Biomedical subjects

Samuel G Jacobson

Publications and source records attributed to Samuel G Jacobson.

At least 37 records · Page 2Linked to original sources

PubMed2005

Nonhuman primate models for diabetic ocular neovascularization using AAV2-mediated overexpression of vascular endothelial growth factor.

Neovascularization leads to blindness in numerous ocular diseases, including diabetic retinopathy, age-related macular degeneration, retinopathy of prematurity, and sickle cell disease. More effective and stable treatments for ocular neovascularization are needed, yet there are major limitations in the present animal models. To develop primate models of diabetic retinopathy and choroidal neovascularization, rhesus monkeys were injected subretinally or intravitreally with an adeno-associated virus (AAV)-2 vector carrying the cDNA encoding human vascular endothelial growth factor (VEGF). Overexpression of VEGF was measured by intraocular fluid sampling over time. Neovascularization was evaluated by ophthalmoscopy through angiography, optical coherence tomography, and ultimately histopathology. Overexpression of VEGF through AAV2 results in rapid development of features of diabetic retinopathy or macular edema, depending on the targeted cell type/mode of production of VEGF and diffusion of VEGF. Nonhuman primate models will be useful in testing long-term safety and efficacy of novel therapeutic agents for blinding neovascular diseases.

Adenoviridae↗

PubMed2004

Nuclear receptor NR2E3 gene mutations distort human retinal laminar architecture and cause an unusual degeneration.

Mutations in the nuclear receptor gene, NR2E3, cause a disorder of human retinal photoreceptor development characterized by hyperfunction and excess of the minority S (short wavelength or blue) cone photoreceptor type, but near absence of function of the majority rod receptor. NR2E3 disease can also progress to blindness. How the human retina accommodates mis-specified types and numbers of neurons and advances to retinal degeneration are unknown. We studied the retinal organization in vivo of patients with NR2E3 mutations. Early human NR2E3 disease with S cone hyperfunction showed thickened retinal layers within an otherwise normally structured retina. With visual loss, however, lamination was coarse and there was a strikingly thick and bulging appearance to the retina, localized to an annulus encircling the central fovea. This pattern was not found in other retinal degenerations. The abnormal laminar retinal architecture of early NR2E3 disease may be due in part to larger cells with an S cone phenotype in place of rods that failed to differentiate. The later-stage dysplastic appearance suggests a previously unrecognized proliferative response in human retinal degeneration.

Humans↗

PubMed2004

QRX, a novel homeobox gene, modulates photoreceptor gene expression.

A novel paired-like homeobox gene, designated as Qrx, was identified by a yeast one-hybrid screen using the bovine Rhodopsin promoter Ret-1 DNA regulatory element as bait. Qrx is preferentially expressed in both the outer and inner nuclear layers of the retina. Its homeodomain is nearly identical to that of Rx/Rax, a transcription factor that is essential for eye development, but it shares only limited homology elsewhere. Although Qrx and Rx/Rax show similar DNA binding properties in vitro, the two proteins demonstrate distinct target selectivity and functional behavior in promoter activity assays. QRX synergistically increases the transactivating function of the photoreceptor transcription factors Crx and NRL and it physically interacts with CRX. Qrx is present in the bovine and human genomes, but appears to be absent from the mouse genome. Nonetheless, a 5.8 kb upstream region of human QRX is capable of directing expression in presumptive photoreceptor precursor cells in transgenic mice. These results indicate that Qrx may be involved in modulating photoreceptor gene expression. In addition, the finding of rare heterozygous QRX sequence changes in three individuals with retinal degeneration raises the possibility that QRX may be involved in disease pathogenesis.

Amino Acid Sequence↗

PubMed2004

Age-related macular degeneration: a high-resolution genome scan for susceptibility loci in a population enriched for late-stage disease.

