The mushroom body (MB) is the site of odor association learning in Drosophila.  In the canonical model, there are two types of reinforcing dopamine neurons (DANs): one set for rewarding unconditioned stimuli (US), and one responding to aversive US.  When DANs are activated together with an odor (the conditioned stimulus, or CS), plasticity is induced in the downstream output neurons (MBONs).  We have identified a DAN (V1) that surprisingly responds preferentially to odors, and responds weakly or not at all to various classical US.  In order to explore the relationship between V1 odor responses and the established roles of the MB, I characterized the responses of DAN V1, and probed its relationship to odor-driven behavior, associative conditioning, and activity in other MB compartments. These data show that V1 receives recurrent input from identified MBONs, contributes to the activity of an MBON that enhances alerting behavior, and that its odor responses are modulated by conditioning. We therefore present the study of the alpha2 compartment, which V1 innervates, as the dissection of an atypical compartment of the MB, one that acts as a hub by which various information from other compartments and brain areas is integrated in order to alter a behavioral response to odor. This work furthers our understanding of the MB not simply as an engine of classical learning, but as a system of diverse interconnected modules that allow coordinated fine control of behavior.

The mammalian olfactory system is capable of decoding complex mixtures of volatile chemical odorants into identifiable percepts. While the general mode of peripheral signal transduction is largely known, the mechanism relies on a rather complicated combinatorial “olfactory code”, where each of the hundreds of expressed odorant receptors (ORs) detects multiple odorants, and a given odorant in turn activates multiple ORs (Malnic, Hirono et al. 1999). Since the first identification of mammalian ORs in 1991, the deorphanization, i.e. solving of the substrate, of ORs has proven to be a challenge. Many attempts at systematic monitoring of the olfactory code have seen marginal successes for a number of reasons. First of all, there are still no solved structures of mammalian ORs to be used for high throughput computational modeling. Second, experimental validation methods such as heterologous expression still face considerable challenges. Lastly, primary chemical features of odors that allow for OR tuning are not yet defined. The traditional organic chemistry-based classification of odorants fails to predict biological activity, while percept-based computational analyses isolate esoteric descriptors that are difficult to chemically manipulate. Receptor level structure-activity analysis can provide a missing context to the odorant discrimination in the peripheral olfactory system. A critical finding by Manic et al (1999) indicates that each mature olfactory sensory neuron (OSN) only expresses one type of OR, allowing for high throughput screening of carefully crafted odorant panels using dissociated OSN calcium imaging. A few bioisosteric substitutions widely utilized in medicinal chemistry were used to construct odorant panels, showing greater success in defining odorant-OR interaction than previously used organic chemistry-based clustering methods. Among classical substitutions used by medicinal chemists, heteroaromatic ring exchanges are especially well tolerated when heteroatoms with a similar topological polar surface area (TPSA) are used as replacements. Among odorants with differing TPSA, it is likely that an OR activated by analogous odorants at two extremes of the TPSA spectrum will be activated by an odorant with an intermediate TPSA. Flipping of a polar functional group, which is often used with amides in drug target replacements, is well tolerated by the ORs in esters. Furthermore, there is a predictable activation pattern relative to number of carbons in a hydrophobic chain uninterrupted by polar epitopes. Using binary mixtures, the OR activity can be further surveyed through enhancement or inhibition of OSN activation signals. Odorants activating a smaller subset of an OR population may also be binding to a larger subset of ORs, resulting in mixture inhibition. Specifically, this work indicates that extracted odorant fragments may be binding but not activating some of the OR repertoire of the original odorant. The concept of non-classical bioisosteres is applied to the OR repertoire using aliphatic and aromatic aldehydes. It appears that the specialized electronics of a fully conjugated benzene ring can in fact be dispensable, only acting as conformational restrictor of the odorant in most cases. Not only do analogous non-conjugated systems substitute well for benzaldehyde, but so do non-cyclic odorants possessing tiglic moieties. Conformationally restricted extractions act as more faithful replacements for larger molecules in a subset of ORs. While the dissociated OSN results alone have broad implications for binding patterns of GPCRs in general, simple behavioral tests in mice using the same odorant panels indicate concrete perceptual links to medicinal chemistry-based odorant discrimination. The results from the behavioral data suggest that there may be a maximum constraint for percent OSN activation for two sequentially presented odors to be interpreted as the “same”. The results open a window to exploring other medicinal chemistry-based substitutions. Furthermore, many methodological improvements have been made over the past decade to allow for increased efficiency of deorphanization and validation of ORs.

