Biomedical subjects

Wolfgang Berger

Publications and source records attributed to Wolfgang Berger.

At least 19 recordsLinked to original sources

PubMed2007

Glutathione S-transferase genotypes modify lung function decline in the general population: SAPALDIA cohort study.

BACKGROUND: Understanding the environmental and genetic risk factors of accelerated lung function decline in the general population is a first step in a prevention strategy against the worldwide increasing respiratory pathology of chronic obstructive pulmonary disease (COPD). Deficiency in antioxidative and detoxifying Glutathione S-transferase (GST) gene has been associated with poorer lung function in children, smokers and patients with respiratory diseases. In the present study, we assessed whether low activity variants in GST genes are also associated with accelerated lung function decline in the general adult population. METHODS: We examined with multiple regression analysis the association of polymorphisms in GSTM1, GSTT1 and GSTP1 genes with annual decline in FEV1, FVC, and FEF25-75 during 11 years of follow-up in 4686 subjects of the prospective SAPALDIA cohort representative of the Swiss general population. Effect modification by smoking, gender, bronchial hyperresponisveness and age was studied. RESULTS: The associations of GST genotypes with FEV1, FVC, and FEF25-75 were comparable in direction, but most consistent for FEV1. GSTT1 homozygous gene deletion alone or in combination with GSTM1 homozygous gene deletion was associated with excess decline in FEV1 in men, but not women, irrespective of smoking status. The additional mean annual decline in FEV1 in men with GSTT1 and concurrent GSTM1 gene deletion was -8.3 ml/yr (95% confidence interval: -12.6 to -3.9) relative to men without these gene deletions. The GSTT1 effect on the FEV1 decline comparable to the observed difference in FEV1 decline between never and persistent smoking men. Effect modification by gender was statistically significant. CONCLUSION: Our results suggest that genetic GSTT1 deficiency is a prevalent and strong determinant of accelerated lung function decline in the male general population.

Adult↗

PubMed2006

Mutation in the auxiliary calcium-channel subunit CACNA2D4 causes autosomal recessive cone dystrophy.

Retinal signal transmission depends on the activity of high voltage-gated l-type calcium channels in photoreceptor ribbon synapses. We recently identified a truncating frameshift mutation in the Cacna2d4 gene in a spontaneous mouse mutant with profound loss of retinal signaling and an abnormal morphology of ribbon synapses in rods and cones. The Cacna2d4 gene encodes an l-type calcium-channel auxiliary subunit of the alpha (2) delta type. Mutations in its human orthologue, CACNA2D4, were not yet known to be associated with a disease. We performed mutation analyses of 34 patients who received an initial diagnosis of night blindness, and, in two affected siblings, we detected a homozygous nucleotide substitution (c.2406C-->A) in CACNA2D4. The mutation introduces a premature stop codon that truncates one-third of the corresponding open reading frame. Both patients share symptoms of slowly progressing cone dystrophy. These findings represent the first report of a mutation in the human CACNA2D4 gene and define a novel gene defect that causes autosomal recessive cone dystrophy.

Adult↗

PubMed2006

Development of a genotyping microarray for Usher syndrome.