Age-related macular degeneration (AMD) is a complex multifactorial disease that affects the central region of the retina. AMD is clinically heterogeneous, leading to geographic atrophy (GA) and/or choroidal neovascularization (CNV) at advanced stages. Considerable data exists in support of a genetic predisposition for AMD. Recent linkage studies have provided evidence in favor of several AMD susceptibility loci. We have performed a high-resolution (5-cM) genome scan of 412 affected relative pairs that were enriched for late-stage disease (GA and/or CNV). Nonparametric linkage analysis was performed using two different diagnostic criteria and also by dividing the affected individuals according to GA or CNV phenotype. Our results demonstrate evidence of linkage in regions that were suggested in at least one previous study at chromosomes 1q (236-240 cM in the Marshfield genetic map), 5p (40-50 cM), and 9q (111 cM). Multipoint analysis of affected relatives with CNV provided evidence of additional susceptibility loci on chromosomes 2p (10 cM) and 22q (25 cM). A recently identified Gln5345Arg change in HEMICENTIN-1 on chromosome 1q25 was not detected in 274 affected members in the restricted group with AMD, 346 additional patients with AMD, and 237 unaffected controls. Our results consolidate the chromosomal locations of several AMD susceptibility loci and, together with previous reports, should facilitate the search for disease-associated sequence variants.

Aging↗

PubMed2004

Mutations in ABCA4 result in accumulation of lipofuscin before slowing of the retinoid cycle: a reappraisal of the human disease sequence.

Mutations in ABCA4, which encodes a photoreceptor specific ATP-binding cassette transporter (ABCR), cause autosomal recessive forms of human blindness due to retinal degeneration (RD) including Stargardt disease. The exact disease sequence leading to photoreceptor and vision loss in ABCA4-RD is not known. Extrapolation from murine and in vitro studies predicts that two of the earliest pathophysiological features resulting from disturbed ABCR function in man would be slowed kinetics of the retinoid cycle and accelerated deposition of lipofuscin in the retinal pigment epithelium (RPE). To determine the human pathogenetic sequence, we studied surrogate measures of retinoid cycle kinetics, lipofuscin accumulation, and rod and cone photoreceptor and RPE loss in ABCA4-RD patients with a wide spectrum of disease severities. There were different extents of photoreceptor/RPE loss and lipofuscin accumulation in different regions of the retina. Slowing of retinoid cycle kinetics was not present in all patients; when present, it was not homogeneous across the retina; and the extent of slowing correlated well with the degree of degeneration. The orderly relationship between these phenotypic features permitted the development of a model of disease sequence in ABCA4-RD. The model predicted lipofuscin accumulation as a key and early component of the disease expression in man, as in mice. In man, however, abnormal slowing of the rod and cone retinoid cycle occurs at later stages of the disease sequence. Knowledge of the human ABCA4 disease sequence will be critical for defining rates of progression, selecting appropriate patients and retinal locations for future therapy, and choosing appropriate treatment outcomes.

ATP-Binding Cassette Transporters↗

PubMed2004

Mutation analysis of NR2E3 and NRL genes in Enhanced S Cone Syndrome.

Ten new and seventeen previously reported Enhanced S Cone Syndrome (ESCS) subjects were used to search for genetic heterogeneity. All subjects were diagnosed with ESCS on the basis of clinical, psychophysical and/or electroretinography testing using published criteria. Mutation analysis was performed on the NR2E3 nuclear receptor gene by single strand conformation analysis and direct sequencing, which revealed either homozygous (N=13) or compound heterozygous (N=11) mutations in 24 subjects (89%), heterozygous mutations in 2 subjects (7%) and no mutations in 1 subject (4%). Fifteen different mutations were identified, including six not previously reported. The subject (Patient A) with no detected NR2E3 mutation had features not usually associated with ESCS, in particular moderate rod photoreceptor function in peripheral retina and an abnormally thick retinal nerve fibre layer. Mutation analysis of the NRL, CRX, NR1D1 and THRB genes in this individual revealed a heterozygous one base-pair insertion in exon 2 of the NRL gene, which results in a predicted truncation of the NRL protein. Loss-of-function NRL alleles have not been described previously in humans, but since the same mutation was present in unaffected family members, it raises the possibility that the abnormal ESCS phenotype in Patient A may result from a digenic mechanism, with a heterozygous NRL mutation and a mutation in another unknown gene.

