Mutations inSCAPERcause autosomal recessive retinitis pigmentosa with intellectual disability
Yasmin TatourIker Sánchez‐NavarroElana ChervinskyHákon HákonarsonHaithum GawiSaoud Tahsin SwafiriRina LeibuMaría Isabel López-MolinaGuillermo Fernández‐SanzCarmen AyusoTamar Ben‐Yosef
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Retinitis pigmentosa (RP) is the most common form of inherited retinal dystrophy, with a worldwide prevalence of 1 in 4000 persons. While in most cases of RP, the disease is limited to the eye (non-syndromic), over 40 forms of syndromic RP have been described.To identify the genetic basis for syndromic RP in three unrelated families from Israel and Spain.Whole exome sequencing was conducted in one Israeli and two Spanish families segregating autosomal recessive RP with intellectual disability. Complete ophthalmic examination included best-corrected visual acuity, funduscopy, optical coherence tomography, fluorescein angiography, flash visual evoked potentials, and electroretinography. Reverse transcription (RT)-PCR and immunostaining were used to examine the spatial and temporal expression pattern of SCAPER.In all patients, biallelic SCAPER mutations were observed. Clinically, patients with SCAPER mutations show signs of typical RP. In addition, they have mild to moderate intellectual disability and attention-deficit/hyperactivity disorder. SCAPER was found to be ubiquitously expressed in a wide range of human tissues, including retina and brain. Furthermore, RT-PCR analysis revealed that in both mouse eye and brain, Scaper is expressed as early as embryonic day 14. In the mouse retina, SCAPER is located in multiple layers, including the retinal pigment epithelium, photoreceptor outer and inner segments, the inner plexiform layer and the ganglion cell layer.Deleterious SCAPER mutations were identified in four patients from three unrelated families of different ethnic backgrounds, thereby confirming the involvement of this gene in the aetiology of autosomal recessive syndromic RP.Keywords:
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Abstract The manner in which new cells are added to the growing adult goldfish retina was examined using 3 H‐thymidine radioutography. Cell proliferation leading to the formation of neurons is restricted to the retinal margin at the ora terminalis . New retina is added in concentric rings, with slightly more growth dorsonasally. The rate of cell addition is variable, averaging 12,000 cells/ day. These new cells account for about 20% of the total increase in retinal area; the remaining 80% is due to hypertrophy, or expansin, of the retina. In contrast to all of the other retinal cells, the rods do not appear to participate in the retinal expansion. This hypothesized immobility of the rods would create a shearing strain between the retinal layers resulting in a shift in their position relative to the other cells. Were they to maintain synaptic contacts with the same horizontal and bipolar cells, the rod axons would have to be elongated peripherally or the post‐synaptic cell dendrites displaced centrally. Since neurons with this morphology have not been found in the goldfish retina, these observations suggest that the rods must be changing their synaptic connections as the retina grows.
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Psychophysical and electroretinographic (ERG) testing are used to evaluate retinal function in a Negro family with a recessively inherited retinitis pigmentosa. The abnormal ERGs with the autosomal recessive pattern of inheritance distinguish the retinal pigmentary degeneration in this family from other genetic types previously classified with electroretinography. All affected children have retinal disease visible with the ophthalmoscope. The youngest child has a reduction in amplitude and delay in timing of her cone ERG before any rod system abnormality can be detected. The older affected children have a reduction in amplitude and delay in implicit time of both cone and rod components. The reduced and delayed rod ERG to a relatively bright short wavelength light was simulated by presenting a relatively dim short wavelength light to normal subjects. The relative preservation of cone ERG amplitudes is discussed as a measure of severity of different types of retinitis pigmentosa in childhood.
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Abstract The pattern of retinal vasculative is described and the position at which cell proliferation at the ventral retinal margin is maximal was shown to be at the point of entry of the ventral blood vessels. To test whether there is a causal relation between retinal blood supply and retinal cell production, surgical inversion of the eye, transplantations and excisions of retina were done to change the pattern of retinal vasculature. The growth pattern of inverted eyes was normal with respect to the internal axes of the eyes. After excision of part of the retina or after fusion of retinal fragments to form compound eyes, the pattern of retinal cell proliferation was not correlated with the distribution of retinal blood vessels, but was correlated with the position(s) of the choroidal fissure(s).