BACKGROUND: Usher syndrome, a combination of retinitis pigmentosa (RP) and sensorineural hearing loss with or without vestibular dysfunction, displays a high degree of clinical and genetic heterogeneity. Three clinical subtypes can be distinguished, based on the age of onset and severity of the hearing impairment, and the presence or absence of vestibular abnormalities. Thus far, eight genes have been implicated in the syndrome, together comprising 347 protein-coding exons. METHODS: To improve DNA diagnostics for patients with Usher syndrome, we developed a genotyping microarray based on the arrayed primer extension (APEX) method. Allele-specific oligonucleotides corresponding to all 298 Usher syndrome-associated sequence variants known to date, 76 of which are novel, were arrayed. RESULTS: Approximately half of these variants were validated using original patient DNAs, which yielded an accuracy of >98%. The efficiency of the Usher genotyping microarray was tested using DNAs from 370 unrelated European and American patients with Usher syndrome. Sequence variants were identified in 64/140 (46%) patients with Usher syndrome type I, 45/189 (24%) patients with Usher syndrome type II, 6/21 (29%) patients with Usher syndrome type III and 6/20 (30%) patients with atypical Usher syndrome. The chip also identified two novel sequence variants, c.400C>T (p.R134X) in PCDH15 and c.1606T>C (p.C536S) in USH2A. CONCLUSION: The Usher genotyping microarray is a versatile and affordable screening tool for Usher syndrome. Its efficiency will improve with the addition of novel sequence variants with minimal extra costs, making it a very useful first-pass screening tool.

DNA↗

PubMed2006

Mutations in CABP4, the gene encoding the Ca2+-binding protein 4, cause autosomal recessive night blindness.

Mutations in genes encoding either components of the phototransduction cascade or proteins presumably involved in signaling from photoreceptors to adjacent second-order neurons have been shown to cause congenital stationary night blindness (CSNB). Sequence alterations in CACNA1F lead to the incomplete type of CSNB (CSNB2), which can be distinguished by standard electroretinography (ERG). CSNB2 is associated with a reduced rod b-wave, a substantially reduced cone a-wave, and a reduced 30-Hz flicker ERG response. CACNA1F encodes the alpha 1-subunit of an L-type Ca2+ channel (Cav1.4 alpha ), which is specific to photoreceptors and is present at high density in the synaptic terminals. Ten of our patients with CSNB2 showed no mutation in CACNA1F. To identify the disease-causing mutations, we used a candidate-gene approach. CABP4, a member of the calcium-binding protein (CABP) family, is located in photoreceptor synaptic terminals and is directly associated with the C-terminal domain of the Cav1.4 alpha . Mice lacking either Cabp4 or Cav1.4 alpha display a CSNB2-like phenotype. Here, we report for the first time that mutations in CABP4 lead to autosomal recessive CSNB. Our studies revealed homozygous and compound heterozygous mutations in two families. We also show that these mutations reduce the transcript levels to 30%-40% of those in controls. This suggests that the reduced amount of CABP4 is the reason for the signaling defect in these patients.

Adolescent↗

PubMed2006

Degenerative aortic valve stenosis, but not coronary disease, is associated with shorter telomere length in the elderly.

OBJECTIVE: The mechanisms responsible for the age-related increase in the incidence of calcific aortic valve stenosis (CAS) are unclear but may include telomere-driven cellular senescence. Because telomere length varies widely among individuals of the same age, we hypothesized that patients with shorter telomeres would be prone to develop CAS late in life. METHODS AND RESULTS: Mean telomere length was measured in leukocytes from a cohort of 193 patients > or =70 years of age with and without CAS. Pilot experiments performed in 30 patients with CAS and controls pair-matched for age, sex, and presence or absence of coronary disease demonstrated significantly shorter telomeres in the CAS group both by Southern blot hybridization (5.75+/-0.55 kbp versus 6.27+/-0.7 kbp, P=0.0023) and by a quantitative polymerase chain reaction-based technique (relative telomere length 0.88+/-0.19 versus 1.0+/-0.19, P=0.01). This finding was then confirmed in the whole cohort (CAS n=64, controls n=129, relative telomere length=0.86+/-0.16 versus 0.94+/-0.12, P=0.0003). Both groups were comparable for potential confounding characteristics. Subgroup analysis according to the presence or absence of coronary disease demonstrated no association of this disorder with telomere length. CONCLUSIONS: In the elderly, calcific aortic stenosis, but not coronary disease, is associated with shorter leukocyte telomere length.

Aged↗

PubMed2006

Identification of the genetic defect in the original Wagner syndrome family.