No description available.

Lui, Ki. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 163-171). / Abstracts in English and Chinese. / Abstract (English) --- p.i / Abstract (Chinese) --- p.v / Acknowledgements --- p.vii / Abbreviations --- p.ix / Table of Content --- p.x / Chapter Chapter 1. --- Introduction / Chapter 1.1 --- Overview and Endocrinology of hormones and hormone receptors --- p.1 / Chapter 1.2 --- Hormone receptors: membrane bounded receptors --- p.3 / Chapter 1.3 --- Hormone receptors: steroid nuclear receptors --- p.4 / Chapter 1.4 --- "Estrogen, estrogen receptor alpha and beta (ERa, ERβ) and prostate gland" --- p.6 / Chapter 1.5 --- Orphan nuclear receptors --- p.10 / Chapter 1.6 --- The first orphan receptors identified-estrogen receptor related receptors --- p.12 / Chapter 1.6.1 --- Estrogen receptor related receptor alpha (ERRα) --- p.13 / Chapter 1.6.2 --- Estrogen receptor related receptor alpha (ERRβ) --- p.17 / Chapter 1.6.3 --- Estrogen receptor related receptor alpha (ERRγ) --- p.19 / Chapter 1.7 --- Aim of study --- p.21 / Figure 1.1 Mechanism of activation of classical nuclear receptor by ligand --- p.23 / Figure 1.2 Distribution of ERa and ERβ in human body --- p.24 / Chapter Chapter 2. --- Methods and Materials / Chapter 2.1 --- Origin and supply of Noble rats --- p.25 / Chapter 2.2 --- Cell culture / Chapter 2.2.1 --- Cell lines and culture media --- p.26 / Chapter 2.2.2 --- Cell culture onto cover slips for immunohistochemistry --- p.27 / Chapter 2.3 --- RNA preparation / Chapter 2.3.1 --- Total RNA extraction --- p.27 / Chapter 2.3.2 --- mRNA extraction by Oligote´xёØ procedure --- p.29 / Chapter 2.3.3 --- mRNA extraction by Fast Track 2.0 procedure --- p.30 / Chapter 2.4 --- Molecular cloning by Rapid Amplification of cDNA Ends (RACE) / Chapter 2.4.1 --- Molecular cloning of rERRα --- p.31 / Chapter 2.4.2 --- Molecular cloning of rERRβ --- p.36 / Chapter 2.4.3 --- Molecular cloning of rERRγ --- p.42 / Chapter 2.5 --- Molecular cloning into pCRII TOPO cloning vector --- p.47 / Chapter 2.6 --- Sequencing analysis of DNA sequence by dRodamine® or BigDye® --- p.47 / Chapter 2.7 --- DNA sequence analysis --- p.49 / Chapter 2.8 --- Reverse transcription and RT-PCR --- p.49 / Chapter 2.9 --- Southern blotting analysis / Chapter 2.9.1 --- Preparation of DNA blot membrane --- p.51 / Chapter 2.9.2 --- Purification of DNA fragment from agarose gel for DIG-DNA labeling --- p.52 / Chapter 2.9.3 --- Preparation of the DIG-labeled DNA probe --- p.53 / Chapter 2.9.4 --- Membrane hybridization and colorimetric detection --- p.53 / Chapter 2.10 --- In-situ hybridization histochemistry / Chapter 2.10.1 --- Linearization of DNA plasmid --- p.55 / Chapter 2.10.2 --- Synthesis of riboprobe --- p.56 / Chapter 2.10.3 --- Hybridization and detection --- p.56 / Chapter 2.11 --- Western blotting analysis / Chapter 2.11.1 --- Protein extraction --- p.59 / Chapter 2.11.2 --- Casting of SDS-PAGE electrophoresis --- p.59 / Chapter 2.11.3 --- Polyacrylamide gel electrophoresis --- p.61 / Chapter 2.11.4 --- Protein blotting analysis --- p.61 / Chapter 2.12.1 --- Immunohistochemistry / Chapter 2.12.1 --- Histological preparation --- p.63 / Chapter 2.12.2 --- Immunohistochemistry --- p.64 / Table 1. List of culture media --- p.66 / Table 2. Primer sequences for RACE-PCR --- p.67 / Table 3. PCR conditions for RT-PCR --- p.68 / Table 4. Primer sequences for RT-PCR --- p.68 / Table 5. Reagent mixtures for linearization of the plasmid DNA --- p.69 / Table 6. Riboprobe synthesis by in-vitro transcription --- p.70 / Chapter Chapter 3. --- Results / Chapter 3.1 --- Cloning of full-length cDNA of rERRs by RACE-PCR --- p.71 / Chapter 3.2 --- Cloning of full-length cDNA of rERRα from rat ovary cDNA library --- p.72 / Chapter 3.3 --- Cloning of full-length cDNA