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B Wissinger

Publications and source records attributed to B Wissinger.

At least 37 records · Page 2Linked to original sources
PubMed1999

A pedigree of Leber's hereditary optic neuropathy with visual loss in childhood, primarily in girls.

BACKGROUND: Leber's hereditary optic neuropathy (LHON) mostly affects young males. In patients carrying one of the primary mutations the risk to develop LHON is 50% for males and 10% for females. We report a family with predominantly young girls affected. METHODS: In a family with 14 known maternal relatives (11 females, 3 males) 9 patients in 4 generations developed LHON. Eight of the 9 patients were females. Three affected females could be examined and followed. RESULTS: The only affected male showed the typical course of LHON with acute visual loss in both eyes (20/400-20/800) within 6 weeks at 20 years of age. Eight of 9 females developed signs of LHON. In these females acute visual loss occurred at about 10 years of age. Final visual acuity was about 20/200. Central or paracentral scotomata, color vision defects and delayed P100 latencies in the VEP were seen. Ophthalmoscopy showed hyperemic discs in the acute stage and optic atrophy in later stages. Molecular genetic analysis revealed the presence of the mtDNA ND4/np11778 mutation in this family. Specific clinical or additional molecular genetic risk factors could not be detected. CONCLUSION: Families with LHON may show considerable variations of the clinical course and the gender- or age-specific risk. We present a family with a high disease penetrance of 64% and a 2 times higher risk for young females than for males. Furthermore, early visual loss in this family is permanent.

Adult↗
PubMed1999

Leber's hereditary optic neuropathy: clinical and molecular genetic findings in a patient with a new mutation in the ND6 gene.

BACKGROUND: Leber's hereditary optic neuropathy (LHON) is a maternally inherited ocular disease associated with mutations in the mitochondrial DNA (mtDNA). We describe the clinical and molecular genetic findings in a LHON patient and his family with a new mtDNA mutation at np14568 in the ND6 gene. METHODS: Ophthalmological examination was performed in one affected male and two maternal relatives. Direct sequence analysis of the complete mtDNA protein coding region was initiated in the affected patient. Four unaffected maternal relatives also underwent molecular genetic evaluation. RESULTS: Clinical examination of the affected male showed typical features of LHON. In his unaffected mother slight peripapillary microangiopathy was found. Molecular analysis did not show any of the common LHON mutations. A nucleotide exchange was detected at position 14568 replacing a glycine by serine in the ND6 gene. This mutation was the only new mutation found within the entire protein and tRNA coding region of the patient's mitochondrial genome. This novel mutation was also present in four non-affected maternal family members, but absent in 60 other LHON lineages and 175 unrelated controls. CONCLUSION: The new mutation at nucleotide position 14568 lies in the close vicinity of other LHON-related mutations (np14459, np14484, np14498, np14596) within the evolutionarily most conserved region of the ND6 gene. Since no other mutation was detected throughout the mtDNA coding region and the new alteration was excluded in controls, our clinical and molecular genetic findings suggest that the novel point mutation at np14568 is responsible for LHON in this family.

Adolescent↗
PubMed1999

Biochemical but not clinical vitamin A deficiency results from mutations in the gene for retinol binding protein.

BACKGROUND: Two German sisters aged 14 and 17 y were admitted to the Tübingen eye hospital with a history of night blindness. In both siblings, plasma retinol binding protein (RBP) concentrations were below the limit of detection (<0.6 micromol/L) and plasma retinol concentrations were extremely low (0.19 micromol/L). Interestingly, intestinal absorption of retinyl esters was normal. In addition, other factors associated with low retinol concentrations (eg, low plasma transthyretin or zinc concentrations or mutations in the transthyretin gene) were not present. Neither sibling had a history of systemic disease. OBJECTIVE: Our aim was to investigate the cause of the retinol deficiency in these 2 siblings. DESIGN: The 2 siblings and their mother were examined clinically, including administration of the relative-dose-response test, DNA sequencing of the RBP gene, and routine laboratory testing. RESULTS: Genomic DNA sequence analysis revealed 2 point mutations in the RBP gene: a T-to-A substitution at nucleotide 1282 of exon 3 and a G-to-A substitution at nucleotide 1549 of exon 4. These mutations resulted in amino acid substitutions of asparagine for isoleucine at position 41 (Ile41-->Asn) and of aspartate for glycine at position 74 (Gly74-->Asp). Sequence analysis of cloned polymerase chain reaction products spanning exons 3 and 4 showed that these mutations were localized on different alleles. The genetic defect induced severe biochemical vitamin A deficiency but only mild clinical symptoms (night blindness and a modest retinal dystrophy without effects on growth). CONCLUSIONS: We conclude that the cellular supply of vitamin A to target tissues might be bypassed in these siblings via circulating retinyl esters, beta-carotene, or retinoic acid, thereby maintaining the health of peripheral tissues.

