RESUMO
Blue cone monochromacy (BCM) is a rare X-linked retinal disease characterized by the absence of L- and M-opsin in cone photoreceptors, considered a potential gene therapy candidate. However, most experimental ocular gene therapies utilize subretinal vector injection which would pose a risk to the fragile central retinal structure of BCM patients. Here we describe the use of ADVM-062, a vector optimized for cone-specific expression of human L-opsin and administered using a single intravitreal (IVT) injection. Pharmacological activity of ADVM-062 was established in gerbils, whose cone-rich retina naturally lacks L-opsin. A single IVT administration dose of ADVM-062 effectively transduced gerbil cone photoreceptors and produced a de novo response to long-wavelength stimuli. To identify potential first-in-human doses we evaluated ADVM-062 in non-human primates. Cone-specific expression of ADVM-062 in primates was confirmed using ADVM-062.myc, a vector engineered with the same regulatory elements as ADVM-062. Enumeration of human OPN1LW.myc-positive cones demonstrated that doses ≥3 × 1010 vg/eye resulted in transduction of 18%-85% of foveal cones. A Good Laboratory Practice (GLP) toxicology study established that IVT administration of ADVM-062 was well tolerated at doses that could potentially achieve clinically meaningful effect, thus supporting the potential of ADVM-062 as a one-time IVT gene therapy for BCM.
Assuntos
Opsinas , Células Fotorreceptoras Retinianas Cones , Animais , Humanos , Células Fotorreceptoras Retinianas Cones/metabolismo , Opsinas/genética , Primatas/genética , Primatas/metabolismo , Opsinas de Bastonetes/genética , Opsinas de Bastonetes/metabolismo , Terapia Genética/métodosRESUMO
Purpose: To evaluate the long-term safety of vascular endothelial growth factor (VEGF) suppression with sustained aflibercept expression after a single intravitreal injection (IVI) of ADVM-022, an anti-VEGF gene therapy, in non-human primates (NHPs). Methods: Non-human primates received bilateral IVI of ADVM-022, a gene therapy vector encoding aflibercept, a standard of care for the treatment of VEGF-based retinal disease. Aflibercept levels from ocular fluids and tissues were measured. Ocular inflammation was assessed by slit lamp biomicroscopy and fundoscopy. The integrity of the retinal structure was analyzed by optical coherence tomography and blue light fundus autofluorescence and electroretinography was performed to determine retinal function. Histologic evaluation of the retina was performed at the longest time point measured (2.5 years after injection). Results: Sustained expression of aflibercept was noted out to the last time point evaluated. Mild to moderate inflammatory responses were observed, which trended toward spontaneous resolution without anti-inflammatory treatment. No abnormalities in retinal structure or function were observed, as measured by optical coherence tomography and electroretinography, respectively. RPE integrity was maintained throughout the study; no histologic abnormalities were observed 2.5 years after ADVM-022 IVI. Conclusions: In non-human primates, long-term, sustained aflibercept expression and the resulting continuous VEGF suppression by a single IVI of ADVM-022, appears to be safe, with no measurable adverse effects on normal retinal structure and function evaluated out to 2.5 years. Translational Relevance: Together with the results from previous ADVM-022 preclinical studies, these data support the evaluation of this gene therapy candidate in clinical trials as a potential durable treatment for various VEGF-mediated ophthalmic disorders.
Assuntos
Inibidores da Angiogênese , Fator A de Crescimento do Endotélio Vascular , Animais , Terapia Genética , Primatas , Receptores de Fatores de Crescimento do Endotélio Vascular , Proteínas Recombinantes de FusãoRESUMO
BDNF signaling through its TrkB receptor plays a pivotal role in activity-dependent refinement of synaptic connectivity of retinal ganglion cells. Additionally, studies using TrkB knockout mice have suggested that BDNF/TrkB signaling is essential for the development of photoreceptors and for synaptic communication between photoreceptors and second order retinal neurons. Thus the action of BDNF on refinement of synaptic connectivity of retinal ganglion cells could be a direct effect in the inner retina, or it could be secondary to its proposed role in rod maturation and in the formation of rod to bipolar cell synaptic transmission. To address this matter we have conditionally eliminated TrkB within the retina. We find that rod function and synaptic transmission to bipolar cells is not compromised in these conditional knockout mice. Consistent with previous work, we find that inner retina neural development is regulated by retinal BDNF/TrkB signaling. Specifically we show here also that the complexity of neuronal processes of dopaminergic cells is reduced in conditional TrkB knockout mice. We conclude that retinal BDNF/TrkB signaling has its primary role in the development of inner retinal neuronal circuits, and that this action is not a secondary effect due to the loss of visual signaling in the outer retina.
