Chloride intracellular channels (CLICs), 1 and 4 are expressed in endothelial cells where they promote cell proliferation, migration and vessel morphogenesis in vitro. Clic4-/- mice exhibit defects in retinal angiogenesis suggesting CLIC4 functions as an angiogenic regulator. S1P signaling, through S1P receptors S1P1 and S1P2, is essential for endothelial cell functions during vascular development. S1P treatment promotes CLIC4 localization to cell surface suggesting a link between CLICs and S1P pathways. Here we demonstrate that CLICs function in embryonic development, retinal angiogenesis and vascular permeability regulation. Clic1-/-;Clic4-/- embryos die in utero and exhibit severe growth restriction with vascular defects prior to death. Loss of Clic4 in murine endothelium (Clic4ECKO) caused aberrant retinal angiogenesis characterized by reduced vascular outgrowth and increased vessel sprouting. Clic4ECKO mice exhibited increased vessel leakiness as assessed by a lung permeability assay. We establish that CLIC1 and CLIC4 function in distinct branches of the S1P pathway to promote angiogenesis. Knockdown of CLIC1 or CLIC4 in endothelial cells impeded S1P1-mediated induction of AKT and Rac1 and reduced endothelial cell migration and adherence junctions formation. CLIC1 knockdown alone inhibited RhoA activation and actin stress fibers downstream of S1P2. Using pharmacological perturbation of S1P signaling in Clic knockout mice we established that Clic4 is essential for S1P1-mediated regulation of retinal angiogenesis and vascular permeability. We conclude that CLIC1 and CLIC4 function as effectors in the S1P pathway, where they have overlapping functions in S1P1-PI3K signaling and CLIC1 uniquely acts as an effector in S1P2-RhoA signaling cascade. Through these findings, our work defines a molecular mechanism through which CLICs function in endothelium.

A major pursuit of Developmental Biology is to determine how organisms composed of cells containing a single genome generate stereotyped body plans with diverse, complex morphologies. The development of these patterns is often determined by gradients of secreted factors known as morphogens, which activate cascades of gene expression to subdivide fields of cells into increasingly complex patterns. In many animals, including Drosophila, a rudimentary anterior-posterior (A-P) and dorsal-ventral (D-V) axes of the body plan are already established in the zygote, but the proximal-distal (P-D) axis of any appendages must be generated and patterned seperately. The spatio-temporal information responsible for activating gene expression and cell signalling that establishes this new axis is integrated at DNA regulatory elements often referred to as enhancers. The segmented leg of the insect Drosophila melanogaster offers an ideal system for studying how signalling pathways control P-D axis establishment and patterning. In addition to the fact that flies are a particularly genetically tractable model organism, many of the signals required for leg patterning have already been identified. A number of signalling pathways, including Wingless (Wg), Decapentaplegic (Dpp) and Epidermal Growth Factor Receptor (EGFR), are important for proper P-D axis patterning in a dynamic fashion during embryonic and larval development. The leg primordia are fist specified in the embryo and then patterned throughout development as intercalated circles and rings of gene expression are established in the leg imaginal disc. The radius of these domains corresponds to the P-D axis of the adult appendage. A rudimentary P-D axis is established in the embryo and the larval leg imaginal disc by the expression of the transcription factors Distalless, Dachshund and Homothorax in distal, medial and proximal domains, respectively. The P-D axis is further refined by activation of EGFR signalling in the presumptive tarsus, the distal-most portion of the fly leg, during the early third larval instar. As well as slightly later, in medial and proximal rings. EGFR signalling is a ubiquitous pathway with numerous roles throughout fly development as well as across metazoan taxa. Its activation produces diverse cellular outcomes such as growth, differentiation, or regulation of apoptosis depending on the precise regulation of its inputs and modulation of intracellular signalling components in a tissue-specific manner. The precise mechanism by which EGFR signalling is activated during tarsal patterning is the focus of this dissertation. As a crucial first step in the detailed characterization of EGFR activation in the leg, we have identified leg-specific enhancers of the genes encoding the neuregulin-like EGF ligand Vein and the ligand-activating protease Rhomboid and performed genetic and site-specific mutagenesis experiments to characterize the factors necessary to activate