Biology subjects

Eachus, H.

Publications and source records attributed to Eachus, H..

4 recordsLinked to original sources

bioRxiv2023

Developmental Glucocorticoid exposure in zebrafish primes expression of genes linked to human psychiatric disorders

Early life stress (ELS) is one of the strongest risk factors for developing psychiatric disorders in humans. As conserved key stress hormones of vertebrates, glucocorticoids (GCs) are thought to play an important role in mediating the effects of ELS exposure in shaping adult phenotypes. In this process, early exposure to high level of GCs may induce molecular changes that alter developmental trajectory of an animal and primes differential adult responses. However, comprehensive characterization of identities of molecules that are targeted by developmental GC exposure is currently lacking. In our study, we describe lifelong molecular consequences of high level of developmental GC exposure using an optogenetic zebrafish model. First, we developed a new double-hit stress model using zebrafish by combining exposure to a high endogenous GC level during development and acute adulthood stress exposure. Our results establish that similar to ELS-exposed humans and rodents, developmental GC exposed zebrafish model shows altered behavior and stress hypersensitivity in adulthood. Second, we generated time-series gene expression profiles of the brains in larvae, in adult, and upon stress exposure to identify molecular alterations induced by high developmental GC exposure at different developmental stages. Third, we identify a set of GC-primed genes that show altered expression upon acute stress exposure only in animals exposed to a high developmental GC. Interestingly, our datasets of GC primed genes are enriched in risk factors identified for human psychiatric disorders. Lastly, we identify potential epigenetic regulatory elements and associated post-transcriptional modifications following high developmental GC exposure. Thus, we present a translationally relevant zebrafish model for studying stress hypersensitivity and alteration of behavior induced by exposure to elevated GC levels during development. Our study provides comprehensive datasets delineating potential molecular targets underlying the impact of developmental high GC exposure on adult responses.

neuroscience↗

bioRxiv2023

Elevated Glucocorticoid alters the trajectory of hypothalamic development and function

Exposure to excess glucocorticoid (GC) during early development is implicated in adult dysfunctions. Reduced adult hippocampal neurogenesis is a well-known consequence of exposure to early life stress or elevated GC, however the effects on neurogenesis during development and effects on other brain regions are not well understood. Using an optogenetic zebrafish model, here we analysed the effects of GC exposure on neurogenesis during development in the whole brain. We identify that the hypothalamus is a highly GC-sensitive region where elevated GC causes precocious development. This is followed by failed maturation and early decline accompanied by impaired feeding, growth, and longevity. In GC-exposed animals, the developmental trajectory of hypothalamic progenitor cells is strikingly altered, potentially mediated by direct regulation of transcription factors such as rx3 by GC. Our data provide cellular and molecular level insight into GC-induced alteration of the hypothalamic development trajectory, a process crucial for health across the life-course.

neuroscience↗

bioRxiv2022

Optogenetic induction of chronic glucocorticoid exposure in early-life impairs stress-response in larval zebrafish.

Organisms respond to stressors through a coordinated set of physiological and behavioural responses. Zebrafish provides an opportunity to study conserved mechanisms underlying the stress-response that is regulated largely by the neuroendocrine Hypothalamus-Pituitary-Adrenal/Interrenal (HPA) axis, with glucocorticoids (GC) as the final effector. In this study, we evaluated the effect of chronically active GC signalling in early life on the baseline and stress evoked GC(cortisol) levels in larval zebrafish. To this end, we employed an optogenetic actuator, Beggiatoa photoactivated adenylyl cyclase, expressed in the interrenal cells of zebrafish and demonstrate that its chronic activation leads to hypercortisolaemia and dampens the acute-stress evoked cortisol levels, across a variety of stressor modalities during early life. This blunting of stress-response, a phenotype reported by many studies to be observed in human subjects exposed to early-life trauma, was conserved in ontogeny at a later developmental stage. Furthermore, we observe a strong reduction of proopiomelanocortin (POMC)-expressing cells in the pituitary as well as global upregulation of FKBP5 gene expression, impinging on the negative feedback regulation elicited by elevated cortisol levels. Going forward, we propose that this model can be leveraged to tease apart the mechanisms underlying developmental programming of HPA axis by early-life stress and its implications for vulnerability and resilience to stress in adulthood.

neuroscience↗

bioRxiv2019

Regulation of neuron-specific gene transcription by stress hormone signalling requires synaptic activity in zebrafish

The Glucocorticoid Receptor (GR) co-ordinates metabolic and behavioural responses to stressors. We hypothesised that GR influences behaviour by modulating specific epigenetic and transcriptional processes in the brain. Using the zebrafish as a model organism, the brain methylomes of wild-type and grs357 mutant adults were analysed and GR-sensitive, differentially methylated regions (GR-DMRs) were identified. Two genes with GR-DMRs exhibited distinct methylation and transcriptional sensitivities to GR: the widely expressed direct GR target fkbp5 and neuron-specific aplp1. In larvae, neural activity is required for GR-mediated transcription of aplp1, but not for that of fkbp5. GR regulates metabotropic glutamate receptor gene expression, the activities of which also modulated aplp1 expression, implicating synaptic neurotransmission as an effector of GR function upstream of aplp1. Our results identify two distinct routes of GR-regulated transcription in the brain, including a pathway through which GR couples endocrine signalling to synaptic activity-regulated transcription by modulating metabotropic glutamate receptor expression.

developmental biology↗