Assuntos
Receptor trkB/fisiologia , Retina/crescimento & desenvolvimento , Retina/metabolismo , Animais , Fator Neurotrófico Derivado do Encéfalo/deficiência , Fator Neurotrófico Derivado do Encéfalo/genética , Fator Neurotrófico Derivado do Encéfalo/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Rede Nervosa/crescimento & desenvolvimento , Rede Nervosa/metabolismo , Receptor trkB/deficiência , Receptor trkB/genética , Segmento Externo da Célula Bastonete/metabolismo , Segmento Externo da Célula Bastonete/fisiologia , Transdução de Sinais/genética , Transdução de Sinais/fisiologiaRESUMO
CAPS-1 is required for Ca2+-triggered fusion of dense-core vesicles with the plasma membrane, but its site of action and mechanism are unknown. We analyzed the kinetics of Ca2+-triggered exocytosis reconstituted in permeable PC12 cells. CAPS-1 increased the initial rate of Ca2+-triggered vesicle exocytosis by acting at a rate-limiting, Ca2+-dependent prefusion step. CAPS-1 activity depended upon prior ATP-dependent priming during which PIP2 synthesis occurs. CAPS-1 activity and binding to the plasma membrane depended upon PIP2. Ca2+ was ineffective in triggering vesicle fusion in the absence of CAPS-1 but instead promoted desensitization to CAPS-1 resulting from decreased plasma membrane PIP2. We conclude that CAPS-1 functions following ATP-dependent priming as a PIP2 binding protein to enhance Ca2+-dependent DCV exocytosis. Essential prefusion steps in dense-core vesicle exocytosis involve sequential ATP-dependent synthesis of PIP2 and the subsequent PIP2-dependent action of CAPS-1. Regulation of PIP2 levels and CAPS-1 activity would control the secretion of neuropeptides and monoaminergic transmitters.
Assuntos
Proteínas de Ligação ao Cálcio/fisiologia , Exocitose/fisiologia , Fosfatidilinositol 4,5-Difosfato/metabolismo , Vesículas Secretórias/metabolismo , Animais , Cálcio/metabolismo , Cálcio/fisiologia , Proteínas de Ligação ao Cálcio/biossíntese , Proteínas de Ligação ao Cálcio/genética , Células PC12 , Fosfatidilinositol 4,5-Difosfato/antagonistas & inibidores , Ligação Proteica/fisiologia , Ratos , Ratos Endogâmicos , Proteínas de Transporte VesicularRESUMO
Sensory experience refines neuronal structure and functionality. The visual system has proved to be a productive model system to study this plasticity. In the neonatal retina, the dendritic arbors of a large proportion of ganglion cells are diffuse in the inner plexiform layer. With maturation, many of these arbors become monolaminated. Visual deprivation suppresses this remodeling. Little is known of the molecular mechanisms controlling maturational and experience-dependent refinement. Here, we tested the hypothesis that brain-derived neurotrophic factor (BDNF), which is known to regulate dendritic branching and synaptic function in the brain, modulates the developmental and visual experience-dependent refinement of retinal ganglion cells. We used a transgenic mouse line, in which a small number of ganglion cells were labeled with yellow fluorescence protein, to delineate their dendritic structure in vivo. We found that transgenic overexpression of BDNF accelerated the laminar refinement of ganglion cell dendrites, whereas decreased TrkB expression or retina-specific deletion of TrkB, the cognate receptor for BDNF, retarded it. BDNF-TrkB signaling regulated the maturational formation of new branches in ON but not the bilaminated ON-OFF ganglion cells. Furthermore, BDNF overexpression overrides the requirement for visual inputs to stimulate laminar refinement and dendritic branching of ganglion cells. These experiments reveal a previously unrecognized action of BDNF and TrkB in controlling cell-specific, experience-dependent remodeling of neuronal structures in the visual system.
