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A Gehrig

Publications and source records attributed to A Gehrig.

18 recordsLinked to original sources
PubMed2006

The role of caspases in photoreceptor cell death of the retinoschisin-deficient mouse.

Early schisis cavities in the retinal bipolar cell layer accompanied by progressive loss of cone and rod photoreceptor cells are the hallmark of the retinoschisin-deficient (Rs1h(-/Y)) murine retina. With this study we aimed at elucidating the molecular events underlying the photoreceptor cell death in this established murine model of X-linked juvenile retinoschisis. We show that photoreceptor degeneration in the Rs1h(-/Y) mouse is due to apoptotic events peaking around postnatal day 18. Cell death is accompanied by increased expression of initiator and inflammatory caspases but not by downstream effector caspases. The strong induction of caspase-1 (Casp1) prompted us to explore its involvement in the apoptotic process. We therefore generated double knock-out mice deficient for both retinoschisin and Casp1. No direct influence of the Casp1 genotype on apoptosis could be identified although striking differences in the overall number of resident microglia were observed independent of the Rs1h genotype.

Animals↗
PubMed2004

PTEN mutations do not cause nuclear beta-catenin accumulation in endometrial carcinomas.

PTEN: and beta-catenin mutations constitute the predominant genetic alterations in endometrioid carcinomas of the endometrium. PTEN encodes a dual-specificity phosphatase with lipid phosphatase and protein tyrosine phosphatase activities that regulate both apoptosis and interactions with the extracellular matrix. Recent studies have associated PTEN mutations with tumorigenesis of prostate carcinoma via the Wnt signaling pathway, leading to nuclear beta-catenin accumulation. To elucidate the potential interaction of PTEN and beta-catenin in endometrial cancer, we performed mutation analyses of the entire PTEN gene and of exon 3 of the beta-catenin gene that is most frequently targeted by mutations. A total of 82 endometrial carcinomas comprising 62 type I endometrioid carcinomas and 20 type II high-grade carcinomas were investigated. In addition in a subset of 22 carcinomas, the intracellular beta-catenin distribution was analyzed by immunohistochemistry. Overall, 20 (24.4%) of 82 tumors revealed mutations in the PTEN gene, and 16 (19.5%) of 82, in the beta-catenin gene. Six tumors (7.3%) showed mutations in both the PTEN and beta-catenin gene. Mutations were mainly detected in endometrioid carcinomas of the endometrium. As expected, a striking nuclear accumulation of beta-catenin could be shown in tumors with beta-catenin mutations. In the vast majority of tumors with PTEN mutations, a regular staining pattern of the cytoplasmic and membranous compartments was found. We therefore conclude that, in contrast to prostate cancer, mutations in the PTEN gene seem not to affect cellular distribution of the beta-catenin protein in endometrial carcinomas.

Carcinoma, Endometrioid↗
PubMed2004

Identifying differentially expressed genes in the mammalian retina and the retinal pigment epithelium by suppression subtractive hybridization.

Retina and retinal pigment epithelium (RPE) cells are of neuroectodermal origin with highly specialized functions in light perception. Identification and characterization of genes differentially expressed in these cells will greatly aid our understanding of their functional roles in retinal biology. As a source enriched for gene transcripts from the retina/RPE, we generated a human retina and a bovine RPE cDNA library applying the PCR-based technique of suppression subtractive hybridization (SSH). Sequencing of 1,080 retina and 2,350 RPE SSH clones resulted in the identification of 321 and 343 non-redundant human transcripts, respectively. Of these, only 27 genes were in common between the two cDNA libraries. One transcript expressed exclusively in retina and RPE is the novel gene C4orf11 which is comprised of four exons on chromosome 4q21.2. We report the full-length cloning of two isoforms of C4orf11, 919 bp and 857 bp in length, both of which contain four identical open reading frames (ORFs). While ORFs 1 to 3 show no homologies to known proteins or protein domains, ORF4 reveals 50% sequence identity to RPE-spondin, a hypothetical protein on 8q13.3 with unknown function. We demonstrate that both the retina and the RPE SSH cDNA libraries are excellent resources for identifying known and novel genes exclusively or abundantly expressed in the retina/RPE complex. In combination with other approaches such as microarray analysis or serial analysis of gene expression (SAGE), the availability of highly sensitive and specific SSH cDNA libraries will facilitate the comprehensive description of the retina/RPE transcriptome.

Amino Acid Sequence↗
PubMed2000

Mutations in the VMD2 gene are associated with juvenile-onset vitelliform macular dystrophy (Best disease) and adult vitelliform macular dystrophy but not age-related macular degeneration.

Recently, the VMD2 gene has been identified as the causative gene in juvenile-onset vitelliform macular dystrophy (Best disease), a central retinopathy primarily characterised by an impaired function of the retinal pigment epithelium. In this study we have further characterised the spectrum of VMD2 mutations in a series of 41 unrelated Best disease patients. Furthermore we expanded our analysis to include 32 unrelated patients with adult vitelliform macular dystrophy (AVMD) and 200 patients with age-related macular degeneration (AMD). Both AVMD and AMD share some phenotypic features with Best disease such as abnormal subretinal accumulation of lipofuscin material, progressive geographic atrophy and choroidal neovascularisation, and may be the consequence of a common pathogenic mechanism. In total, we have identified 23 distinct disease-associated mutations in Best disease and four different mutations in AVMD. Two of the mutations found in the AVMD patients were also seen in Best disease suggesting a considerable overlap in the aetiology of these two disorders. There were no mutations found in the AMD group. In addition, four frequent intragenic polymorphisms did not reveal allelic association of the VMD2 locus with AMD. These data exclude a direct role of VMD2 in the predisposition to AMD.

