Role of TrkB in neonatal ovary development

The signalling cascade induced by the binding of neurotrophins (NGF, BDNF, NT3 and NT4) to their high-affinity tyrosine kinase receptors (TrkA, B and C) is well documented to be important for neuronal cell survival, proliferation and differentiation. Evidence has accumulated demonstrating the importance of these signalling pathways in nonneuronal tissues, including the ovary where all neurotrophins and their receptors are expressed. In the mouse, effects on ovulation have been demonstrated but the role of Trk signalling in neonatal ovary development is less clear. Previous work had found that TrkB expression is upregulated at the time of follicle formation in the mouse and transgenic mice null for the TrkB receptor demonstrate significant loss of oocytes neonatally (TrkB knockouts, KO, die shortly after birth). This thesis examines the phenotype of the TrkB KO using morphological, histological and surgical techniques with the aim being to further investigate the role of TrkB signalling in oocyte survival, and to contribute to our understanding of neonatal ovary development. The main questions addressed are: 1) what developmental defects are occurring on a morphological level that result in the phenotype of the TrkB KO; 2) can these defects be quantified; and 3) what are the longterm survival prospects for TrkB KO oocytes. Morphological assessment revealed that TrkB KO ovaries exhibit poorer follicle health than their Controls and this was confirmed by assessment of basement membrane (BM) composition. TrkB KO brain and kidney were also assessed and found to have similarly affected BM. It is well known that cells require contact with the BM to maintain survival, thus it is postulated that TrkB signalling contributes to oocyte survival through regulation of the BM. Due to the postnatal lethality of the mutation, TrkB KO ovaries were transplanted to ascertain long-term oocyte survival. Unexpectedly it was found that TrkB KO oocytes are able to survive and follicles grow as well as they do in the Control transplants. Consequently, the in vivo effect has to be indirect. It is known that oocytes in the neonatal ovary undergo an increased rate of cell death but it is not known how the cell debris is removed. A novel observation of a neonatal ovarian immune response has been made in this thesis and is postulated to be a physiological mechanism for cell debris clearance. In conclusion, this thesis has demonstrated that signalling through TrkB has an effect on regulating BM in the ovary and other organs, but that surprisingly it has an indirect effect on oocyte survival

Prokineticin 1 induces a pro-inflammatory response in murine fetal membranes but does not induce preterm delivery

The mechanisms that regulate the induction of term or preterm delivery (PTD) are not fully understood. Infection is known to play a role in the induction of pro-inflammatory cascades in uteroplacental tissues associated with preterm pathological parturition. Similar but not identical cascades are evident in term labour. In the current study, we used a mouse model to evaluate the role of prokineticins in term and preterm parturition. Prokineticins are multi-functioning secreted proteins that signal through G-protein-coupled receptors to induce gene expression, including genes important in inflammatory responses. Expression of prokineticins (Prok1 and Prok2) was quantified in murine uteroplacental tissues by QPCR in the days preceding labour (days 16-19). Prok1 mRNA expression increased significantly on D18 in fetal membranes (compared with D16) but not in uterus or placenta. Intrauterine injection of PROK1 on D17 induced fetal membrane mRNA expression of the pro-inflammatory mediators Il6, Il1b, Tnf, Cxcl2 and Cxcl5, which are not normally up-regulated until D19 of pregnancy. However, intrauterine injection of PROK1 did not result in PTD. As expected, injection of lipopolysaccharide (LPS) induced PTD, but this was not associated with changes in expression of Prok1 or its receptor (Prokr1) in fetal membranes. These results suggest that although Prok1 exhibits dynamic mRNA regulation in fetal membranes preceding labour and induces a pro-inflammatory response when injected into the uterus on D17, it is insufficient to induce PTD. Additionally, prokineticin up-regulation appears not to be part of the LPS-induced inflammatory response in mouse fetal membranes.Tamsin R M Lannagan, Martin R Wilson, Fiona Denison, Jane E Norman, Rob D Catalano and Henry N Jabbou

Pathway level subtyping identifies a slow-cycling biological phenotype associated with poor clinical outcomes in colorectal cancer

Molecular stratification using gene-level transcriptional data has identified subtypes with distinctive genotypic and phenotypic traits, as exemplified by the consensus molecular subtypes (CMS) in colorectal cancer (CRC). Here, rather than gene-level data, we make use of gene ontology and biological activation state information for initial molecular class discovery. In doing so, we defined three pathway-derived subtypes (PDS) in CRC: PDS1 tumors, which are canonical/LGR5+ stem-rich, highly proliferative and display good prognosis; PDS2 tumors, which are regenerative/ANXA1+ stem-rich, with elevated stromal and immune tumor microenvironmental lineages; and PDS3 tumors, which represent a previously overlooked slow-cycling subset of tumors within CMS2 with reduced stem populations and increased differentiated lineages, particularly enterocytes and enteroendocrine cells, yet display the worst prognosis in locally advanced disease. These PDS3 phenotypic traits are evident across numerous bulk and single-cell datasets, and demark a series of subtle biological states that are currently under-represented in pre-clinical models and are not identified using existing subtyping classifiers