of rERRβ from rat ventral prostate --- p.76 / Chapter 3.4 --- Cloning of full-length cDNA of rERRγ from rat prostate --- p.80 / Chapter 3.5 --- Expression distribution of ERRs detected by RT-PCR --- p.83 / Chapter 3.6 --- mRNA expression of ERRs detected by in-situ hybridization --- p.86 / Chapter 3.7 --- Protein expression of ERRa and ERRγ detected by western blotting --- p.87 / Chapter 3.8 --- Expression of ERRa and ERRγ detected by immunohistochemistry --- p.88 / Figure 3.1 Full-length DNA sequence of rERRα --- p.92 / Figure 3.2 Predicted amino acid sequence of rERRα --- p.93 / "Figure 3.3 DNA sequence alignment of rat, mouse and human ERRα" --- p.94 / "Figure 3.4 Amino acid sequence alignment analysis of rat, mouse and human ERRα" --- p.95 / Figure 3.5 Full-length DNA sequence of rERRβ --- p.96 / Figure 3.6 Predicted amino acid sequence of rERRβ --- p.97 / "Figure 3.7 DNA sequence alignment of rat, mouse and human ERRβ" --- p.98 / "Figure 3.8 Amino acid sequence alignment analysis of rat, mouse and human ERRβ" --- p.99 / Figure 3.9 Full-length DNA sequence of rERRγ --- p.100 / Figure 3.10 Predicted amino acid sequence of rERRγ --- p.101 / "Figure 3.11 DNA sequence alignment of rat, mouse and human ERRγ" --- p.102 / "Figure 3.12 Amino acid sequence alignment analysis of rat, mouse and human ERRγ" --- p.103 / Figure 3.13 Restriction enzyme cutting of full-length plasmids --- p.104 / Figure 3.14 Expression pattern of rERRα in male sex accessory sex glands by RT-PCR --- p.105 / Figure 3.15 Expression pattern of rERRα in urinary system and female sex organs by RT-PCR --- p.106 / Figure 3.16 Tissue expression of rERRα by RT-PCR --- p.107 / Figure 3.17 In-situ hybridization of ERRα in ovary --- p.108 / Figure 3.18 Western blotting of ERRα --- p.109 / Figure 3.19 Immunohistochemistry of ERRα in ovary --- p.110 / Figure 3.20 Expression pattern of rERRβ in male sex accessory sex glands by RT-PCR --- p.111 / Figure 3.21 Expression pattern of rERRβ in urinary system and female sex organs by RT-PCR --- p.112 / Figure 3.22 Tissue expression of rERRβ by RT-PCR --- p.113 / Figure 3.23 In-situ hybridization of ERRβ in rat prostate --- p.114 / Figure 3.24 Negative control of in-situ hybridization of ERRβ in rat prostate --- p.115 / Figure 3.25 Expression pattern of rERRγ in male sex accessory sex glands by RT-PCR --- p.116 / Figure 3.26 Expression pattern of rERRy in urinary system and female sex organs by RT-PCR --- p.117 / Figure 3.27 Tissue expression of rERRγ by RT-PCR --- p.118 / Figure 3.28 Expression pattern of rERRγ in different prostatic cancer cell lines and xenografts by RT-PCR --- p.119 / Figure 3.29 In-situ hybridization of ERRγ in rat prostate --- p.120 / Figure 3.30 Negative control of in-situ hybridization of ERRβ in rat prostate --- p.121 / Figure 3.31 Western blotting of ERRγ --- p.122 / Figure 3.32 Immunohistochemistry of ERRγ in ERRy-transfected MCF-7 cells --- p.123 / Figure 3.33 Immunohistochemistry of ERRγ in ventral prostate of rat --- p.124 / Figure 3.34 Immunohistochemistry of ERRγ in lateral prostate of rat --- p.125 / Figure 3.35 Immunohistochemistry of ERRγ in dorsal prostate of rat --- p.126 / Figure 3.36 Immunohistochemistry of ERRγ in testis of rat --- p.127 / Figure 3.37 Immunohistochemistry of ERRγ in epididymis of rat --- p.128 / Figure 3.38 Immunohistochemistry of ERRγ in brown adipose tissues of rat --- p.129 / Figure 3.39 Immunohistochemistry of ERRγ in brain of rat --- p.130 / Figure 3.40 Immunohistochemistry of ERRγ in brain of rat --- p.131 / Chapter Chapter 4. --- Discussion / Chapter 4.1 --- Sequence analysis of the full-length cDNA sequences of the rat estrogen receptor-related receptors (ERRs) --- p.132 / Chapter 4.2 --- Ligand independence and constitutive self-activation of estrogen receptor-related receptors --- p.133 / Chapter 4.3 --- Board expression pattern of estrogen receptor-related receptors --- p.138 / Chapter 4.3.1 --- Board expression pattern of estrogen receptor-related receptor alpha --- p.138 / Chapter 4.3.2 --- Board expression pattern of estrogen receptor-related receptor beta --- p.140 / Chapter 4.3.3 --- Board expression pattern of estrogen receptor-related receptor gamma --- p.141 / Chapter 4.4 --- Expression of ERRs in the prostate gland --- p.143 / Chapter 4.5 --- Expression of ERRs in the prostatic cell lines and cancer xenografts --- p.147 / Chapter 4.6 --- Expression of ERRs in the ERRγ-transfected MCF-7 cells --- p.149 / Chapter 4.7 --- Expression of ERRs in the testis and epididymis --- p.149 / Chapter 4.8 --- Expression of ERRs in the adipose tissue --- p.150 / Chapter 4.9 --- Expression of ERRs in the ovary --- p.151 / Chapter 4.10 --- Expression of ERRs in the brain --- p.153 / Figure 5.1 Map of full-length clone of rERRα --- p.155 / Figure 5.2 Map of full-length clone of rERRβ --- p.156 / Figure 5.3 Map of full-length clone of rERRα --- p.157 / Figure 5.4 Comparison of the homology of amino acid sequences amongst ERs and ERRs --- p.158 / Figure 5.5 Phylogeny tree of nuclear receptors --- p.159 / Figure 5.6 Relationship of different prostatic cell lines and xenografts --- p.160 / Chapter Chapter 5. --- Summary --- p.161 / References --- p.163-171

GRIN2A and GRIN2B encode the GluN2A and GluN2B subunits of the NMDA receptor, a subtype of ionotropic glutamate receptor that displays voltage-dependent block by Mg2+ and a high permeability to Ca2+. These receptors play important roles in synaptogenesis, synaptic transmission and synaptic plasticity, as well as contributing to neuronal loss and dysfunction in several neurological disorders. Recently, individuals with a range of childhood onset epilepsies, intellectual disability and other neurodevelopmental abnormalities have been found to carry heterozygous gene-disrupting or protein-altering point mutations in GRIN2A and GRIN2B. This thesis addresses the hypothesis that these point mutations cause key functional disturbances to NMDA receptor properties that contribute to neurodevelopmental disorders. To test this hypothesis, a group of related mutations were selected for functional assessment in heterologous systems: four missense mutations affecting residues in or near the subunit pore regions, all of which are associated with epilepsy and intellectual disability. To model the impact of gene disrupting mutations in GRIN2A, a preliminary analysis of the functional consequences of GluN2A haploinsufficiency in a genetically modified rat was also performed. Three of the four missense mutations were found to be associated with profound alterations in fundamental NMDA receptor properties: compared to wild type, GluN2AN615K was found to reduce Mg2+ block, GluN2BN615I and GluN2BV618G to cause potentiation by Mg2+, and GluN2AN615K and GluN2BN615I showed reduced conductance. GluN2AR586K was not found to influence the parameters assessed. When GluN2AN615K was expressed alongside wild type subunits in the same NMDA receptor, it was found to have a dominant negative effect. Finally, I established successful gene targeting in a new rat Grin2A knock-out model, and observed that heterozygous neurons had lower GluN2A protein expression and current density, making a good model to study human epilepsies associated with loss of a GRIN2A allele. This thesis provides evidence that three missense mutations in GRIN2A and GRIN2B affect physiologically important properties of the NMDA receptor, and that GluN2A haploinsufficiency influences important neural properties in vitro. This is consistent with these mutations causing disease and highlights these and related mutations as potential therapeutic targets in the future.

