Xian-Jie Yang - US grants

DESCRIPTION (provided by applicant): The long-term goal of this research is to elucidate mechanisms by which cell-extrinsic signals influence progenitor cell fate specification and neuronal differentiation. The proposed study focuses on mechanisms by which ciliary neurotrophic factor (CNTF)-like cytokines act in the mouse retina. During development, CNTF affects the differentiation of photoreceptor cells, bipolar cells, and Muller glia; while in the mature retina, CNTF enhances retinal ganglion cell survival and prevents photoreceptor degeneration in various mammalian models. We have demonstrated that CNTF differentially activates intracellular signaling pathways in proliferating progenitors and postmitotic neurons in the neonatal retina; CNTF-dependent inhibition of rod photoreceptor differentiation requires STAT function, whereas CNTF-enhanced production of Muller glia involves both STAT and ERK activities. We hypothesize that STAT and ERK signaling play distinct roles in retinal progenitor cells and in postmitotic cells. To test this hypothesis, we will perturb cytokine signaling pathways using cell type-specific promoters and mutant signaling proteins in the postnatal retina. We have also observed that persistent CNTF signals trigger only transient retinal signal transduction, which correlates with an up-regulation of the cytokine signaling inhibitor SOCS3. We hypothesize that the negative regulation of cytokine signals by SOCS3 is critical for proper retinal development. To elucidate the function of SOCS3, we will misexpress SOCS3 and inhibit SOCS3 expression by RNA interference-mediated gene inhibition. It has been shown that viral mediated CNTF expression in the rds mutant retina rescues photoreceptor cell death, but causes abnormal cell morphology and retinal function. We will characterize signaling events in CNTF treated rds retina and test if the survival of photoreceptors is mediated by cytokine activated Muller glia. We have also begun to screen for cytokine target genes in the postnatal retina by microarray analyses. Potential candidate target genes will be validated by RT-PCR, in situ hybridization, Western blot, and promoter sequence analyses. Interactions between STAT transcription factors and target gene promoters will be examined by promoter binding assays. These proposed studies will advance our understanding of cytokine signaling mechanisms in the normal developing retina and in a mutant model of photoreceptor degeneration.

[unreadable] DESCRIPTION (provided by applicant): In Usher syndrome, deaf patients also develop retinitis pigmentosa. Usher syndrome type 1B has been associated with mutations in the myosin Vlla gene (MYO7A). In the mammalian eye, myosin VIla protein is located in the cilium of photoreceptor cells and in the apical region of the retinal pigmented epithelial (RPE) cells. Shaker1 mice also carry mutations in the myosin Vlla gene, and several mutant phenotypes have now been identified in the retinas of these mice. The proposed research aims to determine the efficacy of gene therapy for myosin Vlla deficiency in the shaker1 mouse. High titer lentiviruses co-expressing the human myosin Vlla protein and the green fluorescent protein (GFP) will be produced and injected into the sub-retinal space of newborn mice. The efficiency of viral infection and transgene transduction in photoreceptors and RPE cells will be determined by monitoring expression patterns of myosin Vlla and GFP. The rescuing effects of the viral mediated myosin Vlla expression will be determined by assaying previously identified mutant phenotypes in the retinas of shaker1 mice: e.g., the subcellular distribution of the pigment granules in the RPE cells, the distribution of rhodopsin in the photoreceptor connecting cilium, and the phagocytosis of the outer segment disks by the RPE cells. The proposed research will provide data directly relevant to the feasibility of gene therapy for the Usher 1 B syndrome in humans and to the application of lentivirus as a gene therapy vehicle for other inherited retinal diseases.

[unreadable] DESCRIPTION (provided by applicant): In Usher syndrome, deaf patients also develop retinitis pigmentosa. Usher syndrome type 1B has been associated with mutations in the myosin Vlla gene (MYO7A). In the mammalian eye, myosin VIla protein is located in the cilium of photoreceptor cells and in the apical region of the retinal pigmented epithelial (RPE) cells. Shaker1 mice also carry mutations in the myosin Vlla gene, and several mutant phenotypes have now been identified in the retinas of these mice. The proposed research aims to determine the efficacy of gene therapy for myosin Vlla deficiency in the shaker1 mouse. High titer lentiviruses co-expressing the human myosin Vlla protein and the green fluorescent protein (GFP) will be produced and injected into the sub-retinal space of newborn mice. The efficiency of viral infection and transgene transduction in photoreceptors and RPE cells will be determined by monitoring expression patterns of myosin Vlla and GFP. The rescuing effects of the viral mediated myosin Vlla expression will be determined by assaying previously identified mutant phenotypes in the retinas of shaker1 mice: e.g., the subcellular distribution of the pigment granules in the RPE cells, the distribution of rhodopsin in the photoreceptor connecting cilium, and the phagocytosis of the outer segment disks by the RPE cells. The proposed research will provide data directly relevant to the feasibility of gene therapy for the Usher 1 B syndrome in humans and to the application of lentivirus as a gene therapy vehicle for other inherited retinal diseases.