PURPOSE: The aim of the present study was to determine the genetic defect in Wagner syndrome, a rare disorder belonging to the group of hereditary vitreoretinal degenerations. This disease has been genetically mapped to chromosome 5q14.3. METHODS: Molecular analysis was performed in the progeny of the original pedigree described by Wagner in 1938. We searched for pathogenic mutations and their effects in two candidate genes, CSPG2 and EDIL3, which locate to the critical chromosomal interval. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis was used to investigate potential splice defects of CSPG2 transcripts. RESULTS: While no alterations were detected in the exons of EDIL3, several changes were identified in the CSPG2 gene. Only one of the novel changes, a heterozygous G to A substitution of the first nucleotide in intron 8, cosegregates with the disease phenotype. This change disrupts the highly conserved splice donor sequence. In blood cells of an index patient, we found CSPG2 transcripts with normally spliced exon 8/9 junction but also two additional CSPG2 transcripts, which were not detected in the control. One lacks the entire exon 8, while the other is missing only the last 21 bp of exon 8. CONCLUSIONS: CSPG2 encodes versican, a large proteoglycan, which is an extracellular matrix component of the human vitreous and participates in the formation of the vitreous gel. The splice site mutation described here may lead to a complete lack of exon 8 in CSPG2 transcripts, which shortens the predicted protein by 1754 amino acids and leads to severe reduction of glycosaminoglycan attachment sites.

Adenine↗

PubMed2006

Identification and in silico analyses of novel TGFBR1 and TGFBR2 mutations in Marfan syndrome-related disorders.

Very recently, heterozygous mutations in the genes encoding transforming growth factor beta receptors I (TGFBR1) and II (TGFBR2) have been reported in Loeys-Dietz aortic aneurysm syndrome (LDS). In addition, dominant TGFBR2 mutations have been identified in Marfan syndrome type 2 (MFS2) and familial thoracic aortic aneurysms and dissections (TAAD). In the past, mutations of these genes were associated with atherosclerosis and several human cancers. Here, we report a total of nine novel and one known heterozygous sequence variants in the TGFBR1 and TGFBR2 genes in nine of 70 unrelated individuals with MFS-like phenotypes who previously tested negative for mutations in the gene encoding the extracellular matrix protein fibrillin-1 (FBN1). To assess the pathogenic impact of these sequence variants, in silico analyses were performed by the PolyPhen, SIFT, and Fold-X algorithms and by means of a 3D homology model of the TGFBR2 kinase domain. Our results showed that in all but one of the patients the pathogenic effect of at least one sequence variant is highly probable (c.722C > T, c.799A > C, and c.1460G > A in TGFBR1 and c.773T > G, c.1106G > T, c.1159G > A, c.1181G > A, and c.1561T > C in TGFBR2). These deleterious alleles occurred de novo or segregated with the disease in the families, indicating a causative association between the sequence variants and clinical phenotypes. Since TGFBR2 mutations found in patients with MFS-related disorders cannot be distinguished from heterozygous TGFBR2 mutations reported in tumor samples, we emphasize the importance of segregation analysis in affected families. In order to be able to find the mutation that is indeed responsible for a MFS-related phenotype, we also propose that genetic testing for sequence alterations in TGFBR1 and TGFBR2 should be complemented by mutation screening of the FBN1 gene.

Activin Receptors, Type I↗

PubMed2006

Nyctalopin is essential for synaptic transmission in the cone dominated zebrafish retina.

The first synapse in the vertebrate visual system is the photoreceptor synapse between rod and cone photoreceptors and the second-order bipolar cells. Although mutations in the nyctalopin gene (NYX) in humans lead to congenital stationary night blindness (CSNB1), affecting synaptic transmission between both types of photoreceptors and ON-bipolar cells, the function of nyctalopin in cone-dominant animal models has not been studied. Because the larval zebrafish retina is cone-dominant, we isolated the zebrafish nyx ortholog and raised a polyclonal antibody against the protein. Nyctalopin is expressed postsynaptically in both synaptic layers of the retina. Functional disruption via morpholino antisense injection leads to characteristic defects in the electroretinogram and defects in visual contrast sensitivity. We therefore demonstrated that nyctalopin plays a similar role in retinal synapse function in the cone pathway as in the rod pathway, thereby creating a genetic model for CSNB1 and its effects on cone vision.