The nuclei of the midline thalamus are an important part of the brain’s limbic system. Previous work has described the presence of dopamine D2 receptors in the midline thalamus in humans, non-human primates, and rodents. A similar body of literature has also demonstrated dopaminergic innervation of the midline thalamus across these species. However, little is known regarding a) the source of dopaminergic innervation to the midline thalamus in rodents and b) the function of D2R in the midline thalamus in any species. I begin this thesis with a review of the literature examining the anatomy, electrophysiological properties, and role in behavior of the paraventricular nucleus of the thalamus (PVT), a region where D2R mRNA and protein is expressed. I next describe a series of three sets of experiments aimed toward examining the anatomical, electrophysiological, and behavioral role of D2R in the PVT in mice. In the first set of experiments, I used anatomical methods to show that D2R are particularly enriched in neurons of the PVT. I focused on D2R-expressing PVT neurons specifically and show their afferent and efferent projections throughout the brain. In addition, I describe a set of experiments aimed to establish a dopaminergic innervation to the PVT. In the second set of experiments, I used electrophysiological methods to study D2R-expressing PVT neurons. Here, I establish that tonic firing in D2R-expressing thalamic relay neurons in the PVT is inhibited by quinpirole, a D2R/D3R agonist, and increased by sulpiride, a D2R/D3R antagonist. In the third set of experiments, I assessed the behavioral function of D2R in PVT neurons since this has never been studied in any species. I directly manipulated PVT D2R in two directions: a) by overexpressing D2R, and b) by downregulating D2R. Here I show PVT D2R plays a role in both cocaine locomotor sensitization as well as contextual fear expression. Our findings demonstrate for the first time the role of D2R in the PVT and add to literature suggesting that the PVT is an important component of the neural circuitry underlying fear behavior and drug reward. I conclude this thesis with a discussion of the findings described in the three sets of experiments as well as a proposal for future experiments.

No description available.

No description available.

Glucocorticoids - cortisol and corticosterone - are steroid hormones synthesised in the adrenal gland that are important mediators of the stress response. Glucocorticoids are also vital in development to aid in organ maturation. Endogenous glucocorticoid levels rapidly rise before birth in all mammals to promote fetal organ maturation. Because preterm birth occurs before this natural rise in glucocorticoid levels, pregnant women at risk of preterm delivery are administered synthetic glucocorticoids to mature the fetal lung and aid neonatal survival. Mice that globally lack the glucocorticoid receptor (GR) die at birth, attributed to lung immaturity. Effects on tissues other than the lung remain less well characterised. Previous work has shown endogenous glucocorticoid action is also essential to mature the mouse fetal heart. Mice globally lacking GR have small, functionally and structurally immature hearts. Mice with tissue-specific deletion of GR in cardiomyocytes and vascular smooth muscle cells (SMGRKO mice; generated using Sm22α-Cre) also have an increased risk of death around the time of birth, suggesting that glucocorticoid maturation of the cardiovascular system is important for neonatal survival. GR expression within the fetal mouse heart initiates at E10.5 but GR in the myocardium is not activated and localised to the nucleus until E15.5. This suggests that mice can respond to glucocorticoid from E10.5. Here, it was hypothesised that antenatal glucocorticoid exposure, prior to the increase in endogenous glucocorticoid levels, would advance fetal heart maturation and this will depend on cardiovascular GR. To investigate the effects of antenatal glucocorticoid treatment on fetal heart maturation in mid-gestation and identify effects mediated by GR, mice with a conditional deletion of GR in cardiomyocytes and vascular smooth muscle cells were studied (SMGRKO mice). Pregnant mice received dexamethasone (dex) in the drinking water from E12.5-E15.5. Levels of Fkbp5 mRNA (a marker of glucocorticoid action) were unchanged between control and SMGRKO mice at E15.5 or following dex treatment. This