNA from PG urine compared to kit Q (p=0.05). We conclude that DNApure provides an efficient means of improving the yield and purity of cfDNA and minimizing effects of pre-analytical biospecimen variability on liquid biopsy assay performance.

molecular biology↗

bioRxiv2020

Mark-release-recapture of male Aedes aegypti (Diptera: Culicidae): use of rhodamine B to estimate movement, mating and population parameters in preparation for an incompatible male program.

Rapid advances in biological and digital technologies are revolutionizing the population control of invasive disease vectors such as Aedes aegypti. Methods such as the sterile and incompatible insect techniques (SIT/IIT) rely on modified males to seek out and successfully mate with females, and in doing so outcompete the wild male population for mates. Currently, these interventions infer the success of mating interactions between male and female insects through area-wide population surveillance and observations of mating competitiveness are rare. Furthermore, little is known about male Ae. aegypti behaviours and biology in field settings. In preparation for a large, community scale IIT program, we undertook a series of mark-release-recapture experiments using rhodamine B to mark male Ae. aegypti sperm and measure mating interactions with females. We also developed the Spatial and Temporally Evolving Isotropic Kernel (STEIK) framework to assist researchers to estimate the movement of individuals through space and time. Results showed that ~40% of daily females captured were unmated, suggesting interventions will need to release males regularly to be effective at suppressing Ae. aegypti populations. Males moved rapidly through the landscape, particularly when released during the night. Although males moved further than what is typically observed in females of the species, survival was considerably lower. These unique insights will lead to a greater understanding of mating interactions in wild insect populations and lay the foundation for robust suppression strategies in the future. Author SummaryModern scientific techniques for controlling populations of the dengue vector, Aedes aegypti, utilize the mating biology of adult male mosquitoes to achieve suppression through a sterilization process. As the study of Ae. aegypti control has typically focused on adult female mosquitoes, knowledge on male movement, survival and mating interactions in the field is lacking. Here we undertook several mark-release-recapture experiments on adult male Ae. aegypti in Innisfail, Australia, and measured important biological parameters. For the first time in large field experiments, we employed rhodamine B as a marker that when fed to adult males, identified both marked males and the wild females they mated with. We observed males moving further through the landscape, but surviving for a shorter period, than previous measurements undertaken on females in a field setting. A high proportion (~40%) of unmated females suggests individuals are constantly available for mating. As such, sterile male strategies may need to release at regular intervals to achieve effective population suppression. The unique insights provided by this study will assist in designing future sterile male field interventions.

ecology↗

bioRxiv2020

Modelling the Wolbachia Incompatible Insect Technique: strategies for effective mosquito population elimination

The Wolbachia Incompatible Insect Technique (IIT) shows promise as a method for eliminating invasive mosquitoes such as Aedes aegypti (Linnaeus)(Diptera: Culicidae) and reducing the incidence of vector-borne diseases such as dengue, chikungunya and Zika. Successful implementation of this biological control strategy relies on high-fidelity separation of male from female insects in mass production systems for inundative release into landscapes. Processes for sex-separating mosquitoes are typically error prone, laborious and IIT programs run the risk of releasing Wolbachia infected females and replacing wild mosquito populations. We introduce a simple Markov Population Process (MPP) model for studying mosquito populations subjected to a Wolbachia-IIT program which exhibit an unstable equilibrium threshold. The model is used to study, in silico, scenarios that are likely to yield a successful elimination result. Our results suggest that elimination is best achieved by releasing males at rates that adapt to the ever-decreasing wild population, thus reducing the risk of releasing Wolbachia-infected females while reducing costs. While very high-fidelity sex-separation is required to avoid establishment, release programs tend to be robust to the release of a small number of Wolbachia-infected females. These findings will inform and enhance the next generation of Wolbachia-IIT control strategies that are already showing great promise in field trials.

zoology↗

bioRxiv2020

Performance of aerial Bacillus thuringiensis var. israelensis applications in mixed saltmarsh-mangrove systems and use of affordable unmanned aerial systems to identify problematic levels of canopy cover

