Patched-1 (Ptch1) is the primary receptor for Hedgehog (Hh) ligands and mediates both canonical and non-canonical Hh signalling. Previously, our lab identified that mice possessing a Ptch1 C-terminal truncation display blocked mammary gland development at puberty that is overcome by overexpression of activated c-src. Testing the hypothesis that this involves a direct interaction between Ptch1 and c-src, we identified through co-immunoprecipitation that Ptch1 and c-src associate in an Hh-dependent manner, and that the Ptch1 C-terminus regulates activation of c-src in response to Hh ligand. Since the effects of Ptch1 intracellular domain deletions on canonical Hh signalling are ill-defined, we assayed this through luciferase reporter assays and qRT-PCR. Transient assays revealed that the Ptch1 middle intracellular loop is required for response to ligand, while qRT-PCR from primary cells showed that C-terminal truncation impairs canonical Ptch1 function. Together, this indicates that the intracellular domains of Ptch1 mediate distinct canonical and non-canonical functions.

Patched-1 (Ptch1) is the primary receptor for Hedgehog (Hh) ligands and mediates both canonical and non-canonical Hh signalling. Previously, our lab identified that mice possessing a Ptch1 C-terminal truncation display blocked mammary gland development at puberty that is overcome by overexpression of activated c-src. Testing the hypothesis that this involves a direct interaction between Ptch1 and c-src, we identified through co-immunoprecipitation that Ptch1 and c-src associate in an Hh-dependent manner, and that the Ptch1 C-terminus regulates activation of c-src in response to Hh ligand. Since the effects of Ptch1 intracellular domain deletions on canonical Hh signalling are ill-defined, we assayed this through luciferase reporter assays and qRT-PCR. Transient assays revealed that the Ptch1 middle intracellular loop is required for response to ligand, while qRT-PCR from primary cells showed that C-terminal truncation impairs canonical Ptch1 function. Together, this indicates that the intracellular domains of Ptch1 mediate distinct canonical and non-canonical functions.

Aggressive fibromatosis is a benign fibroproliferative tumour that can occur as a sporadic lesion or a manifestation in patients with familial syndromes, such as familial adenomatous polyposis. Tumours are characterized by the stabilization of β-catenin and the activation of β-catenin-mediated transcription. Current treatment results are far from ideal, and recurrence rates are high. As a result, there remains a need for more effective therapeutic strategies. In this work, we demonstrate the effect of hedgehog signalling inhibition on aggressive fibromatosis tumour development and β-catenin modulation. We found that hedgehog inhibition decreased cell viability and proliferation as well as total β-catenin levels in human aggressive fibromatosis tumour cells in vitro. Furthermore, following hedgehog inhibition in Apc+/Apc1638N aggressive fibromatosis mouse model, the number and volume of the tumours formed was reduced. Together, this work suggests that hedgehog signalling inhibitor agents are potential candidates to effectively manage aggressive fibromatosis.

Aggressive fibromatosis is a benign fibroproliferative tumour that can occur as a sporadic lesion or a manifestation in patients with familial syndromes, such as familial adenomatous polyposis. Tumours are characterized by the stabilization of β-catenin and the activation of β-catenin-mediated transcription. Current treatment results are far from ideal, and recurrence rates are high. As a result, there remains a need for more effective therapeutic strategies. In this work, we demonstrate the effect of hedgehog signalling inhibition on aggressive fibromatosis tumour development and β-catenin modulation. We found that hedgehog inhibition decreased cell viability and proliferation as well as total β-catenin levels in human aggressive fibromatosis tumour cells in vitro. Furthermore, following hedgehog inhibition in Apc+/Apc1638N aggressive fibromatosis mouse model, the number and volume of the tumours formed was reduced. Together, this work suggests that hedgehog signalling inhibitor agents are potential candidates to effectively manage aggressive fibromatosis.

Hedgehog (Hh) signalling from the notochord induces the slow muscle cell fate in the adaxial cells of the developing zebrafish embryo. Slow muscle formation is disrupted in zebrafish ??you-type?? mutants resulting in U-shaped somites. In many you-type mutants, genes encoding components of the Hh signalling pathway are mutated. scube2, a gene not previously known to be involved in Hh signalling, is disrupted in the you-type mutant ??you??. you mutants are deficient in several Hh dependent cell types and show decreased expression of Hh target genes. The Scube (signal peptide-CUB domain-EGF-related) family of proteins act as secreted glycoproteins or cell-surface proteins and are thought to be involved in protein-protein interactions and ligand binding. At the protein level, the Scube family resembles the endocytic receptor Cubilin. Cubilin is known to interact with another endocytic receptor Megalin, which can function as an endocytic receptor for Sonic Hedgehog (SHH) in vitro. Megalin endocytosis of Shh may be an important part of the Hh signal transduction pathway. An anti-Scube2 antibody was developed during this work to investigate the intracellular localization pattern of Scube2 and facilitate the identification of potential Scube2 binding partner(s). In addition, this work identified and characterized two homologs of scube2 in zebrafish, scube 1 and scube 3. The high level of similarity amongst the Scube family of proteins and the weak phenotype of the you mutant suggested scube1 and scube3 might also be involved in slow muscle development. Loss of function experiments performed by antisense morpholino knockdown of scube1 and scube3 in the you mutant decreases the expression of Hh target genes to levels seen in embryos lacking Hh signalling and dramatically enhances the loss of slow muscle fibres compared to you mutants alone. Thus, injecting both scube1 and scube3 morpholinos into you blocks Hh signalling and these embryos fail to develop slow muscle. Inhibition of the three partially redundant scube genes inhibits Hh signalling in zebrafish embryos, thereby demonstrating the essential requirement for scube gene function in the Hh signalling pathway.

