Macrophages are involved in many aspects of both the innate and acquired immunity, and participate in tissue homeostasis, bone remodelling, wound healing, and tissue repair. When their function becomes dysregulated, they contribute to the initiation and progression of inflammatory diseases. Genes expressed in activated macrophages are likely to play an important role in inflammation and/or immunity. One family of genes that is highly expressed in activated macrophages is the Schlafen (Slfn) gene family. Given that very little is known about the function of this family, particularly in macrophages, this study focused on the regulation and function of one family member, namely Slfn-4. The transcriptional regulation of Slfn-4 was characterised in murine macrophages. The expression of Slfn-4 was transiently down regulated during macrophage differentiation and dramatically up regulated in response to activation signals including lipopolysaccharide (LPS) and dsRNA Poly(I:C). A potential association with inflammation was further suggested by the enhanced expression of Slfn-4 in a mouse model of rheumatoid arthritis. Further investigations into transcriptional regulation of Slfn-4 revealed that it belongs to the subset of genes that are type I interferon (IFN)-inducible. This finding is consistent with the predicted transcription factor binding sites in the putative promoter of Slfn-4, and suggests a role for Slfn-4 in the antiviral response. To gain further insight into the function of Slfn-4 in macrophage biology, in vitro over-expression approaches were undertaken and its cellular localisation in macrophages was characterised. In resting and activated macrophages, Slfn-4 exhibited a cytoplasmic and strong perinuclear localisation. Additional studies were carried out to investigate the in vivo biology of Slfn-4 in macrophages. For this purpose, the Csf1r-GAL4VP16/UAS-ECFP (referred to as “MacBlue”) transgenic mouse line was first characterised. Enhanced cyan fluorescent (ECFP) reporter expression in the MacBlue transgenic mice was specifically detected in cells of the mononuclear phagocyte system during embryonic development and adulthood. The MacBlue transgenic mouse line was next used to drive expression of Slfn-4 in cells of the myeloid lineage in vivo, and to examine the phenotype of this line. Specific over-expression of Slfn-4 in cells of the myeloid lineage in vivo altered the percentage of peripheral blood monocytes and caused extramedullary hematopoiesis. In summary, this thesis demonstrated that Slfn-4 expression is dynamically regulated during macrophage differentiation and activation, and the enforced Slfn-4 over-expression in cells of the myeloid lineage perturbs normal monocyte/macrophage development.
| Identifer | oai:union.ndltd.org:ADTP/254099 |
| Creators | Wendy van Zuijlen |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
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