Adolescent↗
PubMed1999

Direct visual resolution of gene copy number in the human photopigment gene array.

PURPOSE: To visualize by direct fluorescent in situ hybridization the entire human visual pigment gene array on single X-chromosome fibers and to compare the results with values obtained by other molecular techniques. METHODS: The size of the opsin gene array on the X-chromosome in eight male subjects was investigated by (i) direct visual in situ hybridization (DIRVISH) on elongated DNA fibers: (ii) quantitation of genomic restriction fragments after Southern blot hybridization; (iii) quantitation of restriction fragment length polymorphism after PCR amplification (PCR/RFLP), and (iv) sizing of NotI fragments by pulsed field gel electrophoresis and Southern blot detection. Each male subject's color vision was assessed by Rayleigh matches on a Nagel Type 1 anomaloscope. RESULTS: The number of genes resolved by the DIRVISH protocol, which ranges from 1 to 6, agrees exactly with the gene array sizes obtained in the same male subjects from pulsed field gel electrophoresis, but differs from the estimates derived from the commonly used indirect Southern blot hybridization and PCR/RFLP quantitation methods. In particular, the PCR/RFLP method overestimates the copy number in all but the smallest arrays. CONCLUSIONS: Visualization of the X-chromosome opsin gene array by DIRVISH provides a new, direct method for obtaining exact copy numbers and helps to resolve the controversy about the range and the average visual pigment gene number in the human population in favor of smaller average array sizes.

Blotting, Southern↗
PubMed1999

Phenotype in retinol deficiency due to a hereditary defect in retinol binding protein synthesis.

PURPOSE: To describe the phenotype caused by a retinol deficiency in a family with compound heterozygous missense mutations (Ile41Asn and Gly75Asp) in the gene for serum retinol binding protein (RBP). METHODS: The two affected sisters, 17 (BR) and 13 (MR) years old, were examined clinically and with perimetry, color vision tests, dark adaptometry, rod- and cone-isolated electroretinograms (ERGs), multifocal ERGs, electrooculograms (EOGs), and laboratory tests. RESULTS: There were no complaints besides night vision problems and no history of systemic disease. Visual acuity was reduced to 20/40 (BR) and 20/25 (MR). Anterior segments were normal except for a discrete iris coloboma. Both patients showed a typical "fundus xerophthalmicus," featuring a progressed atrophy of the retinal pigment epithelium. Dark adaptation thresholds were elevated. In the scotopic ERG, only reduced mixed responses were recordable. The photopic ERG was reduced in BR and normal in MR; implicit times were highly (BR) to slightly (MR) elevated. There was no (BR) to little (MR) light reaction in the EOG. All-trans retinol levels were 0.19 microM and 0.18 microM (normal range, 0.7-1.5 microM) for BR and MR, respectively, and did not increase in a dose-response test. RBP was below detection threshold, and retinyl esters were normal. CONCLUSIONS: Both affected siblings had no detectable serum RBP, one sixth of normal retinol levels, and normal retinyl esters. The retinal pigment epithelium was severely affected, but besides acne there were no changes to other organs. This gives evidence for an alternative tissue source of vitamin A, presumably retinyl esters from chylomicron remnants. The normal retinol levels in the tear fluid explain the lack of xerophthalmia. However, considering the role of RBP in the tear fluid and, during development, in the yolk sac there is also evidence that there are organ-specific RBP forms not affected by the genetic defect.

Adolescent↗
PubMed1998

Human rod monochromacy: linkage analysis and mapping of a cone photoreceptor expressed candidate gene on chromosome 2q11.