expression of vein and rho in the distal leg. While the enhancers of vein and rho (vnE and rhoE, respectively) employ similar transcriptional programs to activate target gene expression, there are some key differences. Both enhancers require Dll for their expression throughout leg development, however vnE requires Wg and Dpp only early and later becomes independent from these signals while rhoE requires them until much later in development. Further, vnE requires Sp1 while rhoE does not. These differences may be important for the precise timing of expression of these genes, with vn expression coming on several hours earlier than that of rho. It has been proposed that the distal source of EGFR ligand may act as a long-range morphogen to pattern the entire tarsus in a graded manner (Campbell, 2002; Galindo et al., 2005). Our analysis indicates that vnE and rhoE represent the only sources of EGFR ligand in the distal leg. Therefore, in order to determine the importance of distal of EGFR signalling for tarsal patterning we carried out CRISPR targeting to delete vnE and rhoE. Because these deletions produce only mild distal leg truncations and cannot be worsened by removal of other candidate EGFR inputs (for example the Rho homolog, Roughoid) we conclude that the long-range distal gradient model for P-D patterning by EGFR must be revised. Instead we propose that the tarsal segments are patterned by the combined action of a local, distal gradient of EGFR supplied by vnE and rhoE combined with secondary, more medial sources of EGFR signal. Our analysis of the mechanism by which EGFR patterns the distal leg segments improves our understanding not only of leg development, but also of how the EGFR pathway is regulated in general. Our conclusions have important evolutionary implications, as receptor tyrosine kinase signalling, of which EGFR is an example, is involved in limb patterning in taxa whose limbs themselves are not thought to be structurally homologous to fly legs (Panganiban et al., 1997; Pires-daSilva and Sommer, 2003). Further, the components of the EGFR pathway assessed in this work are highly conserved signalling molecules, involved in cell proliferation and are therefore often misregulated in tumors. A nuanced understanding of the ways in which EGFR signalling is activated, particularly via regulation at non-protein-coding loci, could motivate new therapeutic approaches.

Yeung Lam. / Thesis submitted in: December 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 134-150). / Abstracts in English and Chinese. / ABSTRACT --- p.I / 摘要 --- p.III / ACKNOWLEDGMENT --- p.V / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- General review of angiogenesis --- p.1 / Chapter 1.2 --- Vascular endothelial growth factors (VEGFs) --- p.2 / Chapter 1.2.1 --- VEGF-A --- p.2 / Chapter 1.2.2 --- P1GF --- p.4 / Chapter 1.2.3 --- VEGF-B --- p.5 / Chapter 1.2.4 --- VEGF-C and VEGF-D --- p.6 / Chapter 1.3 --- VEGF receptors (VEGFRs) --- p.9 / Chapter 1.3.1 --- VEGFR-1 (or flt-1) --- p.9 / Chapter 1.3.2 --- VEGFR-2 ( or flk-1) --- p.10 / Chapter 1.3.3 --- VEGFR-3 ( or flt-4) --- p.11 / Chapter 1.4 --- Hormonal regulation of VEGFs by LH/hCG --- p.14 / Chapter 1.5 --- General review of the testis --- p.17 / Chapter 1.5.1 --- Structure and function of the testis --- p.17 / Chapter 1.5.2 --- Testicular vasculature --- p.18 / Chapter 1.5.3 --- Testicular angiogenesis --- p.19 / Chapter 1.6 --- Localization of VEGF and VEGF receptors in the testis --- p.20 / Chapter 1.7 --- Aims of the present study --- p.21 / Chapter 2. --- Materials and methods --- p.23 / Chapter 2.1 --- Animals --- p.23 / Chapter 2.1.1 --- Depletion of Leydig cell --- p.23 / Chapter 2.1.2 --- Suppression of Leydig cell and stimulation by hCG --- p.24 / Chapter 2.1.3 --- Collection of tissue --- p.25 / Chapter 2.2 --- Preparation of primary cells from rat testes --- p.27 / Chapter 2.2.1 --- Sertoli cell preparation --- p.27 / Chapter 2.2.2 --- Germ cell preparation --- p.29 / Chapter 2.2.3 --- Interstitial cell and Leydig cell preparation --- p.30 / Chapter 2.3 --- Cell cultures --- p.32 / Chapter 2.3.1 --- Reagents and cell lines --- p.32 / Chapter 2.3.2 --- "Mouse Leydig cell line, TM3 and Sertoli cell line, TM4" --- p.33 / Chapter 2.3.3 --- "Mouse tumor Leydig cell line, MLTC-1" --- p.34 / Chapter 2.3.4 --- "Rat tumor Leydig cell line, R2C" --- p.34 / Chapter 2.3.5 --- "Rat tumor Leydig cell line, LC540" --- p.35 / Chapter 2.4 --- Reverse-transcription polymerase chain reaction (RT-PCR) and semi-quantitative RT-PCR --- p.35 / Chapter 2.4.1 --- Extraction of total RNA --- p.35 / Chapter 2.4.2 --- Quantitation of total RNA --- p.37 / Chapter 2.4.3 --- RT-PCR --- p.37 / Chapter 2.4.4 --- Purification and authentication of PCR products --- p.47 / Chapter 2.5 --- Immunohistochemical staining --- p.48 / Chapter 2.5.1 --- Perfusion and processing of testes for histological sections --- p.48 / Chapter 2.5.2 --- Immunohistochemical staining of tissue sections --- p.50 / Chapter 2.6 --- Western immunoblotting --- p.52 / Chapter 2.6.1 --- Extraction and quantitation of total protein --- p.52 / Chapter 2.6.2 --- SDS-PAGE --- p.53 / Chapter 2.6.3 --- Immunoblotting --- p.55 / Chapter 2.7 --- Statistical analyses --- p.57 / Chapter 3. --- Results --- p.58 / Chapter 3.1 --- Expression and localization of VEGFs in the rat testis --- p.58 / Chapter 3.1.1 --- VEGF-A --- p.58 / Chapter 3.1.2 --- VEGF-B --- p.64 / Chapter 3.1.3 --- VEGF-C --- p.69 / Chapter 3.1.4 --- VEGF-D --- p.73 / Chapter 3.1.5 --- P1GF --- p.77 / Chapter 3.2 --- Effect of Leydig cell depletion on VEGFs expression in the rat testis --- p.81 / Chapter 3.2.1 --- Effect on VEGF-A --- p.81 / Chapter 3.2.2 --- Effect on VEGF-B --- p.82 / Chapter 3.2.3 --- Effect on VEGF-C --- p.88 / Chapter 3.2.4 --- Effect on VEGF-D --- p.91 / Chapter 3.2.5 --- Effect on P1GF --- p.94 / Chapter 3.3 --- Effect of Leydig cell suppression and hCG stimulation on VEGFs expression in the rat testis --- p.97 / Chapter 3.3.1 --- Effect on VEGF-A --- p.97 / Chapter 3.3.2 --- Effect on VEGF-B --- p.107 / Chapter 3.3.3 --- Effect on VEGF-C --- p.113 / Chapter 3.3.4 --- Effect on VEGF-D --- p.119 / Chapter 4. --- Discussion --- p.126 / Chapter 5. --- References --- p.134

No description available.

The widespread expression of polypeptide growth factors from the earliest stages of embryonic development through to mature issues in the adult organism suggests an involvement in a reiterated developmental process affecting the underlying cellular growth and differentiation of many tissues. The hair follicle has taken on increased significance with the observation that many genetic mutations in these peptide growth factor genes affect its development. The targeted disruption of genes encoding members of the EpidermalGrowth Factor (EGF) and Fibroblast Growth Factor (FGF) families in the mouse has revealed a functional role for these proteins in the regulation of hair follicle growth. Experimental data and other factors are examined and results given. A second experimental system was used to determine if a functional relationship between certain peptide growth factors was conserved in the Merino sheep. The induction of a catagen-like state in the wool follicle and other epidermal changes associated with EGF treatment may be related to the transciptional induction of these peptide growth factors / Doctor of Philosophy (PhD)

The transforming growth factor (TGF)-β superfamily mediates a wide range of differentiation and developmental processes across many genera. GDF9 and BMP15 are expressed exclusively in the mammalian ovary and are the only TGF-β ligands that lack the conserved cysteine residue used for dimerisation. As a platform for studying the interactions between GDF9 and BMP15 and their receptors, BMPRII and BMPRIb, a variety of strategies were attempted to produce soluble and active proteins from recombinant systems. Both ligands and receptors showed a tendency to form insoluble aggregates when expressed in prokaryotic systems; however after extensive screening, quantities of biologically active GDF9 were produced using in vitro refolding. When expressed alone, either containing a histidine tag or as an untagged protein, the BMPRII ectodomain was deposited as insoluble inclusion bodies. This protein, subjected to in vitro refolding procedures, exhibited multiple species following anion exchange chromatography and size exclusion chromatography, as visualised on native PAGE. Separation of these species could be achieved using a MonoP matrix. One of these separated fractions, representing about 5% of the starting material, was amenable to crystallisation, and furthermore exhibited activity in a rat granulosa cell thymidine incorporation assay. Two different crystals forms of the extracellular domain of BMPRII were grown from the same protein batch under similar crystallisation conditions. Notably, the tetragonal form that grew more slowly possessed several disordered finger regions, while electron density for the entire molecule was clear in the orthorhombic form. The hydrophobic core of the ligand binding surface of BMPRII , as seen in both structures, resembles that of ActRII bound to BMP2. The A-loop of BMPRII, which is involved in ligand binding, lies in two different conformations in the two structures of BMPRII, mediated by a rearrangement in disulfide Cys94-Cys117. It is proposed here that the tetragonal form represents the ligand-bound receptor structure. Although the majority of the hydrophobic binding surface is shared with ActRII(b), it is likely that His87 and Tyr40 are unique residues that confer specificity in BMPRII ligand binding.

The survival of motor neurons is controlled by multiple factors, which regulate different aspects of their physiology. The identification of these factors is important because of their relevance for motor neuron disease. This thesis began with a search for novel growth factors that naturally keep these neurons alive. Members of the TGF-β superfamily, including Mullerian inhibiting substance (MIS) and bone morphogenetic protein 6 (BMP6), were identified as putative survival factors following a cDNA microarray analysis of a mouse model of motor neuron disease. MIS is a gonad-derived hormone with a male bias. It induces the degeneration of the female reproductive tract during development and it was thought to have no physiological function outside of the reproductive system. In this thesis, multiple techniques were used to show that adult motor neurons produce MIS and its receptors. The copy number of MIS mRNA in motor neurons was comparable with that of the testis, whereas the mRNA of the MIS type II receptor (MISRII) in motor neurons appeared to be the most abundant receptor of the TGF-β superfamily. These results were confirmed using Western blot and immunohistochemistry. Thus, MIS may exert its function through an autocrine or a paracrine mechanism between neighbouring motor neurons. The function of MIS was examined using a culture system and a mouse null mutation of MISRII. The in vitro assays showed strong neurotrophic effects of MIS on embryonic motor neurons with the maximum extent of survival being similar to that achieved by the classical motor neuron survival factor, GDNF. MIS has a male bias in utero raising the issue of whether motor neurons are sexually dimorphic. Consistent with this, the number of motor neurons in the lumbar lateral motor column of neonatal male MISRII+/+ mice was 13 % greater than in female mice (P = 0.01). The nuclei of male motor neurons were approximately 20 % larger than their female counterparts (P = 0.000). MISRII-/- male mice had 18 % fewer motor neurons than wild-type males (P = 0.01) and the mean size of their motor neurons was 20 % smaller (P = 0.000). The number and size of motor neurons in the MISRII-/- males was not different to those of MISRII+/+ females. These results implicate MIS as being responsible for neuronal survival as well as producing sexual dimorphism of the limb innervating motor neurons. Since MIS does not appear to be expressed in the embryonic neuromuscular system, it is postulated that MIS is a gonad-derived neurotrophic factor for developing motor neurons. The BMP type II receptor (BMPRII) was the second most abundant receptor of the TGF-β superfamily expressed by motor neurons. One of its ligands, BMP6, was found to have a neurotrophic effect on motor neurons in culture but was slightly less potent than MIS. BMP6 mRNA was detected in nerve, skeletal muscle and spinal cord, but not in motor neurons. BMP6 immunoreactivity was mainly associated with the myelinated Schwann cells and satellite glia that surround motor neurons. In skeletal muscles, immunoreactivity was not detected in muscle fibers, nor the postsynaptic region of the neuromuscular junction (NMJ). BMP6 was, however, associated with the interstitial cells of skeletal muscles. Double nerve ligations were used to examine whether Schwann cell-derived BMP6 interacts with motor neurons. Consistent with this, BMP6 was retrogradely transported in motor axons. These observations collectively suggest that BMP6 is a glia-derived regulator of motor neurons. MIS and minority of BMP6 were anterogradely transported towards the NMJ. Their receptors, MISRII and BMPRII, were detected in the postsynaptic portions of the adult NMJ. These observations raised the possibility that MIS and BMP6 may be regulators of the adult NMJ. Since functional redundancy amongst the members of the TGF-β superfamily has been suggested, the function of MIS/BMP6 signaling at the NMJ was therefore examined in mice with muscle-specific deletion of Smad4, a central mediator of TGF-β superfamily pathways. More than 75% of animals lacking Smad4 in muscles died before embryonic day (E) 14 and none survived postnally. This was due to the loss of functional Smad4 in developing cardiac myocytes, which resulted in severe heart defects and early death of embryos. Thus, the function of MIS/BMP6 signaling at the adult NMJ could not be studied. Finally, this thesis briefly examined the phenotypes of mice carrying double null mutations of MISRII and TGF-β2. The animals died at an early stage and showed a more severe phenotype than either of the single null mutants. This suggests that functional redundancy among members of the TGF-β superfamily exists in many organs. In summary, motor neurons require multiple sources of growth factors for their survival. MIS and BMP6 were discovered as novel survival factors for motor neurons in this study. MIS was implicated as a regulator of sexual dimorphism in developing motor neurons, whereas both MIS and BMP6 appear to regulate mature motor neurons, and possibly the NMJ.

Human granulosa cells play an important role in the follicle, providing the oocyte with nutrients and growth factors to ensure successful ovulation. Normal granulosa cell functioning is thus crucial to human fertility. By studying their transcriptome, the mechanisms underpinning follicle development and infertility will be better understood. In this study, granulosa cells were retrieved at the time of oocyte removal for in vitro fertilization (IVF). Cells were purified through a combination of a Percoll gradient to remove red blood cells and positive selection of granulosa cell aggregations. On average, contamination by white blood cells was 2% as measured by FACS analysis using specific white blood cell markers. Histological and electron microscopy of granulosa cell aggregations did not detect evidence of resident ovarian white blood cells. This technique provided a good source of pure, healthy granulosa cells for RNA extraction and subsequent gene expression studies. The construction of a human granulosa cell SAGE library derived 1689 SAGEtags and 1289 discrete mRNA transcripts. SAGEtags for a number of well recognized granulosa cell genes (FSH receptor, follistatin, connexin 43) were found in addition to hormone receptors, multiple kinases, structural genes, apoptosis related genes and secreted proteins. A variety of other SAGE libraries were downloaded from SAGEmap (two ovary epithelium, ovary, white blood cell, brain, cerebellum, heart, liver, lung, kidney, pancreas and universal human reference) and compared to the human granulosa cell library. This was based on two measures: a gene specificity score (GSS) and a tissue specificity score (TSS). Three SAGEtags were identified with high levels of expression in granulosa cells, but no or low expression in the other libraries. These were retinol binding protein 1 (RBP 1), scavenger receptor class B member 1 (SCARB 1) and hydroxysteroid (11-beta) dehydrogenase 1 (11-β-HSD). Library comparisons were validated by real time RT-PCR. The TSS score revealed granulosa cells were most similar to the universal reference library and least similar to liver. Granulosa cell samples were collected from woman undergoing IVF for a range of infertility disorders. These included polycystic ovary syndrome (PCOS), tubal disease, endometriosis and idiopathic (unknown). Gene expression was compared between these groups using real time RT-PCR. Candidate genes included RBP 1, 11-β-HSD, SCARB 1, FSH receptor, follistatin, decidual protein induced by progesterone, and progesterone membrane receptor component 1 and 2. Granulosa cell gene expression was significantly different (p<0.05) from human white blood cells. No differences were found in gene expression levels between the infertility disorders. Analysis of each patient, however, revealed individuals with marked over-expression of selected genes. The technique of Generation of Longer cDNA fragments for Gene Identification (GLGI) was used to investigate seven SAGEtags that did match known genes or ESTs. Although no novel genes were characterized, a further 14 granulosa cell transcripts were identified by this technique. This thesis used an integrated approach to the study of human granulosa cell gene expression. This has involved development of a purification method, the use of a high-throughput technique (SAGE), bioinformatics tools to identify candidates genes, real time RT-PCR to investigate gene expression of particular genes in infertility disorders and finally a technique with the potential to characterize unknown SAGEtags (GLGI). This systematic approach has advanced the understanding of gene expression in human granulosa cells and identified avenues for future research into folliculogenesis and human infertility.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (M.S.)- -University of Puerto Rico, Mayagüez Campus, 2005. / Tables. Printout. Includes bibliographical references (leave 72)