Animals↗

PubMed2006

Different amino acid substitutions at the same position in rhodopsin lead to distinct phenotypes.

PURPOSE: Identification of a novel rhodopsin mutation in a family with retinitis pigmentosa and comparison of the clinical phenotype to a known mutation at the same amino acid position. METHODS: Screening for mutations in rhodopsin was performed in 78 patients with retinitis pigmentosa. All exons and flanking intronic regions were amplified by PCR, sequenced, and compared to the reference sequence derived from the National Center for Biotechnology Information (NCBI, Bethesda, MD) database. Patients were characterized clinically according to the results of best corrected visual acuity testing (BCVA), slit lamp examination (SLE), funduscopy, Goldmann perimetry (GP), dark adaptometry (DA), and electroretinography (ERG). Structural analyses of the rhodopsin protein were performed with the Swiss-Pdb Viewer program available on-line (http://www.expasy.org.spdvbv/ provided in the public domain by Swiss Institute of Bioinformatics, Geneva, Switzerland). RESULTS: A novel rhodopsin mutation (Gly90Val) was identified in a Swiss family of three generations. The pedigree indicated autosomal dominant inheritance. No additional mutation was found in this family in other autosomal dominant genes. The BCVA of affected family members ranged from 20/25 to 20/20. Fundus examination showed fine pigment mottling in patients of the third generation and well-defined bone spicules in patients of the second generation. GP showed concentric constriction. DA demonstrated monophasic cone adaptation only. ERG revealed severely reduced rod and cone signals. The clinical picture is compatible with retinitis pigmentosa. A previously reported amino acid substitution at the same position in rhodopsin leads to a phenotype resembling night blindness in mutation carriers, whereas patients reported in the current study showed the classic retinitis pigmentosa phenotype. The effect of different amino acid substitutions on the three-dimensional structure of rhodopsin was analyzed by homology modeling. Distinct distortions of position 90 (shifts in amino acids 112 and 113) and additional hydrogen bonds were found. CONCLUSIONS: Different amino acid substitutions at position 90 of rhodopsin can lead to night blindness or retinitis pigmentosa. The data suggest that the property of the substituted amino acid distinguishes between the phenotypes.

Adult↗

PubMed2006

Structural and functional abnormalities of retinal ribbon synapses due to Cacna2d4 mutation.

PURPOSE: In a spontaneous mutant substrain of C57BL/10 mice, severely affected retinal ribbon-type synapses have been described. The retinopathy was accompanied by a substantial loss in the activities of the second-order neurons. Rod photoreceptor responses were maintained with reduced amplitude, whereas cone activities were absent. This study was conducted to identify the genetic defect underlying this hitherto unknown autosomal recessive cone-rod dysfunction. METHODS: Genome-wide linkage analysis and screening of positional candidate genes were used to identify the causative mutation. Tissue-specific transcriptional activity of the defective gene was determined by Northern blot analysis and RT-PCR approaches. The number of cone photoreceptors was estimated by immunohistochemistry. RESULTS: The mutation was localized to a 275-kb region of chromosome 6. Within this candidate interval, a homozygous frameshift mutation (c.2367insC) was identified in the Cacna2d4 gene of affected animals. This gene codes for an L-type calcium channel auxiliary subunit of the alpha2delta type. The mutation introduces a premature stop codon that truncates one third of the predicted Cacna2d4 protein. A severe reduction in Cacna2d4 transcript levels observed in mutant retinas probably results in the lack of Cacna2d4 protein. The mutation leads to significant loss of rods, whereas the number of cone cells remains unaffected until 6 weeks of age. CONCLUSIONS: The Cacna2d4 mutation underlies a novel channelopathy leading to cone-rod dysfunction in the visual system of mice and provides a new candidate gene for human retinal disorders including night blindness, retinitis pigmentosa, and cone-rod dystrophies.