suggested a lack of response to dex treatment. However, liquid chromatography mass spectrometry measurement confirmed the presence of dex and its active metabolite 6- hydroxydexamethasone (6OHDex) in livers of E15.5 fetuses from dex treated dams (fetal: Dex 0.46 ± 0.1 ng/g, 6OHDex 13.6 ± 0.35 ng/g; dam: Dex 7.96 ± 3.65 ng/g, 6OHDex 4.75 ± 1.2 ng/g). Livers of fetuses exposed to dex had lower levels of the naturally occurring active glucocorticoid, corticosterone, compared to vehicle treated fetuses. This suggests HPA axis suppression in dex exposed fetuses. Maternal liver showed no significant difference in corticosterone levels between dex and vehicle treated mice, suggesting that whilst dex suppressed the HPA axis in fetuses, it did not in the dams. To determine any persistent effects of early antenatal dex treatment on fetal heart, a later time point in gestation, E17.5, was also assessed. At E17.5, 2-days following cessation of dex treatment, dex and its metabolites were undetectable in the fetal and maternal liver. However, corticosterone levels remained reduced in fetal liver at E17.5 in dex exposed animals (vehicle treated: 4.31 ± 0.47 ng/g, Dex treated: 1.72 ± 0.42 ng/g, p < 0.01), whilst levels in the dam liver did not differ from vehicle treated controls. This suggests prolonged HPA axis suppression following dex treatment, which reduced the natural late-gestation rise in glucocorticoids required for fetal organ maturation. To determine whether early antenatal dex treatment could advance fetal heart function, Doppler imaging with a Vevo 770 high frequency ultrasound imager was used. Isovolumetric contraction time, isovolumetric relaxation time and ejection time of the left ventricle were unaltered by dex treatment. However, at E15.5 the mitral deceleration index (MDI), a measure of diastolic function that takes into account loading conditions, was 1.5 fold lower in vehicle treated SMGRKO mice than control (Cre-) littermates (p < 0.05). This reduction in SMGRKO mice suggests glucocorticoids are required within the fetal cardiomyocytes and/or vascular smooth muscle cells to mature the diastolic function of the fetal heart. Dex exposure had no effect on MDI in SMGRKO fetuses, but reduced the MDI by 1.5 fold in control mice to similar levels as in SMGRKO mice (p < 0.05). RNA analysis revealed a trend (p=0.09) for reduced levels of Nr3c1 mRNA (encoding GR) in hearts of E15.5 control (Cre-) fetuses following dex treatment. Although this requires confirmation at the level of GR protein, this finding together with the lack of induction of the GR target, Fkbp5, suggests dex may cause glucocorticoid resistance through down-regulation of GR. At E17.5, 2-days following cessation of dex there were no changes in systolic parameters and the reduction in MDI found at E15.5, following dex, had normalised. Litter size was reduced (close to a 50% reduction) at E17.5 in dex treated mice. This was similar between SMGRKO and control fetuses. The cause of death was not established, but potentially could be due to the reduction in the natural rise in glucocorticoids at E17.5, previously shown to be important for fetal heart maturation. It is therefore possible that mice with more immature hearts may die before reaching E17.5. RNA analysis was undertaken to determine any mechanistic alterations following dex treatment, which could support fetal heart functional alterations found at E15.5. In contrast to expectation, dex also decreased expression of mRNA encoding the calcium handling proteins SERCA2a, NCX1, and CaV1.2 in E15.5 fetal mouse hearts in both control and SMGRKO mice (p < 0.05), compared with the respective vehicle treated mice. These proteins had previously shown to be induced by glucocorticoid action in cardiomyocytes. However, the similar down-regulation in both genotypes indicates this effect is not dependent on GR in cardiomyocytes. Lowered SERCA2a activity following dex treatment could contribute to the changes in MDI observed in control mice. Similarly, Scnn1a and Kcnj12 mRNA levels, previously found to be induced by glucocorticoids in cardiomyocytes, were down-regulated in the E15.5 fetal heart in vivo following dex. Collectively, these data are consistent with glucocorticoid resistance or down-regulation of glucocorticoid action in E15.5 fetal hearts following dex administration. Mutations in KCNJ12 are associated with long QT syndrome, which is characterised by a