The RNA modification N 6 -methyladenosine (m 6 A) influences mRNA stability and cell-type-specific developmental programming, and is highly abundant in the adult brain. However, it has not been determined whether m 6 A is dynamically regulated by experience.

Background RNA-directed regulation of epigenetic processes has recently emerged as an important feature of mammalian differentiation and development. Perturbation of this regulatory system in the brain may contribute to the development of neuropsychiatric disorders. Methods RNA sequencing (RNA-seq) was used to identify changes in the experience-dependent expression of long non-coding RNAs (lncRNAs) within the medial prefrontal cortex (mPFC) of adult mice. Transcripts were validated by real-time quantitative PCR and a candidate lncRNA, Gomafu, was selected for further investigation. The functional role of this schizophrenia-related lncRNA was explored in vivo by antisense oligonucleotide-mediated gene knockdown in the mPFC, followed by behavioral training and assessment of fear-related anxiety. LncRNA-directed epigenetic regulation of gene expression was investigated by chromatin and RNA immunoprecipitation assays. Results RNA-seq analysis revealed changes in the expression of a significant number of genes related to neural plasticity and stress, as well as the dynamic regulation of lncRNAs. In particular, we detected a significant down-regulation of Gomafu lncRNA. Our results revealed that Gomafu plays a role in mediating anxiety-like behavior, and suggest that this may occur through an interaction with a key member of the polycomb repressive complex 1, BMI1, which regulates the expression of the schizophrenia-related gene beta crystallin (Crybb1). We also demonstrated a novel role for Crybb1 in mediating fear-induced anxiety-like behavior. Conclusion Experience-dependent expression of lncRNAs plays an important role in the epigenetic regulation of adaptive behavior, and the perturbation of Gomafu may be related to anxiety and the development of neuropsychiatric disorders.

Non-coding RNAs (ncRNAs) have emerged as critical regulators of transcription, epigenetic processes, and gene silencing, which make them ideal candidates for insight into molecular evolution and a better understanding of the molecular pathways of neuropsychiatric disease. Here, we provide an overview of the current state of knowledge regarding various classes of ncRNAs and their role in neural plasticity and cognitive function, and highlight the potential contribution they may make to the development of a variety of neuropsychiatric disorders, including schizophrenia, addiction, and fear-related anxiety disorders.

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Consumption of palatable foods high in refined carbohydrate has been implicated as a contributing factor to the epidemic levels of obesity. Such foods may disrupt appetite regulation in the hypothalamus through alterations in hunger and satiety signalling. This investigation examined whether a palatable high refined carbohydrate (HRC) diet with the potential to induce obesity was linked to modulation of serotonin and dopamine signalling within the hypothalamus of rats. Male Wistar rats were allowed ad libitum access to either a palatable refined carbohydrate enriched (HRC) diet or standard chow (SC). Visceral fat percentage was used as a measure of the animals' weight gain during the trial. Real-time PCR was applied to determine any variation in levels of expression of the serotonin (Slc6A4 or Sert) and dopamine transporter (Slc6A3 or Dat) genes. After 29 weeks, the HRC group showed a significant increase in visceral fat percentage accompanied by increased expression of Sert. Higher levels of circulating triglycerides were also seen. This investigation determined that a refined high carbohydrate diet is associated with visceral obesity, increased circulating lipids in the blood and distorted serotonergic signalling, which possibly alters satiety and hunger signals.

Non-coding RNA (ncRNA)-directed regulation of epigenetic processes has recently emerged as an important feature of mammalian differentiation and development. Long non-coding RNAs (lncRNAs) are non-protein coding transcripts longer than 200 nucleotides RNAs. Although they are highly expressed within the mammalian brain, their function in behaviour remains equivocal.Deregulation of the lncRNA regulatory systems in the brain may contribute to the development of neuropsychiatric disorders.This project aimed to identify the role of lncRNAs in association with complex mammalian behaviours.In this thesis, sequencing technologies were used to identify ncRNAs that are dynamically regulated in fear-related learning in mice. These technologies included nuclear enriched RNA-capture sequencing, whole-genome RNA sequencing (RNA-Seq) and small RNA-Seq. The use of complementary sequencing approaches was expected to cover the expression of all possible sizes of ncRNAs. RNA-capture sequencing was used to identify newly described ncRNAs transcripts within the brain-derived neurotrophic factor (Bdnf) locus that were modulated in association with fear conditioning. Whole-genome RNA-Seq analysis showed that several lncRNAs (such as Neat1, Malat1, Mirg, Rmst and Gomafu) were dynamically regulated in response to fear learning. This transcriptome profiling revealed that most of the transcribed lncRNAs were proximal to coding genes, which suggested in cis regulatory activity of these transcripts. Knock down of the antisense lncRNA to Cacng2 altered the level of Cacng2 mRNA expression, which indicated the potential role of lncRNAs in regulating proximal coding genes in response to neural activation and behaviour.To establish the relevance of lncRNAs in association with behaviour, this investigation focused on Gomafu, which has previously been linked to schizophrenia, drug addiction and brain development.To determine whether Gomafu affects behaviour, chimeric antisense oligonucleotides (ASOs) were designed to knock down this lncRNA in vivo. Infusion of ASO in the mouse mPFC did not affect fear-associated long-term memory but instead appeared to modulate the level of anxiety.The molecular mechanisms by which Gomafu exerts its function in the development of anxietyrelated behaviours were explored further. A possible in cis regulatory function of Gomafu within the schizophrenia locus was investigated by examining the level of expression of proximal genes after Gomafu knockdown. Gomafu knockdown resulted in the up-regulation of Crybb1, gene that is antisense to the Gomafu lncRNA. Previous investigations have suggested that lncRNAs regulate the II expression of coding genes in association with Polycomb group repressive complexes (PRCs).Immunoprecipitation assays were performed to investigate the molecular interplay between Gomafu and Crybb1 through PRCs. Gomafu recruited PRC1 to the Crybb1 promoter, which regulated Crybb1 expression levels in response to neuronal stimulation. Experimental knock down of Crybb1 also exposed that its expre...