Role of TrkB in neonatal ovary development

The signalling cascade induced by the binding of neurotrophins (NGF, BDNF, NT3 and NT4) to their high-affinity tyrosine kinase receptors (TrkA, B and C) is well documented to be important for neuronal cell survival, proliferation and differentiation. Evidence has accumulated demonstrating the importance of these signalling pathways in nonneuronal tissues, including the ovary where all neurotrophins and their receptors are expressed. In the mouse, effects on ovulation have been demonstrated but the role of Trk signalling in neonatal ovary development is less clear. Previous work had found that TrkB expression is upregulated at the time of follicle formation in the mouse and transgenic mice null for the TrkB receptor demonstrate significant loss of oocytes neonatally (TrkB knockouts, KO, die shortly after birth). This thesis examines the phenotype of the TrkB KO using morphological, histological and surgical techniques with the aim being to further investigate the role of TrkB signalling in oocyte survival, and to contribute to our understanding of neonatal ovary development. The main questions addressed are: 1) what developmental defects are occurring on a morphological level that result in the phenotype of the TrkB KO; 2) can these defects be quantified; and 3) what are the longterm survival prospects for TrkB KO oocytes. Morphological assessment revealed that TrkB KO ovaries exhibit poorer follicle health than their Controls and this was confirmed by assessment of basement membrane (BM) composition. TrkB KO brain and kidney were also assessed and found to have similarly affected BM. It is well known that cells require contact with the BM to maintain survival, thus it is postulated that TrkB signalling contributes to oocyte survival through regulation of the BM. Due to the postnatal lethality of the mutation, TrkB KO ovaries were transplanted to ascertain long-term oocyte survival. Unexpectedly it was found that TrkB KO oocytes are able to survive and follicles grow as well as they do in the Control transplants. Consequently, the in vivo effect has to be indirect. It is known that oocytes in the neonatal ovary undergo an increased rate of cell death but it is not known how the cell debris is removed. A novel observation of a neonatal ovarian immune response has been made in this thesis and is postulated to be a physiological mechanism for cell debris clearance. In conclusion, this thesis has demonstrated that signalling through TrkB has an effect on regulating BM in the ovary and other organs, but that surprisingly it has an indirect effect on oocyte survival.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Role of TrkB in neonatal ovary development

The signalling cascade induced by the binding of neurotrophins (NGF, BDNF, NT3 and NT4) to their high-affinity tyrosine kinase receptors (TrkA, B and C) is well documented to be important for neuronal cell survival, proliferation and differentiation. Evidence has accumulated demonstrating the importance of these signalling pathways in nonneuronal tissues, including the ovary where all neurotrophins and their receptors are expressed. In the mouse, effects on ovulation have been demonstrated but the role of Trk signalling in neonatal ovary development is less clear. Previous work had found that TrkB expression is upregulated at the time of follicle formation in the mouse and transgenic mice null for the TrkB receptor demonstrate significant loss of oocytes neonatally (TrkB knockouts, KO, die shortly after birth). This thesis examines the phenotype of the TrkB KO using morphological, histological and surgical techniques with the aim being to further investigate the role of TrkB signalling in oocyte survival, and to contribute to our understanding of neonatal ovary development. The main questions addressed are: 1) what developmental defects are occurring on a morphological level that result in the phenotype of the TrkB KO; 2) can these defects be quantified; and 3) what are the longterm survival prospects for TrkB KO oocytes. Morphological assessment revealed that TrkB KO ovaries exhibit poorer follicle health than their Controls and this was confirmed by assessment of basement membrane (BM) composition. TrkB KO brain and kidney were also assessed and found to have similarly affected BM. It is well known that cells require contact with the BM to maintain survival, thus it is postulated that TrkB signalling contributes to oocyte survival through regulation of the BM. Due to the postnatal lethality of the mutation, TrkB KO ovaries were transplanted to ascertain long-term oocyte survival. Unexpectedly it was found that TrkB KO oocytes are able to survive and follicles grow as well as they do in the Control transplants. Consequently, the in vivo effect has to be indirect. It is known that oocytes in the neonatal ovary undergo an increased rate of cell death but it is not known how the cell debris is removed. A novel observation of a neonatal ovarian immune response has been made in this thesis and is postulated to be a physiological mechanism for cell debris clearance. In conclusion, this thesis has demonstrated that signalling through TrkB has an effect on regulating BM in the ovary and other organs, but that surprisingly it has an indirect effect on oocyte survival.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