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Rod- and cone-mediated function was studied with psychophysics and electroretinography in members of an X-linked retinitis pigmentosa pedigree with the RP2 genotype. An asymptomatic hemizygote with an early stage of the disease had cone dysfunction in the mid-periphery and an abnormal cone electroretinogram (ERG); rod function was normal. Hemizygotes with more advanced disease had cone and rod dysfunction in the mid-peripheral retina and cone dysfunction in the far periphery; cone and rod ERGs were abnormal. At very advanced stages, there was an absolute mid-peripheral scotoma and marked cone and rod dysfunction in the far peripheral and central retina. Cone and rod ERGs were severely abnormal or not detectable. Heterozygotes showed tapetal-like reflexes, patches of pigmentary retinopathy, and a range of functional findings from no detectable abnormalities to moderate levels of retinal dysfunction. There were regions of normal function adjacent to dysfunctional patches that had greater cone than rod sensitivity losses or comparable cone and rod losses. The results suggest that the phenotype of this RP2 genotype of X-linked retinitis pigmentosa, unlike other forms of retinitis pigmentosa, is first expressed as a cone photoreceptor system dysfunction, and as the disease progresses, both rod and cone systems are involved.
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Spatial Pattern and Temporal Evolution of Retinal Oxygenation Response in Oxygen-Induced Retinopathy
To determine the spatial pattern and temporal evolution of the change in retinal partial oxygen pressure (DeltaPO(2)) associated with a murine oxygen-induced retinopathy (OIR) model of retinal neovascularization (NV).On P7, newborn C57BL/6 mice were exposed to 75% oxygen until postnatal day (P)12, followed by recovery in room air until P17 or P34. Control mice remained in room air until P17 or P34. At P17 and P34, functional magnetic resonance imaging (MRI) and a carbogen inhalation challenge was used to measure retinal DeltaPO(2). Retinal avascularity, distance from the optic nerve head to the vascular edge in the peripheral retina, and NV incidence and severity were measured in retinas stained with adenosine diphosphatase (ADPase).In P17 and P34 controls and in P34 OIR animals, retinas were fully vascularized without evidence of NV. In P17 OIR mice, there was a large central retinal capillary-free zone (22% +/- 3% of the entire retinal area, mean +/- SD) and 4 clockhours (range 1-7) of retinal NV at the border of the peripheral vascular and central acapillary retina in 100% (36/36) of the mice. In P17 OIR mice, retinal DeltaPO(2) over the vascularized far peripheral retina was not significantly (P > 0.05) different from the P17 control but was supernormal (P < 0.05) over the central capillary-free retina. However, no differences (P > 0.05) in retinal DeltaPO(2) were found between the P34 control and OIR groups.A reversible supernormal DeltaPO(2) was found only over the central acapillary retina during the appearance of retinal NV in a mouse OIR model. The present data show the applicability of carbogen-challenge functional MRI to the study of retinal DeltaPO(2) in vivo in eyes that are too small for the use of existing techniques.
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The oxygen requirements of different retinal layers are of interest in understanding the vulnerability of the retina to hypoxic damage in retinal diseases with an ischemic component. Here, we report the first measurements of retinal oxygen consumption in the visual streak of the rabbit retina, the region with the highest density of retinal neurons, and compare it with that in the less-specialized region of the retina underlying the vascularized portion of the rabbit retina. Oxygen-sensitive microelectrodes were used to measure oxygen tension as a function of retinal depth in anesthetized animals. Measurements were performed in the region of the retina containing overlying retinal vessels and in the center of the visual streak. Established mathematical analyses of the intraretinal oxygen distribution were used to quantify the rate of oxygen consumption in the inner and outer retina and the relative oxygen contributions from the choroidal and vitreal sides. Outer retinal oxygen consumption was higher in the visual streak than in the vascularized area (means ± SE, 284 ± 20 vs. 210 ± 23 nl O 2 ·min –1 ·cm –2 , P = 0.026, n = 10). However, inner retinal oxygen consumption in the visual streak was significantly lower than in the vascular area (57 ± 4.3 vs. 146 ± 12 nl O 2 ·min –1 ·cm –2 , P < 0.001). We conclude that despite the higher processing requirements of the inner retina in the visual streak, it has a significantly lower oxygen consumption rate than the inner retina underlying the retinal vasculature. This suggests that the oxygen uptake of the inner retina is regulated to a large degree by the available oxygen supply rather than the processing requirements of the inner retina alone.
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Domestic pigs were fed with high lipid diet (HLD) for 24 weeks. Electroretinographic studies and the measurement of the diameter of retinal arterioles were investigated before and after the administration of HLD. The most significant change produced by HLD was negativization of electroretinogram. At the same time the diameter of retinal arterioles was significantly decreased.
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