Anatomy and Neuroscience - Theses
Permanent URI for this collection
Search Results
1 - 2 of 2
-
ItemTranscriptomic diversification along the monocyte-macrophage continuum.( 2019)Current models of innate immune responses describe hard wired, gene-centric signalling networks, with limited capacity to define the molecular mechanisms underpinning transcriptomic diversity. It is well established that a transcriptional spectrum of responses accompanies acute macrophage activation, however it is unclear whether this spectrum originates in monocytes and to what extent it continues throughout reinfection. The contribution of molecular mechanisms such as enhancers and alternative transcription start sites is also undetermined. Given the critical roles that myeloid cells play in directing acute infection and priming adaptive immunity, it is important the regulation of their responses be understood. This thesis employed bioinformatic analysis of Cap Analysis Gene Expression (CAGE) and microarray data to describe transcriptional diversity along the monocyte-macrophage continuum. Using CAGE to map transcription start sites for capped RNAs, this thesis has shown that pathogen-specific transcriptional diversification commences early in monocyte infection (Chapters Three and Four) and continues throughout acute macrophage infection (Chapter Five). Transcriptomic diversity during acute infection was the product of kinetic and pathogen-specific engagement of distinct transcription start sites. Engagement of multiple transcription start sites drove responsiveness by regulating expression amplitude in functionally focused inflammatory gene sets and diversifying secondary response networks via expression of distinct protein isoforms. Chapter Six extended these studies of acute infection, demonstrating that transcriptional phenotypes continue to diversify during reinfection. These findings highlight the importance of studying innate immune responses at the isoform level and prompt the need to revise current models of innate immune signalling, such that monocyte-macrophage biology should no longer be modelled as a series of static states, but rather, as a continually evolving continuum.
-
ItemTAM signalling in CNS demyelination and multiple sclerosis( 2015)Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS). Involvement of the immune system in the pathogenesis of MS is a key feature of the disease, and an understanding of the mechanisms underlying how immune responses are shaped during CNS demyelination will provide insight into the development of new therapeutic strategies. The TAM (Tyro3, Axl, Mertk) family of receptor tyrosine kinases and their ligands Growth Arrest-Specific 6 (Gas6) and Protein S (ProS) have been shown to modulate many immunological processes important during central demyelination. The major aim of this thesis is to provide further insight into TAM biology in the context of both an animal model of inflammatory demyelination and human MS. By conducting a study examining MS patients and common genetic variations within TAM genes, I identified the MERTK gene as a novel MS susceptibility gene. Examination of plasma from MS patients revealed that levels of the TAM ligand PROS are decreased in MS and that low PROS levels are associated with increased MS disease severity. To interrogate the role of TAM signalling in modulating disease severity during inflammatory demyelination, I used the experimental autoimmune encephalomyelitis (EAE) animal model and observed major changes in TAM gene expression within the CNS and peripheral immune cells during EAE. Examination of Gas6-/- mice during EAE showed that absence of the TAM receptor ligand Gas6 results in both attenuated microglial/macrophage responses and disease severity during the effector phase of EAE. Conditional deletion of Mertk from dendritic cells (DC) resulted in worse disease during the effector phase of EAE. Stratification by sex revealed sexual dimorphism in TAM gene expression and also in the outcome of EAE in both Gas6-/- mice and mice with DC-specific deletion of Mertk. In summary, the data presented in this thesis suggest that the TAM family plays key roles in MS susceptibility and modulating innate immune responses during inflammatory demyelination, providing evidence for members of the TAM family as either markers of disease severity and/or therapeutic targets for the treatment of MS.