We have performed linkage analysis in eight families with rod monochromacy, an autosomal recessively inherited condition with complete color blindness. Significant linkage was found with markers located at the pericentromeric region of chromosome 2. A maximum lod score of 5.36 was obtained for marker D2S2333 at theta = 0.00. Mapping of meiotic breakpoints localized the disease gene between markers D2S2187 and D2S2229. Homozygosity for a number of subsequent markers indicating identity by descent was found in two families and provides evidence for a further refinement of the locus proximal to D2S373. This defines an interval of approximately 3 cM covering the ACHM2 locus for rod monochromacy. Radiation hybrid mapping of the CNGA3 gene encoding the alpha-subunit of the cGMP gated cation channel in human cone photoreceptors resulted in a maximum lod score of 16.1 with marker D2S2311 combined with a calculated physical distance of 6.19cR10,000. Screening of the CEPH YAC library and subsequent STS mapping indicated the physical order cen-D2S2222-D2S2175-(D2S2187/D2S2311)-qtel ofmarkers on 2q11 and showed that the CNGA3 gene maps most closely to D2S2187 and D2S2311. These data indicate that the CNGA3 gene maps within the critical interval of the ACHM2 locus for rod monochromacy and thus is a candidate gene for this disease.

Chromosome Breakage↗
PubMed1998

[Diagnostic error in Leber's optic neuropathy. Value of clinical and molecular genetic studies].

BACKGROUND: Leber's hereditary optic neuropathy is associated with point mutations in the mitochondrial DNA (mtDNA) that appear to be pathogenic for this disease. These mutations affect nucleotide positions 3460, 11,778 and 14,484. MATERIALS AND METHODS: We reviewed the clinical and molecular genetic characteristics of 29 visually symptomatic patients with the clinical diagnosis of LHON. RESULTS: Nine patients really suffered from LHON, but in 20 patients other ocular diseases could be proven. Degeneration of the retina and choroid was most common (seven patients), followed by vascular optic disease (six patients). Three patients suffered from tobacco-alcohol amblyopia, two from optic neuritis and two from autosomal dominant optic neuropathy. CONCLUSIONS: The clinical diagnosis of LHON is strengthened by a proven maternal inheritance and clinical signs such as a severe decrease in visual acuity, central or centrocecal scotomas in the perimetry and pseudoedema of the optic disc, followed by optic atrophy. Pathognomonic clinical signs of LHON are twisted vessels and ectatic capillaries in the fundus of these patients and their relatives of the maternal line, i.e., peripapillary microangiopathy. A careful analysis of the patients' pedigrees, anamnesis and the functional and morphological results of the clinical examinations helps to avoid misdiagnosis of the disease. However, the expensive and time-consuming molecular genetic analysis is always necessary to confirm or exclude the diagnosis of LHON.

Adult↗
PubMed1998

Numbers and ratios of X-chromosomal-linked opsin genes.

Quantitative Southern blotting and PCR/RFLP analysis were used to determine the number and ratio of long-wave-sensitive (L-) and mid-wave-sensitive (M-) opsin genes in 25 colour-normal caucasian males. The average observed ratio was 1:2.8 +/- 1.2 for Southern blot analysis and 1:3.0 +/- 1.7 for PCR/RFLP analysis. Thus, the two techniques yielded similar results for the ratio of L- to M-opsin genes (Wilcoxon t-test, P < 0.01). PCR/RFLP analysis of a Sma I polymorphism specific for the most proximal opsin gene suggested an average gene number of 6.0 +/- 2.1, with a range from 4 to 12 in individual subjects. In contrast, Southern blot analysis suggested an average number of 3.8 +/- 1.2, with a range from 2 to 7 (on the assumption that only one L-opsin gene is ever present). Differences between the L- to M-opsin gene ratio and the total gene number in some subjects may result from the presence of multiple L-opsin genes and/or hybrid opsin genes in colour-normal males. An exact determination of the total gene number will require employing other molecular techniques.

Blotting, Southern↗
PubMed1998

Total colourblindness is caused by mutations in the gene encoding the alpha-subunit of the cone photoreceptor cGMP-gated cation channel.