Amino Acid Sequence↗

PubMed2005

Voltage-dependent ion channels in the mouse RPE: comparison with Norrie disease mice.

We studied electrophysiological properties of cultured retinal pigment epithelial (RPE) cells from mouse and a mouse model for Norrie disease. Wild-type RPE cells revealed the expression of ion channels known from other species: delayed-rectifier K(+) channels composed of Kv1.3 subunits, inward rectifier K(+) channels, Ca(V)1.3 L-type Ca(2+) channels and outwardly rectifying Cl(-) channels. Expression pattern and the ion channel characteristics current density, blocker sensitivity, kinetics and voltage-dependence were compared in cells from wild-type and Norrie mice. Although no significant differences were observed, our study provides a base for future studies on ion channel function and dysfunction in transgenic mouse models.

Animals↗

PubMed2005

Mice null for Frizzled4 (Fzd4-/-) are infertile and exhibit impaired corpora lutea formation and function.

Previous studies showed that transcripts encoding specific Wnt ligands and Frizzled receptors including Wnt4, Frizzled1 (Fzd1), and Frizzled4 (Fzd4) were expressed in a cell-specific manner in the adult mouse ovary. Overlapping expression of Wnt4 and Fzd4 mRNA in small follicles and corpora lutea led us to hypothesize that the infertility of mice null for Fzd4 (Fzd4-/-) might involve impaired follicular growth or corpus luteum formation. Analyses at defined stages of reproductive function indicate that immature Fzd4-/- mouse ovaries contain follicles at many stages of development and respond to exogenous hormone treatments in a manner similar to their wild-type littermates, indicating that the processes controlling follicular development and follicular cell responses to gonadotropins are intact. Adult Fzd4-/- mice also exhibit normal mating behavior and ovulate, indicating that endocrine events controlling these processes occur. However, Fzd4-/- mice fail to become pregnant and do not produce offspring. Histological and functional analyses of ovaries from timed mating pairs at Days 1.5-7.5 postcoitus (p.c.) indicate that the corpora lutea of the Fzd4-/- mice do not develop normally. Expression of luteal cell-specific mRNAs (Lhcgr, Prlr, Cyp11a1 and Sfrp4) is reduced, luteal cell morphology is altered, and markers of angiogenesis and vascular formation (Efnb1, Efnb2, Ephb4, Vegfa, Vegfc) are low in the Fzd4-/- mice. Although a recently identified, high-affinity FZD4 ligand Norrin (Norrie disease pseudoglioma homolog) is expressed in the ovary, adult Ndph-/- mice contain functional corpora lutea and do not phenocopy Fzd4-/- mice. Thus, Fzd4 appears to impact the formation of the corpus luteum by mechanisms that more closely phenocopy Prlr null mice.

Animals↗

PubMed2005

A new and a reclassified ICF patient without mutations in DNMT3B and its interacting proteins SUMO-1 and UBC9.