Abnormalities, Multiple↗

PubMed2004

In utero gene therapy rescues vision in a murine model of congenital blindness.

The congenital retinal blindness known as Leber congenital amaurosis (LCA) can be caused by mutations in the RPE65 gene. RPE65 plays a critical role in the visual cycle that produces the photosensitive pigment rhodopsin. Recent evidence from human studies of LCA indicates that earlier rather than later intervention may be more likely to restore vision. We determined the impact of in utero delivery of the human RPE65 cDNA to retinal pigment epithelium cells in a murine model of LCA, the Rpe65(-/-) mouse, using a serotype 2 adeno-associated virus packaged within an AAV1 capsid (AAV2/1). Delivery of AAV2/1-CMV-hRPE65 to fetuses (embryonic day 14) resulted in efficient transduction of retinal pigment epithelium, restoration of visual function, and measurable rhodopsin. The results demonstrate AAV-mediated correction of the deficit and suggest that in utero retinal gene delivery may be a useful approach for treating a variety of blinding congenital retinal diseases.

Animals↗

PubMed2004

Lifespan and mitochondrial control of neurodegeneration.

We examine the allometric (comparative scaling) relationships between rates of neurodegeneration resulting from equivalent mutations in a diverse group of genes from five mammalian species with different maximum lifespan potentials. In both retina and brain, rates of neurodegeneration vary by as much as two orders of magnitude and are strongly correlated with maximum lifespan potential and rates of formation of mitochondrial reactive oxygen and nitrogen species (RONS). Cell death in these disorders is directly or indirectly regulated by the intrinsic mitochondrial cell death pathway. Mitochondria are the main source of RONS production and integrate cellular stress signals to coordinate the intrinsic pathway. We propose that these two functions are intimately related and that steady-state RONS-mediated signaling or damage to the mitochondrial stress-integration machinery is the principal factor setting the probability of cell death in response to a diverse range of cellular stressors. This provides a new and unifying framework for investigating neurodegenerative disorders.

Animals↗

PubMed2004

Impairment of the transient pupillary light reflex in Rpe65(-/-) mice and humans with leber congenital amaurosis.

PURPOSE: To determine the impairment of the transient pupillary light reflex (TPLR) due to severe retinal dysfunction and degeneration in a murine model of Leber congenital amaurosis (LCA) and in patients with the disease. METHODS: Direct TPLR was elicited in anesthetized, dark-adapted Rpe65(-/-) and control mice with full-field light stimuli (0.1 second duration) of increasing intensities (-6.6 to +2.3 log scot-cd. m(-2)). 9-cis-Retinal was administered orally to a subset of Rpe65(-/-) mice, and TPLR was recorded 48 hours after the treatment. TPLR was also measured in a group of patients with LCA. RESULTS: Baseline pupillary diameters in Rpe65(-/-) and control mice were similar. TPLR thresholds of Rpe65(-/-) mice were elevated by 5 log units compared with those of control animals. The waveform of the TPLR in Rpe65(-/-) mice was similar to that evoked by 4.8-log-unit dimmer stimuli in control mice. Treatment of Rpe65(-/-) mice with 9-cis-retinal lowered the TPLR threshold by 2.1 log units. Patients with LCA had baseline pupillary diameters similar to normal, but the TPLR was abnormal, with thresholds elevated by 3 to more than 6 log units. When adjusted to the elevation of TPLR threshold, pupillary constriction kinetics in most patients were similar to those in normal subjects. CONCLUSIONS: Pupillometry was used to quantify visual impairment and to probe transmission of retinal signals to higher nervous centers in a murine model of LCA and in patients with LCA. Mouse results were consistent with a dominant role of image-forming photoreceptors driving the early phase of the TPLR when elicited by short-duration stimuli. The objective and noninvasive nature of the TPLR measurement, and the observed post-treatment change toward normal in the animal model supports the notion that this may be a useful outcome measure in future therapeutic trials of LCA.

Adolescent↗

PubMed2003

Mutation in a short-chain collagen gene, CTRP5, results in extracellular deposit formation in late-onset retinal degeneration: a genetic model for age-related macular degeneration.

