Biology subjects

Meddle, S.

Publications and source records attributed to Meddle, S..

6 recordsLinked to original sources

bioRxiv2026

CSF1R-dependent macrophages control B cell development and function in the chicken immune system.

Acquired immunity in mammals depends upon capture and presentation of antigens by specialised macrophage populations in splenic marginal zone and lymph node sinuses and follicular dendritic cells (FDC) within germinal centres. Cells referred to as FDC in chickens express CSF1R, the receptor for macrophage colony-stimulating factor (CSF1) and IL34. We utilised single cell RNA-seq on CSF1R+ cells from chicken spleen to identify monocytes and two distinct populations of macrophages. TIMD4/C1Q/MAFB+ macrophages were enriched for expression of genes involved in iron metabolism. A MARCO/VSIG4+ population expressed SPIC, a transcription factor associated with red pulp macrophages in mammals but also expressed receptors (CR2) and trophic factors (TNFSF13, CXCL13) associated with mammalian FDC. SPIC+ cells were located within follicles in spleen, caecal tonsil and bursa. We generated a CSF1R knockout in the chicken germ line. Mutant birds lack macrophages in the embryo. They were indistinguishable from wild type at hatch and behaved and fed normally but from day 5-6 post hatch they failed to thrive. Loss of CSF1R function in hatchlings led to monocytopenia and granulocytosis and the loss of macrophage subpopulations in lymphoid organs. Consistent with their expression of B cell trophic factors, the loss of follicular macrophages in the bursa was associated with involution and severe B cell deficiency in the circulation and spleen. In summary, lymphoid tissues of chickens contain specialised macrophage populations with distinct expression profiles. The details of regulation by CSF1R, specialised functions and underlying transcriptional regulation are quite different between birds and mammals.

immunology↗

bioRxiv2025

Artificial Light at Night Disrupts Circadian and Metabolic Gene Expression in the Green Anole Lizard (Anolis carolinensis): A Transcriptomic Analysis

Artificial light at night (ALAN) disrupts natural light-dark cycles, posing ecological challenges for wildlife in urban areas. Here we investigated the effects of ALAN on gene expression in the brain, liver, and skin of green anole lizards (Anolis carolinensis) whose urban populations are increasingly exposed to light pollution. To identify genetic pathways impacted by ALAN exposure we analysed expression of genes associated with circadian and metabolic regulation at midday, midnight and at midnight with artificial light. Differential expression analysis revealed that clock-related genes (PER1, NR1D1, CRY2) were significantly altered in the brain, liver, and skin following ALAN treatment and genes involved in glucagon regulation (GCG) and lipid metabolism (NOCT) were differentially expressed in the liver, indicating metabolic disruptions. Skin exhibited unique responses to ALAN suggesting that repair responses may be altered as genes related to cellular processes, such as wound healing, were upregulated under normal light and dark conditions. Our findings also show that ALAN disrupts core circadian genes, impacting physiological processes including hormone regulation, glucose homeostasis, and potentially reproductive cycles. This study provides the first transcriptomic evidence of the effects of light pollution on green anoles, highlighting the need to preserve natural light cycles in urban habitats. An interactive online database developed for this study allows further exploration of gene expression changes, to promote research on artificial light-polluted environments.

genetics↗

bioRxiv2025

Expression of Non-Visual Opsins in the Green Anole Lizard (Anolis carolinensis)

Extra-retinal photoreception is widely observed across vertebrates, facilitating species-specific regulation of physiological and behavioral responses to diverse photic environments. Yet, the roles of non-visual opsins remain poorly understood, as their distribution and function have not yet been systematically investigated. This study provides the first comprehensive evidence of non-visual opsin expression across the reptile body. Using predicted sequences for extra-retinal photoreceptors, non-visual opsins were confirmed in the brain, eye, testes, liver, and skin. Specifically, OPN3 (encephalopsin) exhibited the highest expression across all tissues, particularly in the testes, corroborating findings in mammals. OPN5 (neuropsin) was detected predominantly in the testes, marking the first such report in reptiles. Moderate expression of OPN4 (melanopsin) in the brain and eye supports its roles in both visual and deep-brain photoreception. In the skin, a distinct pattern of higher opsin expression was observed in the dorsal skin compared to ventral skin. OPN3-3 was most abundant and exhibited a unique expression profile, potentially linking opsins to light-mediated processes influencing chromatophore-driven color changes. Findings from this research provide a critical evolutionary context for understanding the role and conservation of non-visual opsins in reptiles and their relevance to vertebrate lineages, including mammals and birds.

zoology↗

bioRxiv2021

Noradrenergic alpha-2A receptor activation suppresses courtship vocalization in male Japanese quail.

Male Japanese quail produce high-frequency crow vocalizations to attract females during the breeding season. The nucleus of intercollicularis (ICo) is the midbrain vocal center in birds and electrical stimulation of the ICo produces calls that include crowing. Noradrenaline plays a significant role in sexual behavior but the contribution of noradrenaline in the control of courtship vocalizations in quail has not been well established. Using dose-dependent intracerebroventricular injection of clonidine, an 2-adrenergic receptor- specific agonist, crowing vocalization was immediately suppressed. At the same time as crow suppression by clonidine there was a reduction of immediate early gene, zenk mRNA, in the ICo; no zenk mRNA expression was detected in the dorsomedial division of the nucleus. Using histochemistry, we determined that the ICo receives noradrenergic innervation and expresses 2A-adrenergic receptor mRNA. Taken together, these data suggest that noradrenaline regulates courtship vocalization in quail, possibly via the alpha2A- adrenergic receptor expressed on ICo neurons.

animal behavior and cognition↗

bioRxiv2020

Circadian clock mechanism driving mammalian photoperiodism

The annual photoperiod cycle provides the critical environmental cue synchronizing rhythms of life in seasonal habitats. In 1936, Bunning proposed a circadian-based coincidence timer for photoperiodic synchronization in plants. Formal studies support the universality of this so-called coincidence timer, but we lack understanding of the mechanisms involved. Here we show in mammals that long photoperiods induce the circadian transcription factor BMAL2, in the pars tuberalis of the pituitary, and triggers summer biology through the eyes absent / thyrotrophin (EYA3 / TSH) pathway. Conversely, long-duration melatonin signals on short photoperiods induce circadian repressors including DEC1, suppressing BMAL2 and the EYA3/TSH pathway, triggering winter biology. These actions are associated with progressive genome-wide changes in chromatin state, elaborating the effect of the circadian coincidence timer. Hence, circadian clock-pituitary epigenetic pathway interactions form the basis of the mammalian coincidence timer mechanism. Our results constitute a blueprint for circadian-based seasonal timekeeping in vertebrates.

molecular biology↗

bioRxiv2019

Odour conditioning of positive affective states: Rats can learn to associate an odour with being tickled

Most associative learning tests in rodents use negative stimuli, such as an electric shock. We investigated if young rats can learn to associate the presence of an odour with the experience of being tickled (i.e. using an experimenters hand to mimic rough-and-tumble play), shown to elicit 50 kHz ultrasonic vocalisations (USVs), which are indicative of positive affect. Male, pair-housed Wistar rats (N=24) were all exposed to two neutral odours (A and B) presented in a perforated container on alternate days in a test arena. Following 60s of exposure, the rats were either tickled on days when odour A (n=8) or odour B (n=8) was present, or never tickled (n=8). When tickled, rats produced significantly more 50 kHz USVs compared to the days when not being tickled, and compared to control rats. The level of anticipatory 50 kHz USVs in the 60s prior to tickling did not differ significantly between the tickled and control rats. Following the odour conditioning, rats were exposed successively in the same arena to three odours: an unknown neutral odour, extract of fox faeces, and either odours A or B. Compared to controls, 50 kHz USVs of tickled rats increased when exposed to the odour they had previously experienced when tickled, indicating that these rats had learned to associate the odour with the positive experience of being tickled. In a test with free access for 5 min to both arms of a T-maze, each containing one of the odours, rats tickled with odour A spent more time in the arm with this odour. This work is the first to test in a fully balanced design whether odours can be conditioned to tickling, and indicates that positive odour conditioning has potential to be used as an alternative to negative conditioning tests.

animal behavior and cognition↗