BCL-XL is crucial for progression through the adenoma-to-carcinoma sequence of colorectal cancer

Evasion of apoptosis is a hallmark of cancer, which is frequently mediated by upregulation of the antiapoptotic BCL-2 family proteins. In colorectal cancer (CRC), previous work has highlighted differential antiapoptotic protein dependencies determined by the stage of the disease. While intestinal stem cells (ISCs) require BCL-2 for adenoma outgrowth and survival during transformation, ISC-specific MCL1 deletion results in disturbed intestinal homeostasis, eventually contributing to tumorigenesis. Colon cancer stem cells (CSCs), however, no longer require BCL-2 and depend mainly on BCL-XL for their survival. We therefore hypothesized that a shift in antiapoptotic protein reliance occurs in ISCs as the disease progresses from normal to adenoma to carcinoma. By targeting antiapoptotic proteins with specific BH3 mimetics in organoid models of CRC progression, we found that BCL-2 is essential only during ISC transformation while MCL1 inhibition did not affect adenoma outgrowth. BCL-XL, on the other hand, was crucial for stem cell survival throughout the adenoma-to-carcinoma sequence. Furthermore, we identified that the limited window of BCL-2 reliance is a result of its downregulation by miR-17-5p, a microRNA that is upregulated upon APC-mutation driven transformation. Here we show that BCL-XL inhibition effectively impairs adenoma outgrowth in vivo and enhances the efficacy of chemotherapy. In line with this dependency, expression of BCL-XL, but not BCL-2 or MCL1, directly correlated to the outcome of chemotherapy-treated CRC patients. Our results provide insights to enable the rational use of BH3 mimetics in CRC management, particularly underlining the therapeutic potential of BCL-XL targeting mimetics in both early and late-stage disease

Loss of Grem1-lineage chondrogenic progenitor cells causes osteoarthritis

Abstract Osteoarthritis (OA) is characterised by an irreversible degeneration of articular cartilage. Here we show that the BMP-antagonist Gremlin 1 (Grem1) marks a bipotent chondrogenic and osteogenic progenitor cell population within the articular surface. Notably, these progenitors are depleted by injury-induced OA and increasing age. OA is also caused by ablation of Grem1 cells in mice. Transcriptomic and functional analysis in mice found that articular surface Grem1-lineage cells are dependent on Foxo1 and ablation of Foxo1 in Grem1-lineage cells caused OA. FGFR3 signalling was confirmed as a promising therapeutic pathway by administration of pathway activator, FGF18, resulting in Grem1-lineage chondrocyte progenitor cell proliferation, increased cartilage thickness and reduced OA. These findings suggest that OA, in part, is caused by mechanical, developmental or age-related attrition of Grem1 expressing articular cartilage progenitor cells. These cells, and the FGFR3 signalling pathway that sustains them, may be effective future targets for biological management of OA

MmCMS: mouse models’ consensus molecular subtypes of colorectal cancer

BackgroundColorectal cancer (CRC) primary tumours are molecularly classified into four consensus molecular subtypes (CMS1–4). Genetically engineered mouse models aim to faithfully mimic the complexity of human cancers and, when appropriately aligned, represent ideal pre-clinical systems to test new drug treatments. Despite its importance, dual-species classification has been limited by the lack of a reliable approach. Here we utilise, develop and test a set of options for human-to-mouse CMS classifications of CRC tissue.MethodsUsing transcriptional data from established collections of CRC tumours, including human (TCGA cohort; n = 577) and mouse (n = 57 across n = 8 genotypes) tumours with combinations of random forest and nearest template prediction algorithms, alongside gene ontology collections, we comprehensively assess the performance of a suite of new dual-species classifiers.ResultsWe developed three approaches: MmCMS-A; a gene-level classifier, MmCMS-B; an ontology-level approach and MmCMS-C; a combined pathway system encompassing multiple biological and histological signalling cascades. Although all options could identify tumours associated with stromal-rich CMS4-like biology, MmCMS-A was unable to accurately classify the biology underpinning epithelial-like subtypes (CMS2/3) in mouse tumours.ConclusionsWhen applying human-based transcriptional classifiers to mouse tumour data, a pathway-level classifier, rather than an individual gene-level system, is optimal. Our R package enables researchers to select suitable mouse models of human CRC subtype for their experimental testing.<br/