Transcriptional regulation of neurodevelopmental and metabolic pathways by the psychiatric illness candidate gene NPAS3

The basic helix-loop-helix PAS domain transcription factor gene NPAS3 is a risk factor for psychiatric disorders. A knockout mouse model also exhibits behavioural and adult neurogenesis deficits consistent with human illness. To define the location and mechanism of NPAS3 aetiopathology immunofluorescent and transcriptomic approaches were used. Npas3 was co-localised with Dcx, but not other neurogenesis markers, in the hippocampal subgranular zone - the site of adult neurogenesis. This implied that NPAS3 might be involved in maturing, rather than proliferating, neuronal precursor cells. Microarray analysis revealed that the transcriptional activities of NPAS3 and its truncated form (C-terminal deletion) in the HEK293 cell line are sensitive to circadian rhythm context. The most highly up-regulated NPAS3 target gene, VGF, encodes secretory peptides with established roles in neurogenesis, depression and schizophrenia. VGF was one of many NPAS3 target genes also shown to be regulated by the SOX family of transcription factors, suggesting an overlap in neurodevelopmental pathways. The transcriptional repression of multiple glycolytic genes indicated that NPAS3 has a second role in metabolic regulation. This finding was also confirmed by collaboration with a metabolomics research group at the University of Strathclyde. SOX11, a transcription factor known to play a role in neuronal and glial cell differentiation, was shown to be down-regulated by NPAS3. The set of genes targeted by SOX11 and their ontologies were deduced by a microarray analysis in a SOX11 overexpressing HEK293 cell line. Regulated genes include a previously established SOX11 target, known markers of neurogenesis as well as genes implicated in neuropsychiatric disorders. Multiple histone and zinc finger genes are regulated by SOX11, many of which were located in two clusters on chromosomes 6 and 19. The chromosome 6 cluster lies within a region of the genome showing the strongest genetic association with schizophrenia. SOX11 may alter localised expression competence and its targets induce a complex programme of chromatin remodelling and downstream gene expression changes to achieve the mature neuronal phenotype. This thesis details how transcription factors are involved in biological processes linked to psychiatric illness. The dual neurodevelopmental and metabolic aspects of NPAS3 activity described here increase our understanding of aspects of neurogenesis relevant to mental illness and may explain the innate and medication-induced susceptibility to diabetes reported in psychiatric patients

Role of miR-140-3p and miR-140-5p in lung cancer invasion

The precursor of miR-140 is located on chromosome 16q22.1 and produces two mature single strands named miR-140-3p and miR-140-5p, which have been associated with several cancers including non-small cell lung cancer (NSCLC). I aim to investigate the differential expression of these two miR-140 strands in NSCLC and their roles in the invasion of lung cancer cells. My hypothesis is that these two miR-140 strands suppress the progression of the NSCLC by targeting specific gene transcripts. MiR-140-3p and miR-140-5p were downregulated in tissues from NSCLC patients and lung cancer cell lines (A549 and SK-MES-1). The sequencing of the miR-140 precursor indicated two DNA variants in SK-MES-1 cells but not in A549 cells. This might affect the biogenesis of its mature strands because the expression levels of both miR-140-3p and miR-140-5p were lower in SK-MES-1 than in A549 cells. Mimics of miR-140-3p and miR-140-5p reduced the invasive properties of A549 cells and enhanced their adhesion to laminin and collagen, two of the main components of the extracellular matrix. In SK-MES-1 cells, both miR-140-3p and miR-140-5p mimics reduced invasion but only miR-140-5p decreased the migration of the cells. The conditioned media from lung cancer cells treated with the miR-140-3p mimics impaired the tubule formation of primary endothelial cells, suggesting its role as an angiogenesis inhibitor. By using bioinformatic tools, the integrin β 3 (ITGB3) was predicted as a novel target of miR-140-3p, which was validated by Dual-Luciferase miRNA Target Expression Vectors and western blotting. By combining the global data from Kinex™ Antibody Microarray (with 878 antibodies) and RNA-Sequencing, I speculate that miR-140-3p inhibits lung cancer invasion and limits the angiogenic potential of the endothelial cells through the epidermal growth factor receptor (EGFR) signalling pathway. In contrast, miR-130-5p may target cyclin-dependent kinase 3 (CDK3) and sulfatase 2 (SULF2) in NSCLC