delayed repolarisation of the heart following each contraction. An altered relaxation of the fetal heart found in control mice following dex could therefore be due to a prolongation of the cardiac action potential, particularly with a delayed repolarisation, because of lower Kcnj12 expression. At E17.5, there were no significant differences in expression of calcium handling genes or ion channel mRNAs between genotypes or following earlier dex exposure. Thus, effects of dex on mRNA expression level may not persist, which could account for the lack of functional changes observed 2-days following cessation of treatment. Because effects seen in vivo with dex treatment were contrary to those predicted, and to further investigate the effect of dex upon calcium content, an in vitro model of primary fetal E15.5 cardiomyocytes was used. Cardiomyocytes were treated with dex for 24 hours and effects on membrane potential voltage changes and calcium transients measured. Following dex, isolated fetal cardiomyocytes showed an elongated repolarisation phase of the action potential (untreated: 120.45 ± 13.81 ms, Dex: 142.34 ± 12.97 ms, p < 0.01), and duration of calcium transients (untreated: 103.31 ± 13.78 ms, Dex: 120.43 ± 23.36 ms, p < 0.05). This assessment of fetal cardiomyocytes was preliminary work to aid in the understanding of mechanisms of fetal heart functional alterations associated with glucocorticoid regulation. The results suggest glucocorticoids may be important in regulating calcium levels. In summary, dex treatment in mice from E12.5-E15.5 did not advance fetal heart maturation. It reduced litter size at E17.5, irrespective of whether GR was expressed in cardiomyocytes or not. The normal late-gestation increase in endogenous glucocorticoid levels in the fetus was reduced by dex, even after treatment finished. / The suppression of corticosterone levels following antenatal dex may reduce maturation of the heart at E15.5 and could be responsible for the reduction in litter size. Downregulation of GR in the fetal heart, may be a mechanism that results in glucocorticoid resistance following antenatal dex treatment, which could explain the lack of beneficial effects of antenatal dex upon fetal heart maturation in these experiments in mice.

Cells defend their cytosol against pathogen invasion using cell-autonomous immunity. When pathogens enter the cytosol they can damage host endomembranes, causing the mislocalisation of host molecules not normally found in the cytosol that are sensed as Danger Associated Molecular Patterns (DAMPs). Glycans exposed on damaged endomembranes are detected by danger receptors such as Galectin8. Galectin8 is recognised by the autophagy cargo receptor NDP52, specifically targeting the bacteria to autophagy. I hypothesised that other proteins would also be recruited to damaged endomembranes, which may initiate downstream mechanisms involved in cell-autonomous immunity or endomembrane repair. Identifying novel damage recruited proteins (DRPs) is difficult due to the short-lived and dynamic nature of damaged endomembranes. Therefore, I developed an unbiased approach for the identification of novel DRPs by proximity-dependent biotinylation using the ascorbate peroxidise enzyme APEX. This approach preferentially labels proteins located at damaged endomembranes for subsequent identification by TMT mass spectrometry. Four enriched proteins CCDC50, FBXO21, STAMBP and PDCD6 were identified as novel damage recruited proteins, recognising damaged SCVs. An alternative form of cell-autonomous immunity is the induction of cell death, for example by pyroptosis. Cell death destroys the bacteria's replicative niche and exposes them to the extracellular space where they may be phagocytosed. I hypothesised that host cells might tag cytoplasmic bacteria with intracellular opsonins to assist in their phagocytosis following their release from host cells. However, my work revealed that intracellular Salmonella Typhimurium acquire phagocytosis protection, thus becoming internalised by phagocytes less efficiently than control bacteria. Phagocytosis protection was acquired rapidly after S.Typhimurium infection and was not observed with dead bacteria. Phagocytosis protection is only partially reversed by opsonisation in human serum. My results indicate that intracellular S.Typhimurium-induces an evasion mechanism to prevent its subsequent recognition by extracellular phagocytes.