Biology subjects

Herget, U.

Publications and source records attributed to Herget, U..

3 recordsLinked to original sources

bioRxiv2025

Next-generation hybridization chain reaction tools with enhanced sensitivities to detect challenging targets

Compared to traditional enzyme-based in situ amplification methods, Hybridization Chain Reaction v3.0 (HCR v3.0) offers high specificity for spatial RNA visualization but lacks the sensitivity required to robustly detect short or low-abundance targets, particularly in thick tissue with high autofluorescence. Here, we describe three HCR variants that combine the specificity of HCR v3.0 with additional signal amplification through catalytic reporter deposition (HCR-Cat), immunostaining (HCR-Immuno), or iterative HCR and immunodetection (HCR-Multi). These methods substantially enhance detection sensitivity, enabling robust spatial visualization of low-abundance transcripts, improved performance in challenging tissue environments, and compatibility with fluorescence- and alkaline phosphatase-based chromogenic detection. These methods enable transcript-resolution imaging, even when using a limited number of probes, thereby expanding the range of biological applications accessible to HCR.

neuroscience↗

bioRxiv2025

Pth4 neurons define a novel hypothalamic circuit that promotes sleep via brainstem monoaminergic neurons

Classical studies identified a critical role for the hypothalamus in regulating sleep and wake states, but few such hypothalamic neuronal populations have been identified. Here we describe a sleep-promoting population of hypothalamic neurons that expresses the neuropeptides QRFP and parathyroid hormone 4 (Pth4) in zebrafish. Optogenetic stimulation of these neurons results in a large increase in sleep that requires pth4 but not qrfp. Noradrenergic locus coeruleus (LC) neurons and serotonergic raphe neurons (RN) in the hindbrain express distinct pth receptors, and genetic epistasis and cell ablation experiments revealed that Pth4 neuron-induced sleep is suppressed in mutants that lack noradrenaline in the LC or lack the serotonergic RN. Pth4 neuron-induced sleep is also suppressed in serine/threonine kinase 32a (stk32a) mutants, possibly via stk32a-expressing neurons in the prethalamus that express pth receptors. These results identify QRFP/Pth4 neurons as a novel hypothalamic sleep-promoting population and support a model in which distinct sleep- and wake-promoting hypothalamic populations act via monoaminergic neurons in the hindbrain to control vigilance state.

neuroscience↗

bioRxiv2024

Early life challenge enhances cortisol regulation in zebrafish larvae

The hypothalamic-pituitary-adrenal (HPA) axis in mammals and the hypothalamic-pituitary-interrenal (HPI) axis in fish are open systems that adapt to the environment during development. Little is known about how this adaptation begins and regulates early stress responses. We used larval zebrafish to examine the impact of prolonged forced swimming at 5 days post-fertilization (dpf), termed early-life challenge (ELC), on cortisol responses, neuropeptide expression in the nucleus preopticus (NPO), and gene transcript levels. At 6 dpf, ELC-exposed larvae showed normal baseline cortisol but reduced reactivity to an initial stressor. Conversely, they showed increased reactivity to a second stressor within the 30-minute refractory period, when cortisol responses are typically suppressed. ELC larvae had fewer corticotropin-releasing hormone (crh), arginine vasopressin (avp), and oxytocin (oxt)-positive cells in the NPO, with reduced crh and avp co-expression. Gene expression analysis revealed upregulation of genes related to cortisol metabolism (hsd11b2, cyp11c1), steroidogenesis (star), and stress modulation (crh, avp, oxt). These results suggest that early environmental challenge initiates adaptive plasticity in the HPI axis, tuning cortisol regulation to balance responsiveness and protection during repeated stress. Future studies should explore the broader physiological effects of prolonged forced swimming and its long-term impact on cortisol regulation and stress-related circuits. SummaryThis study explores how early-life challenges in zebrafish affect stress responses and hormone regulation, offering insights into developmental adaptability and stress management mechanisms.

physiology↗