Total colourblindness (OMIM 216900), also referred to as rod monochromacy (RM) or complete achromatopsia, is a rare, autosomal recessive inherited and congenital disorder characterized by photophobia, reduced visual acuity, nystagmus and the complete inability to discriminate between colours. Electroretinographic recordings show that in RM, rod photoreceptor function is normal, whereas cone photoreceptor responses are absent. The locus for RM has been mapped to chromosome 2q11 (ref. 2), however the gene underlying RM has not yet been identified. Recently, a suitable candidate gene, CNGA3, encoding the alpha-subunit of the cone photoreceptor cGMP-gated cation channel, a key component of the phototransduction pathway, has been cloned and assigned to human chromosome 2q11 (refs 3,4). We report the identification of missense mutations in CNGA3 in five families with RM. Homozygous mutations are present in two families, whereas the remaining families show compound heterozygous mutations. In all cases, the segregation pattern of the mutations is consistent with the autosomal recessive inheritance of the disease and all mutations affect amino acids that are highly conserved among cyclic nucleotide gated channels (CNG) in various species. This is the first report of a colour vision disorder caused by defects other than mutations in the cone pigment genes, and implies at least in this instance a common genetic basis for phototransduction in the three different cone photoreceptors of the human retina.

Base Sequence↗
PubMed1998

The role of the peripherin/RDS gene in retinal dystrophies.

Peripherin/RDS is a transmembrane glycoprotein expressed in vertebrate photoreceptors. It is located at the rim of the disc membranes of the photoreceptor outer segments, where it is thought to play an important role in folding and stacking of the discs. Initially, the identification of a mutation in the rds mouse model defined the role of this gene in hereditary retinal dystrophies. To date over 60 different mutations have been reported in human retinal diseases, with most being restricted to single families. A characteristic of mutations in the peripherin/RDS gene is the broad phenotypic spectrum in patients, and the variability in clinical expression, even within families. Thus, genotype-phenotype correlations are difficult and only reliable for a minority of mutations.

Animals↗
PubMed1997

Mutation analysis of the ND6 gene in patients with Lebers hereditary optic neuropathy.

DNA sequence analysis of the gene encoding subunit 6 of the NADH-ubiquinone-oxidoreductase complex (ND6) in human mitochondria was performed in 25 independent patients who suffer from Lebers hereditary optic neuropathy (LHON). In 10 cases the well-known LHON mutation at nucleotide position (np) 14484 was detected. Furthermore, silent substitutions at np14167 and np14527 and missense mutations at np14498, np14564, np14568, and np14582 were found in individual patients. The np14498 and np14568 mutations were found in patients who present a typical clinical picture and course of LHON but lack any of the canonical mtDNA mutations. The np14568 mutation, which replaces a moderately conserved glycine by a serine residue, was observed in a single male patient and subsequently excluded in 175 independent controls. The mutation at np14498, which replaces an evolutionarily highly conserved tyrosine with a cysteine, was found in a multigeneration family with four affected members, the eldest carrying a heteroplasmic mixture of mutated and wildtype mtDNA molecules. None of 170 analyzed control subjects carried this mutation. These findings provide evidence that several allelic ND6 gene mutations may be involved in Lebers hereditary optic neuropathy.

Alleles↗
PubMed1997

Cloning, chromosomal localization and functional expression of the gene encoding the alpha-subunit of the cGMP-gated channel in human cone photoreceptors.

Cyclic nucleotide-gated (CNG) ion channels serve as final targets of signal transduction in vertebrate photoreceptors. While the basic mechanisms of phototransduction are similar in rod and cone photoreceptors, both cell types express distinct sets of components of the transduction pathway. We report here the cloning of the cDNA encoding the alpha-subunit of the cGMP-gated channel of human cone photoreceptors. The open reading frame predicts a polypeptide of 694 amino acid residues with conserved functional parts and amino acid positions typical for the alpha-subunit of CNG-channels. Heterologous expression of the cDNA in Xenopus oocytes gave rise to cGMP-gated channel activity. Antiserum directed against the C-terminus of the bovine cone CNG channel alpha-subunit crossreacted specifically with the heterologously expressed polypeptide and stained cone photoreceptors and weakly also the outer plexiform layer in human retinal sections. Northern blot analysis detected a prominent mRNA species of approximately 3.8 kb in human retina. The entire gene spans approximately 30 kb of genomic sequence and is located on the pericentric band q11.2 of human chromosome 2. The gene is composed of seven exons, with introns located at positions which are preserved with respect to the human rod gene, indicating a common ancestral gene structure. RT-PCR analysis gave no evidence for alternatively spliced transcripts.