Abstract The Hedgehog (Hh) family of proteins plays important roles in the determination of neuronal cell fates and the maintenance of adult neural stem cell potentials. Previous studies and our preliminary results indicate that Sonic hedgehog (Shh) promotes retinal progenitor cell proliferation and affects specification of early born retinal neurons. However, the precise function of Hh signaling in mammalian photoreceptor cell development and survival is not well understood. The proposed research will use molecular genetic approaches to elucidate the roles of Hh signaling during mouse photoreceptor development and maintenance. The essential Hh receptor component Smoothened (Smo) will be eliminated by Cre/loxP recombination using transgenic mouse lines and retroviruses expressing Cre recombinase. The effects of disrupting Hh signaling on postnatal progenitor proliferation and cell fate commitment, and on photoreceptor differentiation and morphogenesis will be analyzed using molecular markers and electron microscopy. The roles of Hh signaling in photoreceptor maintenance and survival will be characterized by ablating the Smo gene or the Shh gene in the mature retina followed by functional and morphological analyses. Results of the proposed research will elucidate the function of an important signaling pathway in mammalian photoreceptor differentiation and survival. Moreover, these studies will provide new insights into mechanisms of photoreceptor degeneration and opportunities to develop novel therapies for combating retinal diseases.

? DESCRIPTION (provided by applicant): Ciliary neurotrophic factor (CNTF) acts as a potent neuroprotective agent in a variety of retinal degeneration animal models. In recent years, CNTF secreted from an encapsulated cell device has been evaluated in several clinical trials, and the FDA has granted this CNTF therapy an Orphan Drug Status for the treatment of retinitis pigmentosa (RP) and dry age-related macular degeneration (AMD). Yet despite the potential of CNTF as a broad-spectrum therapeutic agent for different blinding diseases, its mechanisms of action in the retina remain poorly understood. We have shown previously that constitutive, high-level expression of CNTF prevents photoreceptor death but alters retinal gene expression and suppresses visual function. Recently, we have explored the mechanism of CNTF action using genetic perturbations in an RP mouse model treated with the same human CNTF used in clinical trials. By performing retinal cell type specific gene deletions, we have shown that the initial targets of CNTF are Müller glial cells, and without a functional cytokine receptor in Müler glia, downstream signaling events and CNTF-induced photoreceptor survival are abolished. Although the rod photoreceptors do not directly respond to exogenous CNTF, they also require a functional cytokine receptor for survival. Furthermore, we have provided evidence that exogenous CNTF stimulates and amplifies a signaling loop between Müller glia and photoreceptors to promote neuronal viability. However, despite a significant improvement in photoreceptor morphology and viability, low levels of exogenous CNTF only stabilize but do not further enhance retinal function. The proposed research will combine advanced molecular genetics and system biology approaches to investigate the mechanisms underlying CNTF-induced neuroprotection in the retina. We will determine the functions of specific signaling modalities activated by CNTF in rod photoreceptors and Müller glia by using genetically modified mice. We will analyze CNTF-induced changes at the epigenome and transcriptome levels in rod cells by comparing wild type and mutant retinas to decipher critical cellular processes affecting cell survival and function. We will also evaluate the effect of CNTF treatment on cellular metabolism in diseased retinas and define the signaling effector mediating the effect. The proposed research will advance our understanding of neuroprotection mechanisms, provide insight into the effects of CNTF in human retinas, and facilitate the development of more efficacious treatments for retinal degeneration.

PROJECT SUMMARY ? GCD CORE The Gene and Cell Delivery (GCD) core will be a new component of the UCLA vision research core grant. The establishment of this core is in response to the research demands by UCLA vision scientists to deliver reagents to the retina, RPE, and other ocular tissues for the purpose of investigating basic mechanisms and preclinical testing of therapeutic potentials. The GCD core is consist of a biosafety level 2 (BSL2) viral vector production facility and a facility for have a technical staff with molecular biology, cell culture, recombinant virus preparation expertise. Ideally, the GCD staff will also have experiences of operating injection instrument and can teach members of individual laboratories to perform subretinal and intravitreal delivery in neonatal and adult rodents. The GCD core will provide support for the production of recombinant viral vectors, mainly rAAVs and lentiviruses. A website will be set up to provide available viral vector backbone information and for individual labs to submit requests. Under the supervision of the core component director Dr. X-J Yang, the GCD staff will use viral vector constructs and other necessary reagents provided by individual investigator labs to perform transfection, harvesting, viral concentration, and tittering procedures. The viral stocks produced by the GCD core will be tested by labs of individual investigators. The GCD core is equipped with necessary microscopes and micromanipulators to perform intraocular injections in a designed BSL2 animal facility. The reagents to be delivered using these equipment/instruments can range from nucleic acids, protein conjugates, nanoparticles, recombinant viruses, small molecules, and human stem cell-derived cells. The same facility can house post-operative mice deemed to need BSL2 containment. The GCD core is expected to facilitate basic and preclinical research supported by NIH/NEI on UCLA campus by providing effective tools and by enabling intraocular delivery in animal models. 1