ABCA4 and ROM1: implications for modification of the PRPH2-associated macular dystrophy phenotype

PURPOSE: To identify the causative mutation leading to autosomal dominant macular dystrophy, cone dystrophy, and cone-rod dystrophy in a five-generation family and to explain the high intrafamilial phenotypic variation by identifying possible modifier genes. METHODS: Fifteen family members were investigated by detailed ophthalmic and electrophysiologic phenotyping. Mutation screening was initially performed with microarrays that detect known mutations in genes associated with retinal degeneration. Furthermore, the patients' genomic DNA was analyzed by sequencing analysis of PRPH2, ABCA4, and ROM1. RESULTS: Heterozygous mutations were identified in three genes and showed five different combinations within the studied family. All clearly affected family members carried the heterozygous PRPH2 mutation p.R172W. Patients with heterozygous sequence alterations only in ROM1 (p.R229H) or ABCA4 (p.V2050L) showed a mild ocular phenotype and were otherwise asymptomatic. The phenotypic severity of patients carrying the PRPH2 mutation increased with an additional mutation in ROM1. Patients carrying all three mutations were the most severely affected. CONCLUSIONS: Features of a PRPH2-associated phenotype might be modulated by additional mutations in other genes (in this family ABCA4 and/or ROM1) accounting for intrafamilial variability and resulting in a cumulative effect worsening the phenotype. Families showing a variable macular dystrophy phenotype caused by mutations in PRPH2 should be tested for additional mutations in ABCA4 and ROM1, as they may alter the progression of the PRPH2 phenotype. This testing will influence genetic counseling, as patients with additional mutations may be confronted with a faster progression of visual loss

Disturbed visual system function in methionine synthase deficiency

BACKGROUND: Isolated functional methionine synthase deficiency occurs in the cblE and cblG defects of methylcobalamin metabolism and is one of a number of causes of severely elevated plasma homocysteine. Clinical features are predominantly of a neurological nature but also include functional restriction of the visual system manifesting as loss of visual acuity and nystagmus. As yet, the origin and pathogenesis of impaired vision have not been explained. MATERIALS AND METHODS: We investigated a patient who was proven by complementation analysis in cultured fibroblasts to belong to the cblG complementation group. Ganzfeld electroretinograms (ERG) and flash visual evoked potentials (VEP) were recorded over a period of 4 years. RESULTS: Amplitudes of all International Society for Clinical Electrophysiology of Vision (ISCEV) standard responses were below normal. The greatest reductions were of rod response to 24 microV, of standard combined response (SC) b-wave to 120 microV, of oscillatory potentials (OP) to 5 microV, of cone response b-wave to 35 microV, and of 30 Hz flicker response to 8 microV. Except for SC and cone a-waves at age 2.5 and 3.5 years, as well as cone b-wave at 3.5 years, amplitudes remained at a subnormal level at follow-up examinations. Implicit times were slightly prolonged (SC b-wave 6 ms, OPs 2 ms, cone b-wave 2 ms, 30 Hz flicker 4 ms) or fell within the normal range. Responses of the flash VEP were severely deformed but reproducible. CONCLUSIONS: This is the first report of detailed investigations of the visual system in a patient with isolated methionine synthase deficiency. Reduced oscillatory potentials suggest microvascular damage to the retina through homocysteine. Decreased photoreceptor function as well as ganglion cell loss as indicated by pathological flash VEPs may reflect a cytotoxic impact of homocysteine on neurons of the visual pathway

Das multifokale Elektroretinogramm: Vergleich von Scanning Laser Ophthalmoskop – und Monitorstimulation (The multifocal electroretinogram: comparison of scanning laser ophthalmoscope and monitor stimulation).

Background. Multifocal electroretinograms (mfERG) were recorded using a confocal scanning laser ophthalmoscope (cSLO) and compared to the results from conventional monitor stimulation. Methods. Single and repeated measurements were recorded from 23 normal subjects using the cSLO (Heidelberg Retina Angiograph, Heidelberg Engineering, Heidelberg) as well as a conventional monitor as stimulation devices. Laser power output was modified by various optical filters. The reliability of the method and agreement with the conventional monitor stimulation were determined. Results. CSLO recordings showed a high degree of variability. Reduction of laser power output improved the retinal response topography and characteristically modified response variations with each filter. Differences in amplitude size between cSLO and monitor recordings decreased with increasing amplitude levels. The results of repeated measurements showed considerable variation. Conclusion. It is possible to use a cSLO as a stimulator for mfERG recordings. However, a relatively high degree of variability represents a significant limitation of this method. Appropriate reduction of laser power decreases variations and serves to obtain photopic response topographies

Syndromic choroideremia: sublocalization of phenotypes associated with Martin-Probst deafness mental retardation syndrome

PURPOSE: To identify the mutation leading to syndromic choroideremia (CHM) in two families and to define fundus autofluorescence (FAF) in CHM carriers. METHODS: The ophthalmic and clinical phenotype was investigated including FAF, neuropediatric, otorhinolaryngologic, cardiologic, and nephrologic examinations of three male patients (age, 11-46 years) and three female carriers (age, 11-46 years) from two families. Genomic DNA amplification (PCR) of the REP1 gene as well as adjacent loci was used to determine the molecular basis of the phenotype. RESULTS: Analysis of genomic DNA revealed large deletions that asymmetrically flank REP1 in both families, ranging from a minimum size of 6.3 and 8.5 mega base pairs (Mbp) to a maximum size of 9.7 and 14.1 Mbp, respectively. In addition to CHM, patients from these families exhibited mild syndromic features, including mental and motor retardation and low-frequency hearing loss. FAF showed a distinctive pattern characterized by small areas of reduced and increased autofluorescence in all female carriers. CONCLUSIONS: Both CHM families are the first to be described with large deletions that manifest with a mild syndromic phenotype. The location of the deletions indicates that they may allow sublocalization of the syndromic features to the most proximal region of X-linked distal spinal muscular atrophy (DSMAX) and Martin-Probst deafness mental retardation syndrome (MPDMRS). The FAF pattern is specific to CHM carriers and thus will help to identify and differentiate between carriers of other X-linked recessive carrier states such as in X-linked retinitis pigmentosa

Probleme der Bildung und Verwendung des Fonds Wissenschaft und Technik zur Sicherung der wissenschaftlich-technischen Aufgaben der zentralgeleiteten Industriekombinate in der DDR

DB Leipzig(101) - Di 1983 B VD 121, T. 1, 2 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman