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  • 1
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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 α-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 α-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 α-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 ∼3.8 kb in human retina. The entire gene spans ∼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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Higher plants contain the largest mitochondrial genomes found so far. Several factors contribute to this expansion in size, notably integrated plastid and nuclear sequences; numerous repeats, some of which are active in recombination and sequence rearrangements; introns of more than 3 400 nucleotides and several genes unique to plant mitochondrial DNA. Genes are transcribed into mono and polycistronic mRNAs and translated by the standard genetic code. However, mRNAs are altered from the DNA encoded sequence by RNA editing with mostly cytidine to uridine and occasionally uridine to cytidine transitions. Edited mRNAs specify different polypeptides than those predicted by open reading frames in the DNA. Partially edited mRNA molecules raise the question of which proteins are actually synthesized. RNA editing of mitochondrial transcripts appears to occur in all higher plants and may date back to the common ancestors of modern plants.
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  • 3
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  · 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.
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  • 4
    ISSN: 1432-0983
    Keywords: RNA editing ; rRNAs ; atpA ; cytb ; orfB ; Plant mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To investigate whether RNA editing in plant mitochondria modifies structural RNAs as well as protein-coding RNAs we compared the genomic-encoded information with the respective transcripts of several genes in Oenothera. The genes analysed are the 5S, 18S and 26 S rRNAs, the alpha-subunit of ATPase (atpA), cytochrome b (cytb), orfB, which is located upstream of cytochrome oxidase subunit III, and the respective leader, trailer and spacer sequences. All open reading frames were found to be edited to some degree. The atpA coding region has the least edited mRNA in Oenothera mitochondria, with only four nucleotides altered in the 1533 nucleotide open reading frame. From this analysis we conclude that frequent RNA editing is indicative of functional protein coding regions in plant mitochondria. The extensive editing in orfB, for example, suggests that this orf codes for a mitochondrial protein. No RNA editing event was found in the 5S rRNA or in the 1824 nucleotides analysed of the 18S rRNA, but two nucleotides were found to be altered in the 1970 nucleotides compared for the 26S rRNA. One nucleotide alteration has changed C to U, the other in reverse U to C. However, only one of five cDNA clones covering this region shows the modifications, similar to many silent editing events in open reading frames. RNA editing in the structural RNAs thus does not seem to be essential for their function in the mitochondrial ribosome.
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  • 5
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] 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. ...
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  • 6
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] We identified three consanguineous Austrian kindreds with 15 members affected by autosomal recessive childhood-onset severe retinal dystrophy, a genetically heterogeneous group of disorders characterized by degeneration of the photoreceptor cells. A whole-genome scan by microarray analysis of ...
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  • 7
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] X-linked congenital stationary night blindness (XLCSNB) is characterized by impaired scotopic vision with associated ocular symptoms such as myopia, hyperopia, nystagmus and reduced visual acuity. Genetic mapping in families with XLCSNB revealed two different loci on the proximal short arm of the X ...
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  • 8
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Autosomal dominant optic atrophy (ADOA) is the most prevalent hereditary optic neuropathy resulting in progressive loss of visual acuity, centrocoecal scotoma and bilateral temporal atrophy of the optic nerve with an onset within the first two decades of life. The predominant locus for this ...
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 18 (1990), S. 371-375 
    ISSN: 1432-0983
    Keywords: Plant mitochondria ; RNA editing ; Cytochrome oxidase subunit II ; Partial editing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Analysis of cDNA clones covering the entire coding region of cytochrome oxidase subunit II in Oenothera mitochondria reveals 24 potential editing sites: 23 C to U transitions and one U to C conversion. One editing event is observed outside the open reading frame in the 3′ non-coding region. Thirteen editing sites are found altered in all cDNA clones, whereas the other eleven sites are only edited in some of the cDNA clones. These differentially edited sites occur most frequently at silent codon positions or in triplets at non-conserved amino acids.
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  • 10
    ISSN: 1433-0423
    Keywords: Key words Leber hereditary optic neuropathy • LHON • Mitochondrial DNA • mtDNA • Peripapillary microangiopathy • Point mutation ; Schlüsselwörter Lebersche Optikusneuropathie • LHON • mitochondriale DNA • mtDNA • peripapilläre Mikroangiopathie • Punktmutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Fragestellung: Die klinische Verdachtsdiagnose Lebersche Optikusneuropathie (LHON) kann durch molekulargenetische Untersuchungen gesichert werden. LHON wird assoziiert mit dem Auftreten von Punktmutationen in der mitochondrialen DNA (mtDNA), als sicher gilt die pathogenetische Bedeutung eines Basenaustausches an den Positionen 3460, 11 778 und 14 484 der Nukleotidabfolge. Patienten und Methoden: Wir untersuchten 29 Patienten, die in den letzten 3 Jahren (1995–1997) mit der klinischen Verdachtsdiagnose Lebersche Optikusneuropathie überwiesen wurden. Ergebnisse: In 9 Fällen konnte die primäre Verdachtsdiagnose LHON klinisch und molekulargenetisch bestätigt werden, während sich 20 Patienten molekulargenetisch negativ für LHON zeigten und in 7 Fällen eine degenerative Netzhaut- oder Aderhauterkrankung, in 6 Fällen einen vaskulären Optikusprozeß aufwiesen. 3 Patienten hatten eine Tabak-Alkohol-Amblyopie, 2 eine beidseitige Neuritis nervi optici und 2 eine dominant erbliche Optikusatrophie. Schlußfolgerung: Die klinische Verdachtsdiagnose Lebersche Optikusneuropathie stützt sich auf einen meist beidseitigen Visusverlust, den Nachweis eines Zentral- oder Zentrozaekalskotoms im Gesichtsfeld und auf ein Pseudoödem der Papille, das nach Wochen in eine Optikusatrophie übergeht. Pathognomonisch für LHON ist die peripapilläre Mikroangiopathie, die aber während des Krankheitsverlaufs verschwindet. Eine positive Familienanamnese (weitere Erkrankte in der maternalen Linie) erhärtet den Verdacht zusätzlich. Die Fehleranalyse der klinischen Diagnostik zeigte, daß die Beachtung zusätzlicher makularer Veränderungen, die korrekte Interpretation der Gesichtsfeldbefunde, die Berücksichtigung des für LHON typischen klinischen Befundes einer peripapillären Mikroangiopathie und der Nachweis eines maternalen Erbgangs anhand einer Stammbaumanalyse dazu beitragen, eine Fehldiagnose LHON zu vermeiden.
    Notes: 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.
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