BACKGROUNDIn the Australian southeast, the saltmarsh mosquito Aedes vigilax (Skuse) is the focus of area-wide larviciding campaigns employing the biological agent Bacillus thuringiensis var. israelensis (Bti). Although generally effective, frequent inundating tides and considerable mangrove cover can make control challenging. Here, we describe the efficacy and persistence of an aqueous Bti suspension (potency: 1200 International Toxic Units; strain AM65-52) within a mixed saltmarsh-mangrove system and the use of affordable unmanned aerial systems (UAS) to identify and map problematic levels of mangrove canopy cover. RESULTSHigh mangrove canopy density (>40% cover) reduced product deposition by 74.5% (0.013{+/-} 0.002 l/cm2 vs. 0.051{+/-} 0.006 l/cm2), larval mortality by 27.7% (60.7{+/-} 4.1% vs. 84.0{+/-} 2.4%), and ground level Bti concentrations by 32.03% (1144 {+/-} 462.6 vs. 1683 {+/-} 447.8 spores ml-1) relative to open saltmarsh. Persistence of product post-application was found to be low (80.6% loss at 6 h) resulting in negligible additional losses to tidal inundation 24 h post-application. UAS surveys accurately identified areas of high mangrove cover using both standard and multispectral imagery, although derived index values for this vegetation class were only moderately correlated with ground measurements (R2=0.17-0.38) at their most informative scales. CONCLUSIONThese findings highlight the complex operational challenges that affect coastal mosquito control in heterogeneous environments. The problem is exacerbated by continued mangrove transgression into saltmarsh habitat in the region. Emerging UAS technology can help operators optimize treatments by accurately identifying and mapping challenging canopy cover using both standard and multispectral imaging.

microbiology↗

bioRxiv2020

What happens on islands, doesn't stay on islands: Patterns of synchronicity in mosquito nuisance and host-seeking activity between a mangrove island and adjacent coastal development

Coastal development is expanding globally in response to mass human migration, yet urban planning guidelines often overlook the problems that human encroachment on or near coastal mosquito habitat may cause. This study aimed at elucidating the frequency and magnitude of dispersal of highly vagile saltmarsh mosquitoes from productive off-shore bay islands to adjacent coastal human developments. Inter-population dynamics and daily host-seeking activity of saltmarsh mosquitoes were monitored daily at 15-minute intervals within a productive bay island and adjacent coastal development in southeast Queensland, Australia, using emerging smart trap technology over a 2-month period of high mosquito activity. The regulation of mosquito dispersal and host-seeking activity by local environmental factors, e.g. temperature, relative humidity and hourly wind patterns, were also investigated. The data show that the primary saltmarsh mosquitoes Aedes vigilax (Skuse) and Culex sitiens (Wiedemann) disperse from offshore breeding sites to neighboring mainland areas in high numbers and in highly synchronized waves despite unfavorable wind patterns and the need to traverse a considerable expanse (ca. 1.4 km) of open water. Patterns of host-seeking activity within each site were also remarkably similar despite notable differences in the local environment demonstrating a consistency in host-seeking activity across disparate habitats. These findings demonstrate that distant saltmarsh habitats, including offshore breeding sites, are likely to be primary sources of mosquito nuisance for coastal housing developments. This observation highlights the need to develop new planning and regulatory guidelines that alert urban planners to the risks of encroaching on habitats close to the sources of highly vagile mosquito species.

ecology↗

bioRxiv2018

In vivo measurements reveal a single 5’ intron is sufficient to increase protein expression level in C. elegans

Introns can increase gene expression levels using a variety of mechanisms collectively referred to as Intron Mediated Enhancement (IME). To date, the magnitude of IME has been quantified in human cell culture and plant models by comparing intronless reporter gene expression levels to those of intron-bearing reporter genes in vitro (mRNA, Western Blots, protein activity), using genome editing technologies that lacked full control of locus and copy number. Here, for the first time, we quantified IME in vivo, in terms of protein expression levels, using fluorescent reporter proteins expressed from a single, defined locus in Caenorhabditis elegans. To quantify the magnitude of IME, we developed a microfluidic chip-based workflow to mount and image individual animals, including software for operation and image processing. We used this workflow to systematically test the effects of position, number and sequence of introns on two different proteins, mCherry and mEGFP, driven by two different promoters, vit-2 and hsp-90. We found the three canonical synthetic introns commonly used in C. elegans transgenes increased mCherry protein concentration by approximately 50%. The naturally-occurring introns found in hsp-90 also increased mCherry expression level by about 50%. Furthermore, and consistent with prior results examining mRNA levels, protein activity or phenotypic rescue, we found that a single, natural or synthetic, 5 intron was sufficient for the full IME effect while a 3 intron was not. IME was also affected by protein coding sequence (50% for mCherry and 80% for mEGFP) but not strongly affected by promoter 46% for hsp-90 and 54% for the stronger vit-2. Our results show that IME of protein expression in C. elegans is affected by intron position and contextual coding sequence surrounding the introns, but not greatly by promoter strength. Our combined controlled transgenesis and microfluidic screening approach should facilitate screens for factors affecting IME and other intron-dependent processes.

genetics↗