A primary feature of age-related macular degeneration (AMD) is the presence of extracellular deposits between the retinal pigment epithelium (RPE) and underlying Bruch's membrane, leading to RPE dysfunction, photoreceptor death and severe visual loss. AMD accounts for about 50% of blind registrations in Western countries and is a common, genetically complex disorder. Very little is known regarding its molecular basis. Late-onset retinal degeneration (L-ORD) is an autosomal dominant disorder with striking clinical and pathological similarity to AMD. Here we show that L-ORD is genetically heterogeneous and that a proposed founder mutation in the CTRP5 (C1QTNF5) gene, which encodes a novel short-chain collagen, changes a highly conserved serine to arginine (Ser163Arg) in 7/14 L-ORD families and 0/1000 control individuals. The mutation occurs in the gC1q domain of CTRP5 and results in abnormal high molecular weight aggregate formation which may alter its higher-order structure and interactions. These results indicate a novel disease mechanism involving abnormal adhesion between RPE and Bruch's membrane.

Age of Onset↗

PubMed2003

Crumbs homolog 1 (CRB1) mutations result in a thick human retina with abnormal lamination.

Mutations in CRB1, the human homolog of Drosophila Crumbs, cause autosomal recessive blinding disorders of the retina. Whereas Crumbs is implicated in apical-basal epithelial polarity and photoreceptor morphogenesis, the role of CRB1 in normal or diseased retina remains unclear. We characterized the retinal organization in vivo of patients with CRB1 mutations and found that, unlike other inherited retinal degenerations studied to date, the CRB1 mutant retinas are remarkably thick in cross-section and lack the distinct layers of normal adult retina. There are coarse outer and inner zones and a thick surface layer around the optic nerve. The abnormal retinal architecture in CRB1 mutations resembles that of immature normal retina. The results suggest that the CRB1 disease pathway disturbs the development of normal human retinal organization by interrupting naturally occurring apoptosis.

Eye Proteins↗

PubMed2003

Mutation screening of patients with Leber Congenital Amaurosis or the enhanced S-Cone Syndrome reveals a lack of sequence variations in the NRL gene.

PURPOSE: To determine if mutations in the retinal transcription factor gene NRL are associated with retinopathies other than autosomal dominant retinitis pigmentosa (adRP). METHODS: Genomic DNA was isolated from blood samples obtained from 50 patients with Leber Congenital Amaurosis (LCA), 17 patients with the Enhanced S-Cone Syndrome (ESCS), and a patient with an atypical retinal degeneration that causes photoreceptor rosettes with blue cone opsin. The 5' upstream region (putative promoter), untranslated exon 1, coding exons 2 and 3, and exon-intron boundaries of the NRL gene were analyzed by direct sequencing of the PCR-amplified products. RESULTS: Complete sequencing of the NRL gene in DNA samples from this cohort of patients revealed only one nucleotide change. The C->G transversion at nucleotide 711 of NRL exon 3 was detected in one LCA patient; however, this change did not alter the amino acid (L237L). CONCLUSIONS: No potential disease causing mutation was identified in the NRL gene in patients with LCA, ESCS, or the atypical retinal degeneration. Together with previous studies, our results demonstrate that mutations in the NRL gene are not a major cause of retinopathy. To date, only missense changes have been reported in adRP patients, and sequence variations are rare. It is possible that the loss of NRL function in humans is associated with a more complex clinical phenotype due to its expression in pineal gland in addition to rod photoreceptors.

Basic-Leucine Zipper Transcription Factors↗

PubMed2003

Evaluation of complex inheritance involving the most common Bardet-Biedl syndrome locus (BBS1).

