Biology subjects

Poulsen, R.

Publications and source records attributed to Poulsen, R..

6 recordsLinked to original sources

bioRxiv2026

Microphysiological Flow Batteries For Dynamic EDC Screening Of mESC-derived Thyroid Organoids

Endocrine disrupting chemicals (EDCs) are ubiquitous environmental contaminants capable of dysregulating the production of thyroid hormones. Traditional thyroid toxicological assays rely on 2D cell cultures and animal models, both of which fail to accurately recapitulate human thyroid physiology and provide limited mechanistic insight into EDC toxicity. To overcome these limitations, we report a novel thyroid-on-chip platform integrating mouse embryonic stem cell-derived thyroid organoids with advanced organ-on-chip (OoC) technology and downstream multi-omics analysis. The platform leverages a reversibly-sealed microphysiological flow battery (MFB) to allow scale up of dynamic organoid culture and controlled chemical exposure while reducing operational complexity. Upon EDC exposure, transcriptomic and proteomic analysis revealed new molecular signatures of thyroid disruption across four different EDC classes, even at very low EDC concentrations (1nM), validating the capacity of this system to mechanistically dissect EDC-induced responses. This represents an integrated platform consists of an advanced physiologically relevant assay framework for next-generation endocrine toxicity testing, bridging the gap between in vitro screening and in vivo thyroid physiology.

bioengineering↗

bioRxiv2024

Human Accelerated Regions regulate gene networks implicated in apical-to-basal neural progenitor fate transitions

The evolution of the human cerebral cortex involved modifications in the composition and proliferative potential of the neural stem cell (NSC) niche during brain development. Human Accelerated Regions (HARs) exhibit a significant excess of human-specific sequence changes and have been implicated in human brain evolution. Multiple studies support that HARs include neurodevelopmental enhancers with novel activities in humans, but their biological functions in NSCs have not been empirically assessed at scale. Here we conducted a direct-capture Perturb-seq screen repressing 180 neurodevelopmentally active HARs in human iPSC-derived NSCs with single-cell transcriptional readout. After profiling >188,000 NSCs, we identified a set of HAR perturbations with convergent transcriptional effects on gene networks involved in NSC apicobasal polarity, a cellular process whose precise regulation is critical to the developmental emergence of basal radial glia (bRG), a progenitor population that is expanded in humans. Across multiple HAR perturbations, we found convergent dysregulation of specific apicobasal polarity and adherens junction regulators, including PARD3, ABI2, SETD2, and PCM1. We found that the repression of one candidate from the screen, HAR181, as well as its target gene CADM1, disrupted apical PARD3 localization and NSC rosette formation. Our findings reveal interconnected roles for HARs in NSC biology and cortical development and link specific HARs to processes implicated in human cortical expansion.

neuroscience↗

bioRxiv2024

Evidence for auditory stimulus-specific adaptation but not deviance detection in larval zebrafish brains

Animals receive a constant stream of sensory input, and detecting changes in this sensory landscape is critical to their survival. One signature of change detection in humans is the auditory mismatch negativity (MMN), a neural response to unexpected stimuli that deviate from a predictable sequence. This process requires the auditory system to adapt to specific repeated stimuli while remaining sensitive to novel input (stimulus-specific adaptation). MMN was originally described in humans, and equivalent responses have been found in other mammals and birds, but it is not known to what extent this deviance detection circuitry is evolutionarily conserved. Here we present the first evidence for stimulus-specific adaptation in the brain of a teleost fish, using whole-brain calcium imaging of larval zebrafish at single-neuron resolution with selective plane illumination microscopy. We found frequency-specific responses across the brain with variable response amplitudes for frequencies of the same volume, and created a loudness curve to model this effect. We presented an auditory oddball stimulus in an otherwise predictable train of pure tone stimuli, and did not find a population of neurons with specific responses to deviant tones that were not otherwise explained by stimulus-specific adaptation. Further, we observed no deviance responses to an unexpected omission of a sound in a repetitive sequence of white noise bursts. These findings extend the known scope of auditory adaptation and deviance responses across the evolutionary tree, and lay groundwork for future studies to describe the circuitry underlying auditory adaptation at the level of individual neurons.