Hedgehog (Hh) signalling from the notochord induces the slow muscle cell fate in the adaxial cells of the developing zebrafish embryo. Slow muscle formation is disrupted in zebrafish ??you-type?? mutants resulting in U-shaped somites. In many you-type mutants, genes encoding components of the Hh signalling pathway are mutated. scube2, a gene not previously known to be involved in Hh signalling, is disrupted in the you-type mutant ??you??. you mutants are deficient in several Hh dependent cell types and show decreased expression of Hh target genes. The Scube (signal peptide-CUB domain-EGF-related) family of proteins act as secreted glycoproteins or cell-surface proteins and are thought to be involved in protein-protein interactions and ligand binding. At the protein level, the Scube family resembles the endocytic receptor Cubilin. Cubilin is known to interact with another endocytic receptor Megalin, which can function as an endocytic receptor for Sonic Hedgehog (SHH) in vitro. Megalin endocytosis of Shh may be an important part of the Hh signal transduction pathway. An anti-Scube2 antibody was developed during this work to investigate the intracellular localization pattern of Scube2 and facilitate the identification of potential Scube2 binding partner(s). In addition, this work identified and characterized two homologs of scube2 in zebrafish, scube 1 and scube 3. The high level of similarity amongst the Scube family of proteins and the weak phenotype of the you mutant suggested scube1 and scube3 might also be involved in slow muscle development. Loss of function experiments performed by antisense morpholino knockdown of scube1 and scube3 in the you mutant decreases the expression of Hh target genes to levels seen in embryos lacking Hh signalling and dramatically enhances the loss of slow muscle fibres compared to you mutants alone. Thus, injecting both scube1 and scube3 morpholinos into you blocks Hh signalling and these embryos fail to develop slow muscle. Inhibition of the three partially redundant scube genes inhibits Hh signalling in zebrafish embryos, thereby demonstrating the essential requirement for scube gene function in the Hh signalling pathway.

No description available.

The Hedgehog signalling pathway is an essential developmental pathway present in all bilaterians that is involved in embryogenesis, body patterning and stem cell homeostasis. Dysregulation of the Hh pathway leads to various kinds of cancer, such as basal cell carcinoma and medulloblastoma. Smoothened (SMO), a Frizzled-type G-protein coupled receptor (GPCR), is the essential transmembrane signal transducer within the Hh pathway, conveying the signal from the upstream transmembrane protein, Patched1 (Ptc1), to the downstream intracellular proteins. The mechanisms by which SMO transmits the Hh signal from the extracellular environment, through the plasma membrane and to the intracellular proteins are not known. In this thesis, I present my work into the structural and functional characterisation of the extracellular and transmembrane domains (TMD) of human SMO in order to better understand the molecular mechanisms of its signal transduction. The extracellular region of SMO contains a highly conserved cysteine-rich domain (CRD) and a linker domain (LD). I present the first crystal structure of the CRD, LD and TMD of SMO, which is also the first crystal structure of a GPCR with a large functional extracellular domain. This structure revealed a domain architecture for SMO that enables regulation of its transmembrane domain by its extracellular domains. It also revealed a cholesterol molecule bound to the CRD, which we subsequently determined to be a new endogenous small-molecule agonist for SMO. I present five further structures of SMO bound to different small molecule agonists and antagonists. Together, these structures demonstrate that the position of the CRD relative to the TMD reflects the activation state of SMO. We also generated nanobodies against the extracellular region of SMO in order to stabilise its conformation. These studies not only improve our understanding of the workings of a key transmembrane protein within a fundamental signalling pathway but will also aid efforts to develop better therapeutics for an important cancer target.