Bardet-Biedl syndrome (BBS) is a genetic disorder with the primary features of obesity, pigmentary retinopathy, polydactyly, renal malformations, mental retardation, and hypogenitalism. Patients with BBS are also at increased risk for diabetes mellitus, hypertension, and congenital heart disease. BBS is known to map to at least six loci: 11q13 (BBS1), 16q21 (BBS2), 3p13-p12 (BBS3), 15q22.3-q23 (BBS4), 2q31 (BBS5), and 20p12 (BBS6). Although these loci were all mapped on the basis of an autosomal recessive mode of inheritance, it has recently been suggested-on the basis of mutation analysis of the identified BBS2, BBS4, and BBS6 genes-that BBS displays a complex mode of inheritance in which, in some families, three mutations at two loci are necessary to manifest the disease phenotype. We recently identified BBS1, the gene most commonly involved in Bardet-Biedl syndrome. The identification of this gene allows for further evaluation of complex inheritance. In the present study we evaluate the involvement of the BBS1 gene in a cohort of 129 probands with BBS and report 10 novel BBS1 mutations. We demonstrate that a common BBS1 missense mutation accounts for approximately 80% of all BBS1 mutations and is found on a similar genetic background across populations. We show that the BBS1 gene is highly conserved between mice and humans. Finally, we demonstrate that BBS1 is inherited in an autosomal recessive manner and is rarely, if ever, involved in complex inheritance.

Amino Acid Sequence↗

PubMed2003

In vivo micropathology of Best macular dystrophy with optical coherence tomography.

Best macular dystrophy (BMD) is an autosomal dominant retinopathy caused by mutations in the VMD2 gene that encodes a chloride channel in the basolateral membrane of the retinal pigment epithelium (RPE). BMD patients were studied using optical coherence tomography (OCT) to understand the disease process in the macula leading to vision loss. BMD patients (ages 5-61), representing four families with known VMD2 mutations, were included. OCT scans were recorded in the central retina and longitudinal reflectivity profiles were analysed. The central retina in BMD showed different OCT abnormalities at or near the level of the highly reflective deep retinal band termed the outer retina-choroid complex (ORCC). Two types of ORCC change were noted to occur either separately or together: (1) splitting with or without intervening hyporeflective areas; and (2) elevation. Longitudinal study of a BMD patient indicated that such abnormalities were dynamic and changed in type and degree with time. The pathogenetic sequence in BMD may begin with defective fluid transport across the RPE secondary to the channelopathy in the basolateral membrane. In the macula, this leads to an abnormal interface with adjacent structures at both apical and basal surfaces of the RPE. The disease process results in detachments of the neurosensory retina, such as in central serous chorioretinopathy, and sub-RPE pathology resembling some stages of age-related macular degeneration, with eventual loss of photoreceptors, inner retina and central vision.

Adult↗

PubMed2003

Clinicopathologic effects of mutant GUCY2D in Leber congenital amaurosis.

PURPOSE: To study the retinal degeneration in an 11 -year-old patient with Leber congenital amaurosis (LCA) caused by mutation in GUCY2D. STUDY DESIGN: Comparative human tissue study. PARTICIPANTS: Two subjects with LCA; postmortem eye from one LCA patient and three normal donors. METHODS: Clinical and visual function studies were performed between the ages of 6 and 10 years in the LCA eye donor and at age 6 in an affected sibling. Genomic DNA was screened for mutations in known LCA genes. The retina of the 11 -year-old subject with LCA was compared with normal retinas from donors age 3 days, 18 years, and 53 years. The tissues were processed for histopathologic studies and immunofluorescence with retinal cell-specific antibodies. RESULTS: Vision in both siblings at the ages examined was limited to severely impaired cone function. Mutation in the GUCY2D gene was identified in both siblings. Histopathologic study revealed rods and cones without outer segments in the macula and far periphery. The cones formed a monolayer of cell bodies, but the rods were clustered and had sprouted neurites in the periphery. Rods and cones were not identified in the midperipheral retina. The inner nuclear layer appeared normal in thickness throughout the retina, but ganglion cells were reduced in number. CONCLUSIONS: An 11-year-old subject with LCA caused by mutant GUCY2D had only light perception but retained substantial numbers of cones and rods in the macula and far periphery. The finding of numerous photoreceptors at this age may portend well for therapies designed to restore vision at the photoreceptor level.

Adolescent↗

PubMed2003

Cone deactivation kinetics and GRK1/GRK7 expression in enhanced S cone syndrome caused by mutations in NR2E3.