The ICF syndrome (immunodeficiency, centromeric instability, facial anomalies) (OMIM#242860) is a rare autosomal, recessively inherited disorder. Another rare condition, ischiadic hypoplasia, renal dysgenesis, immunodeficiency, and polydactyly (IHRDIP, OMIM#243340), displays features that resemble those of the ICF syndrome. Due to the overlapping symptoms in both syndromes, we asked whether a shared underlying molecular defect exists. Two patients, each with the clinical characteristics of one of these syndromes, were subjected to conventional cytogenetic analysis and the determination of the methylation state of satellite II DNA. We found that both displayed the two hallmark features of the ICF syndrome, namely hypomethylation and centromeric instability of chromosomes 1 and 16. Therefore, we reclassified the patient previously diagnosed with the IHRDIP syndrome as an ICF patient. Since the majority of ICF patients are carriers of mutations in the methytransferase gene DNMT3B, we determined the sequence of its coding, splice site, and putative promoter region and analyzed its transcripts in both patients, without detecting any alterations. Similarly, the coding region of two DNMT3B-interacting proteins, SUMO-1 and UBC9, did not reveal mutations. With this study, the published number of patients that lack mutations in DNMT3B coding region increases to almost 40% of all ICF patients reported. It is, therefore, implied that a significant subset of ICF patients will have a yet unknown, alternative alteration, which may include the involvement of DNMT3B-interacting factors or aberrations of an independent pathway.

Abnormalities, Multiple↗

PubMed2005

Novel mutations in CACNA1F and NYX in Dutch families with X-linked congenital stationary night blindness.

PURPOSE: To describe the clinical features and genetic analysis of eight X-linked congenital stationary night blindness (XLCSNB) Dutch patients. METHODS: Electroretinogram (ERG) measurements were assessed in Dutch patients. Molecular genetic testing by denaturing high performance liquid chromatography (DHPLC), single stranded conformation polymorphism (SSCP) analysis, and direct sequencing of the CACNA1F and NYX genes were performed in the patients possessing a negative Schubert Bornschein ERG. RESULTS: Molecular genetic testing of CACNA1F and NYX revealed three novel and two known CACNA1F sequence variants as well as two novel sequence alterations in the NYX gene. While one of the CACNA1F sequence variants (5756G>A, R1919H) has been previously described as a common polymorphism in Japanese families, we did not found this transition in 100 European control alleles. CONCLUSIONS: In a pool of eight diagnosed XLCSNB patients, five showed a sequence variation in the CACNA1F and two in the NYX gene. In only one of the eight patients no sequence alteration could be detected. This might be explained by a mutation in other, as yet unidentified coding or regulatory sequences of NYX or CACNA1F or additional genes.

Adult↗

PubMed2005

Ectopic norrin induces growth of ocular capillaries and restores normal retinal angiogenesis in Norrie disease mutant mice.

Norrie disease is an X-linked retinal dysplasia that presents with congenital blindness, sensorineural deafness, and mental retardation. Norrin, the protein product of the Norrie disease gene (NDP), is a secreted protein of unknown biochemical function. Norrie disease (Ndp(y/-)) mutant mice that are deficient in norrin develop blindness, show a distinct failure in retinal angiogenesis, and completely lack the deep capillary layers of the retina. We show here that the transgenic expression of ectopic norrin under control of a lens-specific promoter restores the formation of a normal retinal vascular network in Ndp(y/-) mutant mice. The improvement in structure correlates with restoration of neuronal function in the retina. In addition, lenses of transgenic mice with ectopic expression of norrin show significantly more capillaries in the hyaloid vasculature that surrounds the lens during development. In vitro, lenses of transgenic mice in coculture with microvascular endothelial cells induce proliferation of the cells. Transgenic mice with ectopic expression of norrin show more bromodeoxyuridine-labeled retinal progenitor cells at embryonic day 14.5 and thicker retinas at postnatal life than wild-type littermates, indicating a putative direct neurotrophic effect of norrin. These data provide direct evidence that norrin induces growth of ocular capillaries and that pharmacologic modulation of norrin might be used for treatment of the vascular abnormalities associated with Norrie disease or other vascular disorders of the retina.

Animals↗

PubMed2005

Fetal loss in homozygous mutant Norrie disease mice: a new role of Norrin in reproduction.