Animals↗
PubMed1997

RDS/peripherin gene mutations are frequent causes of central retinal dystrophies.

Patients from 76 independent families with various forms of mostly central retinal dystrophies were screened for mutations in the RDS/peripherin gene by means of SSCP analysis and direct DNA sequencing. Two nonsense mutations (Gln239ter, Tyr285ter), five missense mutations (Arg172Trp, Lys197Glu, Gly208Asp, Trp246Arg, Ser289Leu), and one single base insertion (Gly208insG), heterozygous in all cases, were detected. Only one of these mutations, Arg172Trp, has been reported previously. Cosegregation of the mutation with the disease phenotype could be established in selected families. Other missense mutations were excluded from a panel of 55-75 control subjects. The patients showed remarkable variation in phenotype and disease expression not only between cases with different mutations but also between affected members of the same family. This study indicates that RDS/peripherin mutations are a frequent cause of various types of central retinal dystrophies and that the RDS/peripherin gene exhibits a broad spectrum of allelic mutations. Comparative analysis of known mutations allowed us to hypothesise that the deleterious effect of RDS/peripherin gene mutations is the result of different molecular mechanisms.

Exons↗
PubMed1997

The two human organic cation transporter genes SLC22A1 and SLC22A2 are located on chromosome 6q26.

Polyspecific transporters for organic cations (OCT) belong to a new protein family which also include organic anion transporters. The first human transporters from this family (OCT1, OCT2) have been recently cloned. They translocate small cations like tetraethylammonium, choline and monoamine neurotransmitters and are involved in hepatic and renal cation excretion, respectively. We have localized the OCT1 and OCT2 genes (SLC22A1, SLC22A2) on chromosome 6q26.

Carrier Proteins↗
PubMed1997

Simultaneous detection of multiple point mutations using fluorescence-coupled competitive primer extension.

We report the development of a method for the simultaneous genotyping of several distinct nucleotide positions by means of fluorescence-coupled competitive primer extension. We demonstrate the application of this method for the simultaneous detection of three point mutations in the human mitochondrial genome, at nucleotide positions 3460, 11778 and 14484, which account for about 90% of cases with Leber's hereditary optic neuropathy. mtDNA fragments encompassing these nucleotide positions are initially amplified in a multiplex PCR assay. Genotyping is then carried out by a simultaneous primer extension assay using wild-type-specific (FAM-labeled) and mutant-specific (JOE-labeled) oligonucleotides. Primer extension products are separated on a 6% polyacrylamide/8 M urea gel on a fluorescence DNA sequencer. Patients' genotypes can be derived from the peak color of the different-sized extension products. As little as 10% mutant DNA can be detected in heteroplasmic mixtures of wild-type and mutant mtDNA, a degree that is sufficient for routine clinical practice.

Base Sequence↗
PubMed1996

Analysis of 21 Stargardt's disease families confirms a major locus on chromosome 1p with evidence for non-allelic heterogeneity in a minority of cases.

BACKGROUND: Autosomal recessive Stargardt's disease is a macular degeneration characterised by a juvenile onset and a rapidly progressive course resulting in an atrophic macular area typically surrounded by yellowish retinal flecks. METHOD: The disease locus has previously been assigned to markers from chromosome 1p21-p13 by genetic linkage analysis in eight multiplex Stargardt's disease families. RESULTS: In an extended analysis, the assignment to chromosome 1p was confirmed in the majority of the 21 families with Stargardt's disease who were studied. In addition, a series of recombinant chromosomes further narrowed the Stargardt's disease region to an approximately 3 cM interval between markers at D1S424 and D1S497. CONCLUSION: Multipoint linkage analysis most probably excludes this locus in three of these families suggesting non-allelic heterogeneity with at least one additional minor Stargardt's disease locus.

Chromosomes, Human, Pair 1↗