Project description:The Glucocorticoid Receptor (GR) co-ordinates metabolic and behavioural responses to stressors. We hypothesised that GR influences behaviour by modulating 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. DMRs linked to genes with biologically salient functions were selected for confirmatory deep sequencing analysis in wild-type and GR mutant 5dpf larval heads, using the BisPCR2 technique (Bernstein et al., 2015). Our results demonstrate that the genes fkbp5 and aplp1 exemplify two distinct modes of GR-regulated, glucocorticoid-responsive DNA methylation in the brain.
Project description:The glucocorticoid receptor (GR) regulates gene expression upon activation by glucocorticoid (GC) hormones. In zebrafish, two GR splice variants exist: the canonical GR α-isoform (GRα), and the GR β-isoform (GRβ). The exact function of GRb remains elusive. We have investigated the transcriptional role of GRa and GRb in the zebrafish embryo model by injecting mebryos with two splice-blocking morpholinos (one leading to knockdown of both GR α- and β-isoforms, and another targeting the alternative splicing of the GR pre-mRNA in favor of the GR β-isoform) and with GRβ mRNA (resulting in specific GRβ overexpression). Transcriptome profiling was performed on total RNA isolated from 30 hpf embryos. Our results show that GRb does not act as a dominant-negative inhibitor of GRa, and that GRa regulates two distinct gene clusters, which are mainly involved in the metabolism of the embryo.
Project description:The glucocorticoid receptor (GR) regulates gene expression upon activation by glucocorticoid (GC) hormones. In zebrafish, two GR splice variants exist: the canonical GR M-NM-1-isoform (GRM-NM-1), and the GR M-NM-2-isoform (GRM-NM-2). The exact function of GRb remains elusive. We have investigated the transcriptional role of GRa and GRb in the zebrafish embryo model by injecting mebryos with two splice-blocking morpholinos (one leading to knockdown of both GR M-NM-1- and M-NM-2-isoforms, and another targeting the alternative splicing of the GR pre-mRNA in favor of the GR M-NM-2-isoform) and with GRM-NM-2 mRNA (resulting in specific GRM-NM-2 overexpression). Transcriptome profiling was performed on total RNA isolated from 30 hpf embryos. Our results show that GRb does not act as a dominant-negative inhibitor of GRa, and that GRa regulates two distinct gene clusters, which are mainly involved in the metabolism of the embryo. This microarray study was designed to determine the effect of knockdown and overexpression of GRa and GRb. For this purpose, wild type (AB/TL) zebrafish embryos were injected at the 1-2 cell stage with a standard control morpholino (SC-MO), a splice-blocking morpholino leading to knockdown of both GR M-NM-1- and M-NM-2-isoforms (MO1), a splice-blocking morpholino targeting the alternative splicing of the GR pre-mRNA in favor of the GR M-NM-2-isoform (MO2), or GRb mRNA. At 24 hpf, each group was treated with dexamathasone (or vehicle) for 6 hr. This resulted in 8 treament groups: SC-MO/veh, SC-MO/dex, MO1/veh, MO1/dex, MO2/veh, MO2/dex, GRb mRNA/veh, GRb mRNA/dex. After the incubation period, embryos were collected and RNA was isolated from 20 embryos per treatment group (30 hpf). Three individual experiments were performed, and the resulting triplicate samples were analyzed by microarray, using a common reference approach.
Project description:To further characterize the roles of cortisol signaling via the glucocorticoid receptor (GR) in developing zebrafish, we have used morpholino oligonucleotides to knockdown GR protein translation and measured gene expression in RNA extracted from 24 and 36 hours post fertilization (hpf) embryos. The GR morpholino was characterized previously in Nesan et al., 2012, Endocrinology 181, 35-44) Single-cell zebrafish embryos were microinjected with either active morpholino or mispair control. Embryos were frozen at 24 and 36 hpf and total RNA extracted for microarray analysis. Three independent replicates (different breeding events on separate days) were performed for each treatment per timepoint.
Project description:To further characterize the roles of cortisol signaling via the glucocorticoid receptor (GR) in developing zebrafish, we have used morpholino oligonucleotides to knockdown GR protein translation and measured gene expression in RNA extracted from 24 and 36 hours post fertilization (hpf) embryos. The GR morpholino was characterized previously in Nesan et al., 2012, Endocrinology 181, 35-44)
Project description:The Glucocorticoid Receptor (GR) is a transcriptional regulator which co-ordinates behavioural, metabolic and immune responses to stressors. Previous studies have shown that wild-type and grs357 mutant zebrafish exhibit a range of behavioural differences, implying possible roles for GR function in the brain. As part of a study to elucidate the mechanisms underlying the behaviours that are regulated by GR, we compared the brain transcriptomes of wild-type and grs357 mutant adults. RNA-seq analysis identified 19 Biological Process and 4 Molecular Function Gene Ontology (GO) terms that were particularly sensitive to loss of GR function. Foremost among the Biological Process terms linked to GR function are Chaperone-mediated Protein Folding, Regulation of Circadian Rhythm and Regulation of Primary Metabolic Process, each of which is accompanied by several other closely related GO terms. In addition, the Biological Process GO term Behavior was significantly associated with 32 genes exhibiting GR-regulated gene transcription. The Molecular Function terms most closely linked to GR function are Heat Shock Protein Binding, Protein Serine/Threonine Kinase Activity, Transcription Regulator Activity and Unfolded Protein Binding. Taken together, our results identify key biological processes and novel molecular mechanisms through which the GR likely regulates responses to stress in the zebrafish adult brain.
Project description:RNA-Seq comparing transcript expression in the brains of 3 dj-1-/- mutant zebrafish and 3 wild type siblings at 16 weeks post fertilisation.
Project description:In zebrafish, ovulated oocytes contain both cortisol deposited from the maternal circulation and maternal mRNA for the glucocorticoid receptor (gr mRNA), which is spread as granular structures throughout the central ooplasm. At the 1-cell stage (0.2 hpf), this transcript is relocated by streamers in the blastodisc area and equally partitioned among blastomeres. At 15 hpf, it is replaced by the zygotic transcript. Morpholino knockdown was applied to block translation (grATG1MO or MO2-nr3c1 and grATG2MO or MO3-nr3c1) of both maternal and zygotic gr transcripts, while a missplicing morpholino (grmismMO or MO4-nr3c1) was used to block post-transcriptionally the zygotic transcript alone. MO2-nr3c1 and MO3-nr3c1 (but not MO4-nr3c1) treatment produced craniofacial and caudal malformations in 1-dpf embryos and 5-dpf larvae, which were also affected by pericardial oedema, persistent yolk sac, reduced subintestinal veins, altered neurogenesis and uninflated swim bladder. Such effects were rescued with trout gr2 mRNA. Pangenomic microarray analysis revealed that 114 and 37 highly expressed transcripts were up- and down-regulated, respectively, by maternal GR protein deficiency in 5-hpf embryos. Similar alterations were found at 10 hpf. These effects were confirmed by real-time PCR of 2 up- (casp8, grp1 and igf2a) and 1 down-regulated transcripts (mcm6) evaluated at 4, 8 and 12 hpf. As the contents of transcripts were modified already at 4 hpf, it seems that the lack of GR affects both ways the molecular machinery for the degradation of maternal mRNAs. These results indicate that the maternal gr transcript participates in the maternal programming of zebrafish development. MO2-nr3c1 morphants were compared with MO2-nr3c1-5m morphants at 5 hpf and 10 hpf. MO2-nr3c1 morphants were compared with wild type (WT) at 5 hpf and 10 hpf. MO2-nr3c1 is a morpholino selected to knockdown translation of gr mRNA. MO2-nr3c1-5m is a specific control morpholino.
Project description:In zebrafish, ovulated oocytes contain both cortisol deposited from the maternal circulation and maternal mRNA for the glucocorticoid receptor (gr mRNA), which is spread as granular structures throughout the central ooplasm. At the 1-cell stage (0.2 hpf), this transcript is relocated by streamers in the blastodisc area and equally partitioned among blastomeres. At 15 hpf, it is replaced by the zygotic transcript. Morpholino knockdown was applied to block translation (grATG1MO or MO2-nr3c1 and grATG2MO or MO3-nr3c1) of both maternal and zygotic gr transcripts, while a missplicing morpholino (grmismMO or MO4-nr3c1) was used to block post-transcriptionally the zygotic transcript alone. MO2-nr3c1 and MO3-nr3c1 (but not MO4-nr3c1) treatment produced craniofacial and caudal malformations in 1-dpf embryos and 5-dpf larvae, which were also affected by pericardial oedema, persistent yolk sac, reduced subintestinal veins, altered neurogenesis and uninflated swim bladder. Such effects were rescued with trout gr2 mRNA. Pangenomic microarray analysis revealed that 114 and 37 highly expressed transcripts were up- and down-regulated, respectively, by maternal GR protein deficiency in 5-hpf embryos. Similar alterations were found at 10 hpf. These effects were confirmed by real-time PCR of 2 up- (casp8, grp1 and igf2a) and 1 down-regulated transcripts (mcm6) evaluated at 4, 8 and 12 hpf. As the contents of transcripts were modified already at 4 hpf, it seems that the lack of GR affects both ways the molecular machinery for the degradation of maternal mRNAs. These results indicate that the maternal gr transcript participates in the maternal programming of zebrafish development.
Project description:Forced sustained swimming exercise at optimal speed enhances growth in many fish species, particularly through hypertrophy of the white skeletal muscle. The exact mechanism of this effect has not been resolved yet. To explore the mechanism, we first subjected wild-type zebrafish to an exercise protocol validated for exercise-enhanced growth, and showed that exercised zebrafish, which indeed showed enhanced growth, had higher cortisol levels than the non-exercised controls. A central role was therefore hypothesized for the steroid hormone cortisol acting through the Glucocorticoid receptor (Gr). Second, we subjected wild-type zebrafish and zebrafish with a mutant Gr to exercise at optimal, suboptimal and super-optimal speeds and compared them with non-exercised controls. Exercised zebrafish showed growth enhancement at all speeds, with highest growth at optimal speeds. In the Gr mutant fish, exercise resulted in growth enhancement similar to wild-type zebrafish, indicating that cortisol cannot be considered as a main determinant of exercise-enhanced growth. Finally, the transcriptome of white skeletal muscle tissue was analysed by RNA sequencing. The results of this analysis showed that in the muscle tissue of Gr mutant fish a lower number of genes is regulated by exercise than in wild-type fish (183 versus 351). A cluster of 36 genes was regulated by exercise in both wild-type and mutant fish. In this cluster, genes involved in transcriptional regulation and protein ubiquitination were overrepresented. Since growth was enhanced similarly in both wild-type fish and mutants, these processes may play an important role in exercise-enhanced growth.