<p>The generation of hematopoietic progenitors from human pluripotent cell sources for use in personalized medicine is an attainable goal for the ease of clinical intervention using these cells. Furthermore, generated platelets and mature red blood cells are enucleated which allows for the use of induced pluripotent stem cells as a starting source or other sources of genetic manipulation. Generating these cells has proven difficult as the cells appear to be stuck in a primitive state of differentiation and do not mature into an adult phenotype. This thesis shows that inhibition of the hedgehog signaling pathway early in the differentiation of pluripotent stem cells induces a maturation towards definitive hematopoiesis. Generated erythroid cells were shown to express beta globin at the transcript as well as protein level. This maturation effect was confirmed to occur through central hedgehog repressor, Gli3R, through genetic manipulation. Further interrogation of this mechanism showed that globin regulation was not mediated by chromatin methylation by the polycomb repressive complex. Finally, Gli3R was also shown to not act as a transcription factor influencing globin expression directly and is therefore engaging separate regulatory mechanisms. This data provides great strides towards the generation of clinically relevant hematopoietic populations from pluripotent sources, however Gli3R’s direct mechanism of action remains to be determined.</p> / Master of Science (MSc)

Introduction. The inflammatory bowel diseases (IBD), Crohn’s disease (CD) and ulcerative colitis (UC), are common in Western Europe (200-400 cases /100,000) and associated with substantial morbidity, although mortality is now low. There is presently a great unmet need for novel therapeutics in IBD as present agents are limited by lack of efficacy, toxicity and poor patient acceptance. Recent findings from genome-wide association studies (GWAS) have characterised the genetic architecture of CD and UC. Defects in innate and adaptive immunity have been clearly established, and substantial novel insights into disease pathogenesis have been gained. Over 30 genes / loci are now associated with CD; a number of these, along with a few specific loci, are also associated with UC. The hedgehog (HH) signalling pathway is critical to gastrointestinal development and plays key roles in intestinal and immune homeostasis. Furthermore, in addition to well described roles in tumorigenesis, it is evident that recapitulation of embryonic HH signals play critical roles in response to acute and chronic inflammatory challenge in diverse tissues. Aims. The main aims of the work presented in this thesis were to characterise the expression of key HH signalling components in the healthy and inflamed human intestine, establish whether germline variation in HH genes is associated with IBD and describe the in vitro responses of intestinal epithelial cells to pathogen associated molecular patterns. The WNT pathway, antagonised by HH in the intestine, and two HH target genes (NKX2.3 and CCL20) were also analysed for evidence of association with IBD. Methods. Expression of HH and WNT signalling components was described by immunohistochemistry and microarray analysis in healthy controls (HC), CD, UC, and non- IBD inflamed terminal ileal and colonic samples. Gene-wide haplotype-tagging studies were performed for GLI1 in Scottish, English and Swedish CD and UC, and Scottish early-onset colo-rectal cancer, IHH in Scottish IBD, NKX2.3 in Scottish and UK IBD, and CCL20 in Scottish, Swedish and Japanese IBD. Evidence for association of all HH (n=13) and WNT (n=27) signalling genes in CD was established by analysis of UK GWAS data and metaanalysis from UK, French/Belgium and N American studies. The effect of lipopolysaccharide (LPS) and muramyl dipeptide (MDP) on HH signalling was assessed in colonic epithelial cells (SW480). The effect of HH pathway agonists and antagonists on NFκB activity and cytokine expression was analysed in SW480 cells and peripheral blood mononuclear cells (HC and IBD patients) in vitro. Results. The expression of HH pathway ligand is present in the intestinal epithelium and the pathway response network in the lamina propria demonstrating the paracrine nature of HH signalling in the intestine. Immunohistochemical studies and microarray analysis demonstrates that HH pathway activity is decreased in all forms of colonic inflammation studied in man. Variation in Glioma-associated oncogene homolog 1 (GLI1), a key HH transcription factor located at 12q13 (IBD2), was associated with IBD (p<0.0001), UC (p<0.0001) and to a lesser extent CD (p=0.03) in Scotland, a finding replicated in English IBD and UC. This association was attributed to a non-synonymous SNP (rs2228226C→G) with pools odds ratio of 1.194 in meta-analysis of over 5000 individuals from Scotland, England and Sweden (p=0.0002). There was association of this SNP with early-onset colorectal cancer, but of borderline significance (p=0.05). The variant protein (Q1100E) is 50% less active than wild-type protein in vitro. IHH was not associated with CD or UC. Preliminary evidence was produced for association at SUFU (10q24; p=0.005), a GLI1- binding protein, and at the WNT3 / WNT9B locus (17q21; p=0.0005). MDP stimulation of colonic epithelial cells decreased HH pathway activity. Exogenous HH increased expression of CCL20. CCL20 promoter polymorphisms were associated with UC in Japanese patients (p=0.018) but not in Scotland or Sweden. NKX2.3 was associated with IBD in Scotland (UC>CD), but there was insufficient power for fine-mapping of causative variants. Conclusions. Multiple lines of evidence presented here demonstrate that the HH signalling pathway is involved in IBD pathogenesis. In key complementary in vivo studies (conceived by CWL; conducted in collaboration with the Gumucio lab in Ann Arbor) we have demonstrated that Gli1+/- mice develop early, severe colitis with high mortality in response to acute inflammatory challenge. Furthermore, lamina propria antigen presenting cells are identified as the key HH target cells. With HH agonists and antagonists in extensive preclinical and early clinical testing, these studies have real potential to translate into novel therapeutics for patients with IBD.