neuroscience↗

bioRxiv2022

Relationship between thyroid hormones and associated metabolites and gene expression bioindicators in the serum of Rana catesbeiana tadpoles and frogs during metamorphosis

Anuran metamorphosis is characterized by profound morphological changes including remodeling of tissues and organs. This transition is initiated by thyroid hormones (THs). However, the current knowledge of changing levels of THs during metamorphosis relies on pooled samples using methods known for high variability with sparse reporting of measured variation. Moreover, establishing a clear linkage between key gene expression bioindicators and TH levels throughout the metamorphic process is needed. Using state-of-the-art ultra-high performance liquid chromatography isotope-dilution tandem mass spectrometry, we targeted 12 THs and metabolites in the serum of Rana [Lithobates] catesbeiana (n=5-10) across seven distinct postembryonic stages beginning with premetamorphic tadpoles (Gosner stage 31-33) and continuing through metamorphosis to a juvenile frog (Gosner stage 46). TH levels were related to TH-relevant gene transcripts (thra, thrb, and thibz) in back skin of the same individual animals. Significant increases from basal levels were observed for thyroxine (T4) and 3,3,5-triiodothyronine (T3) at Gosner stage 41, reaching maximal levels at Gosner stage 44 (28{+/-}10 and 2.3{+/-}0.5 ng/mL, respectively), and decreasing to basal levels in juvenile frogs. In contrast, 3,5-diiodothyronine (T2) increased significantly at Gosner stage 40 and was maintained elevated until stage 44. While thra transcript levels remained constant and then decreased at the end of metamorphic climax, thrb and thibz were induced to maximal levels at Gosner stage 41, followed by a decrease to basal levels in the froglet. This exemplifies the exquisite timing of events during metamorphosis as classic early response genes are transcribed in anticipation of peak TH concentrations. The distinct T2 concentration profile suggests a biological role of this biomolecule in anuran postembryonic development and an additional aspect that may be a target of anthropogenic chemicals that can disrupt anuran metamorphosis and TH signalling. Hence, as a second aim of the study, we set out to find additional bioindicators of metamorphosis, which can aid future investigations of developmental disruption. Using a sensitive nanoLC-Orbitrap system an untargeted analysis workflow was applied. Among 6,062 endogenous metabolites, 421 showed metamorphosis-dependent concentration dynamics. These potential bioindicators included several carnitines, prostaglandins and some steroid hormones.

developmental biology↗

bioRxiv2020

Grandmother's chemical legacy of pesticide exposure: bi-generational effects and acclimation in a model invertebrate

Man-made chemicals are a significant contributor to the ongoing deterioration of ecosystems. Currently, risk assessment of these chemicals is based on observations in a single generation of animals, despite potential adverse intergenerational effects. Here, we investigate the effect of the fungicide prochloraz across three generations of Daphnia magna. We studied both the effects of continuous exposure over all generations and the effects of first-generation (F0) exposure on two subsequent, non-exposed, generations. Effects at different levels of biological organization were monitored. Acclimation to prochloraz was found after continuous exposure. Following F0-exposure, non-exposed F1-offspring showed no significant effects. However, in the F2 animals, several parameters differed significantly from controls. A direct association between grandmaternal effects and toxic mode of action of prochloraz was found, showing that chemicals can be harmful not only to the exposed generation, but also to subsequent generations and that effects may even skip a generation.

molecular biology↗

bioRxiv2019

Altered brain-wide auditory networks in fmr1-mutant larval zebrafish

Altered sensory processing is characteristic of several psychiatric conditions, including autism and fragile X syndrome (FXS). Here, we use whole-brain calcium imaging at cellular resolution to map sensory processing in wild type larval zebrafish and mutants for fmr1, which causes FXS in humans. Using functional analyses and graph theory, we describe increased transmission and reduced filtering of auditory information, resulting in network-wide hypersensitivity analogous to the auditory phenotypes seen in FXS.

neuroscience↗