PURPOSE: To determine the relationship between cone deactivation kinetics in patients with the enhanced S cone syndrome (ESCS) caused by mutations in NR2E3 and the immunoreactivity to G-protein-coupled receptor kinase 1 (GRK1) and GRK7. METHODS: Electroretinogram (ERG) photoresponses were used to investigate activation kinetics of cones with a model of cone phototransduction. Deactivation kinetics of cones after bright flashes was quantified with a paired-flash ERG paradigm. Immunocytochemistry was performed with antibodies against cone opsins and kinases GRK1 and GRK7 in postmortem normal and ESCS retinal tissue. RESULTS: Activation kinetics of long/middle-wavelength-sensitive (L/M) cone-mediated responses in patients with ESCS were similar to those of normal L/M cones. Activation kinetics of ESCS short-wavelength-sensitive (S) cones, when compared with normal L/M cone responses evoked by the same stimulus, were slower by an amount consistent with the expected differences in spectral sensitivities. After bright flashes chosen to evoke identical activation kinetics, ESCS S cones deactivated much more slowly than ESCS or normal L/M cones. Normal human retina revealed strongly labeled cone outer segments with anti-GRK1 and anti-GRK7. In an ESCS retina, outer segments positive for L/M opsin were strongly labeled with anti-GRK1, whereas outer segments positive for S opsin showed no detectable GRK1 reactivity. GRK7 labeling was absent in all photoreceptors of the ESCS retina. CONCLUSIONS: The cone-dominant human retina resulting from NR2E3 mutations affords greater understanding of the physiological roles of GRK1 and GRK7 in human cone photoreceptors. Normal deactivation kinetics in human L/M cones can occur without GRK7 when GRK1 is present in ESCS, but does not occur when GRK7 is present but GRK1 is deficient in Oguchi disease. Lack of both GRK1 and GRK7 in S cones of patients with ESCS results in a more pronounced abnormality in deactivation kinetics and suggests the existence of partial compensation by either GRK when the other is deficient.

Electroretinography↗

PubMed2003

De novo mutation in the RP1 gene (Arg677ter) associated with retinitis pigmentosa.

PURPOSE: The Arg677ter mutation in the RP1 gene is one of the most common causes of autosomal dominant retinitis pigmentosa (RP). In the current study, a de novo Arg677ter RP1 gene mutation was identified in a patient with RP. METHODS: RP1 gene mutation screening was performed in probands with simplex RP. In one proband with the RP1 mutation, paternity was established by analyzing 24 short tandem repeat polymorphisms. Additional candidate RP genes, including rhodopsin, RDS/peripherin, RP2, and RPGR, were also examined in this proband. Phenotype was characterized with psychophysics, electroretinography, and optical coherence tomography. RESULTS: An RP1 (Arg677ter) mutation was identified in one of the patients with simplex RP, but the sequence change was not detected in his parents. Parentage was confirmed, and other candidate genes were negative for mutations. Retinal function and cross-sectional imaging studies in the patient indicated greater rod than cone dysfunction with a photoreceptor basis for the abnormalities. CONCLUSIONS: The de novo origin of an RP1 (Arg677ter) mutation in a patient with simplex RP suggests that this common autosomal dominant RP mutation can arise independently in the population and supports the hypothesis of a mutational hotspot in the RP1 gene.

Adult↗

PubMed2002

Usher syndrome type III: revised genomic structure of the USH3 gene and identification of novel mutations.

Usher syndrome type III is an autosomal recessive disorder characterized by progressive sensorineural hearing loss, vestibular dysfunction, and retinitis pigmentosa. The disease gene was localized to 3q25 and recently was identified by positional cloning. In the present study, we have revised the structure of the USH3 gene, including a new translation start site, 5' untranslated region, and a transcript encoding a 232-amino acid protein. The mature form of the protein is predicted to contain three transmembrane domains and 204 residues. We have found four new disease-causing mutations, including one that appears to be relatively common in the Ashkenazi Jewish population. We have also identified mouse (chromosome 3) and rat (chromosome 2) orthologues, as well as two human paralogues on chromosomes 4 and 10.

5' Untranslated Regions↗