Mutations in the Norrie disease pseudoglioma gene (NDP) are known to cause X-linked recessive Norrie disease. In addition, NDP mutations have been found in other vasoproliferative retinopathies such as familial exudative vitreoretinopathy, retinopathy of prematurity, and Coats disease, suggesting a role for Norrin in vascular development. Here we report that female mice homozygous for the Norrie disease pseudoglioma homolog (Ndph) knockout allele exhibit almost complete infertility, while heterozygous females and hemizygous males are fertile. Histological examinations and RNA in situ hybridization analyses revealed defects in vascular development and decidualization in pregnant Ndph-/- females from embryonic day 7 (E7) onwards, resulting in embryonic loss. Using RT-PCR analyses we also demonstrate, for the first time, the expression of Ndph in mouse uteri and deciduae as well as the expression of NDP in human placenta. Taken together, these data provide strong evidence for Norrin playing an important role in female reproductive tissues.

Animals↗

PubMed2005

Role of the Norrie disease pseudoglioma gene in sprouting angiogenesis during development of the retinal vasculature.

PURPOSE: To characterize developmental defects and the time course of Norrie disease in retinal and hyaloid vasculature during retinal development and to identify underlying molecular angiogenic pathways that may be affected in Norrie disease, exudative vitreoretinopathy, retinopathy of prematurity, and Coats' disease. METHODS: Norrie disease pseudoglioma homologue (Ndph)-knockout mice were studied during retinal development at early postnatal (p) stages (p5, p10, p15, and p21). Histologic techniques, quantitative RT-PCR, ELISA, and Western blot analyses provided molecular data, and scanning laser ophthalmoscopy (SLO) angiography and electroretinography (ERG) were used to obtain in vivo data. RESULTS: The data showed that regression of the hyaloid vasculature of Ndph-knockout mice occurred but was drastically delayed. The development of the superficial retinal vasculature was strongly delayed, whereas the deep retinal vasculature did not form because of the blockage of vessel outgrowth into the deep retinal layers. Subsequently, microaneurysm-like lesions formed. Several angiogenic factors were differentially transcribed during retinal development. Increased levels of hypoxia inducible factor-1alpha (HIF1alpha) and VEGFA, as well as a characteristic ERG pattern, confirmed hypoxic conditions in the inner retina of the Ndph-knockout mouse. CONCLUSIONS: These data provide evidence for a crucial role of Norrin in hyaloid vessel regression and in sprouting angiogenesis during retinal vascular development, especially in the development of the deep retinal capillary networks. They also suggest an early and a late phase of Norrie disease and may provide an explanation for similar phenotypic features of allelic retinal diseases in mice and patients as secondary consequences of pathologic hypoxia.

Animals↗

PubMed2005

Mutations in GRM6 cause autosomal recessive congenital stationary night blindness with a distinctive scotopic 15-Hz flicker electroretinogram.

PURPOSE: Congenital stationary night blindness (CSNB) is a group of nonprogressive retinal disorders characterized by impaired night vision that occurs in autosomal dominant, autosomal recessive, or X-linked forms. Autosomal recessive (ar)CSNB seems to be very rare. Mice lacking the metabotropic glutamate receptor 6 (Grm6) have a defect in signal transmission from the photoreceptors to ON-bipolar cells. In the current study, the human orthologue (GRM6) was screened as a likely candidate for arCSNB. METHODS: arCSNB individuals of five families were screened for mutations in GRM6. Subsequently, they were examined with standard and 15-Hz flicker electroretinography (ERG). These recordings were compared with those of patients with X-linked CSNB1. RESULTS: Affected individuals in three of five families carried either compound heterozygous or homozygous mutations in GRM6. Strikingly, all of them displayed a distinctive abnormality of the rod pathway signals on scotopic 15-Hz flicker ERG. CONCLUSIONS: The novel profile identified in this study suggests the existence of more than two rod pathways. The distinctive ERG feature was not observed in patients with X-linked CSNB1 and additional affected individuals with unknown molecular defect. These observations will help to discriminate autosomal recessive from X-linked recessive cases by ERG and molecular genetic analysis.

Adolescent↗