Assuntos
Fator Neurotrófico Derivado do Encéfalo/fisiologia , Receptor trkB/fisiologia , Retina/crescimento & desenvolvimento , Retina/metabolismo , Vias Visuais/crescimento & desenvolvimento , Vias Visuais/metabolismo , Fatores Etários , Animais , Fator Neurotrófico Derivado do Encéfalo/biossíntese , Fator Neurotrófico Derivado do Encéfalo/genética , Humanos , Camundongos , Camundongos Transgênicos , Ratos , Receptor trkB/biossíntese , Receptor trkB/genética , Retina/fisiologia , Privação Sensorial/fisiologia , Visão Ocular/fisiologia , Vias Visuais/fisiologiaRESUMO
Ca2+-dependent activator protein for secretion (CAPS) is a cytosolic protein essential for the Ca2+-dependent fusion of dense-core vesicles (DCVs) with the plasma membrane and the regulated secretion of a subset of neurotransmitters. The mechanism by which CAPS functions in exocytosis and the means by which it associates with target membranes are unknown. We identified two domains in CAPS with distinct membrane-binding properties that were each essential for CAPS activity in regulated exocytosis. The first of these, a centrally located pleckstrin homology domain, exhibited three properties: charge-based binding to acidic phospholipids, binding to plasma membrane but not DCV membrane, and stereoselective binding to phosphatidylinositol 4,5-bisphosphate. Mutagenesis studies revealed that the former two properties but not the latter were essential for CAPS function. The central pleckstrin homology domain may mediate transient CAPS interactions with the plasma membrane during Ca2+-triggered exocytosis. The second membrane association domain comprising distal C-terminal sequences mediated CAPS targeting to and association with neuroendocrine DCVs. The CAPS C-terminal domain was also essential for optimal activity in regulated exocytosis. The presence of two membrane association domains with distinct binding specificities may enable CAPS to bind both target membranes to facilitate DCV-plasma membrane fusion.
Assuntos
Cálcio/química , Membrana Celular/metabolismo , Exocitose , Algoritmos , Sequência de Aminoácidos , Animais , Células COS , Relação Dose-Resposta a Droga , Proteínas de Fluorescência Verde , Imuno-Histoquímica , Metabolismo dos Lipídeos , Proteínas Luminescentes/metabolismo , Microscopia de Fluorescência , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Mutação , Células PC12 , Plasmídeos/metabolismo , Ligação Proteica , Estrutura Terciária de Proteína , Ratos , Proteínas Recombinantes de Fusão/metabolismo , TransfecçãoRESUMO
Ca2+-dependent activator protein for secretion (CAPS) 1 is an essential cytosolic component of the protein machinery involved in large dense-core vesicle (LDCV) exocytosis and in the secretion of a subset of neurotransmitters. In the present study, we report the identification, cloning, and comparative characterization of a second mammalian CAPS isoform, CAPS2. The structure of CAPS2 and its function in LDCV exocytosis from PC12 cells are very similar to those of CAPS1. Both isoforms are strongly expressed in neuroendocrine cells and in the brain. In subcellular fractions of the brain, both CAPS isoforms are enriched in synaptic cytosol fractions and also present on vesicular fractions. In contrast to CAPS1, which is expressed almost exclusively in brain and neuroendocrine tissues, CAPS2 is also expressed in lung, liver, and testis. Within the brain, CAPS2 expression seems to be restricted to certain brain regions and cell populations, whereas CAPS1 expression is strong in all neurons. During development, CAPS2 expression is constant between embryonic day 10 and postnatal day 60, whereas CAPS1 expression is very low before birth and increases after postnatal day 0 to reach a plateau at postnatal day 21. Light microscopic data indicate that both CAPS isoforms are specifically enriched in synaptic terminals. Ultrastructural analyses show that CAPS1 is specifically localized to glutamatergic nerve terminals. We conclude that at the functional level, CAPS2 is largely redundant with CAPS1. Differences in the spatial and temporal expression patterns of the two CAPS isoforms most likely reflect as yet unidentified subtle functional differences required in particular cell types or during a particular developmental period. The abundance of CAPS proteins in synaptic terminals indicates that they may also be important for neuronal functions that are not exclusively related to LDCV exocytosis.