Adolescent↗
PubMed2000

[Venous cross-sectional area: measured or calculated?].

AIM: The aim of this study was to compare measured versus calculated venous cross-sectional area in healthy subjects in a standing and a lying position with normal breath-ing and during Valsalva manoeuvre. METHOD: Measurements were carried out in 30 venous segments (the common femoral vein CFV, the superficial femoral vein SFV, the greater saphenous vein GSV) of 5 healthy volunteers (4 female, 1 male) with a median age of 28.7 years (range 23.4-46.7 years) in supine and standing position, while normally breathing and during a standardised Valsalva manoeuvre. Venous diameters were measured from B-mode in longitudinal view while cross-sectional areas were planimetrically assessed from transverse B-mode as recorded on video (S-VHS). The mathematical calculation of areas followed the formula (0.5 diameter)2 x pi. All investigations were performed 3 times; mean values from these 3 measurements were used for further computation. Measurements were performed using the NIH Image 1.6 program. RESULTS: Correlation coefficients r of the calculated versus the measured venous area while normal breathing in standing and in lying subjects were: 0.92 and 0.82 in the CFV, 0.92 and 0.84 in the SFV as well as 0.98 and 0.97 in the GSV, respectively. During Valsalva manoeuvre in standing and lying subjects the correlation coefficients r amounted to: 0.94 and 0.93 in the CFV, 0.92 and 0.94 in the SFV as well as 0.99 and 0.98 in the GSV, respectively. CONCLUSIONS: In healthy volunteers measured and calculated venous cross-sectional area at rest and during Valsalva manoeuvre correlate well. Correlation is numerically better in standing compared to lying subjects while normal breathing. Calculated venous area is accurate and can be used for further calculations.

Adult↗
PubMed2000

EST mining of the UniGene dataset to identify retina-specific genes.

Age-related macular degeneration (AMD) is a multifactorial disorder affecting the visual system with a high prevalence among the elderly population but with no effective therapy available at present. To better understand the pathogenesis of this disorder, the identification of the genetic factors and the determination of their contribution to AMD is needed. Towards this goal, we are pursuing a strategy that makes use of the EST data processed in the UniGene database and aims at the generation of a comprehensive catalogue of genes preferentially active in the human retina. Subsequently, these genes will be systematically assessed in AMD. We performed a retina EST sampling and obtained a total of 673 clusters containing only retina ESTs as well as 568 clusters with at least 30% of the ESTs in each cluster originating from retina cDNA libraries. Of these, 180 representative EST clusters with varying retina and non-retina EST contents were analyzed for their in vitro expression. This approach identified 39 transcripts with retina-specific expression. One of these genes (C18orf2) mapping to chromosome 18 was further characterized. Multiple C18orf2 transcripts display a complex pattern of differential splicing in the human retina. The various isoforms encode hypothetical polypeptides with no homologies to known proteins or protein motifs.

Alternative Splicing↗
PubMed1999

Mapping and genomic characterization of the gene encoding diacylglycerol kinase gamma (DAGK3): assessment of its role in dominant optic atrophy (OPA1).

The family of diacylglycerol kinases (DAGKs) is known to play an important role in signal transduction linked to phospholipid turnover. In the fruitfly Drosophila melanogaster, a human DAGK ortholog, DGK2, was shown to underlie the phenotype of the visual mutant retinal degeneration A (rdgA). Previously, the gene encoding a novel member of the human DAGK family, termed DAGK3, was cloned and demonstrated to be abundantly expressed in the human retina. Based on these findings we reasoned that DAGK3 might be an excellent candidate gene for a human eye disease. In the present study, we report the genomic organization of the human DAGK3 gene, which spans over 30 kb of genomic DNA interrupted by 23 introns. In addition, we have mapped the gene locus by fluorescence in situ hybridization to 3q27-28, overlapping the chromosomal region known to contain the gene underlying dominant optic atrophy (OPA1), the most common form of hereditary atrophy of the optic nerve. Mutational analysis of the entire coding region of DAGK3 in 19 unrelated German OPA1 patients has not revealed any disease-causing mutations, therefore excluding DAGK3 as a major cause underlying OPA1.

Adolescent↗
PubMed1999

The value of rapid D-dimer testing combined with structured clinical evaluation for the diagnosis of deep vein thrombosis.

PURPOSE: Large studies have shown that most cases referred for duplex sonography for suspected deep vein thrombosis (DVT) have normal scan results. For medical and economic reasons, a preselection procedure, which allows the detection of true-negative cases before duplex scanning, is required; this procedure should be characterized by a high sensitivity and a high negative predictive value. METHODS: In 343 patients (398 lower extremities) with suspected DVT, the DVT probability was clinically assessed, and a whole blood D-dimer agglutination test and a duplex scan were performed. The diagnostic sensitivities of the D-dimer test alone, a high clinical DVT probability alone, and the combination of both were evaluated. RESULTS: The sensitivity values for the D-dimer test to diagnose proximal and distal DVTs were 88.7% and 80.9%, the negative predictive values (NPV) were 96.3% and 97.9%, and the specificity and the positive predictive value (PPV) were 54.8% and 49.6% and 26.6% and 8.2%, respectively. The sensitivities of the clinical DVT probability assessment for the diagnosis of proximal and distal DVTs were 83.9% and 66.7%, respectively; the corresponding NPVs were 94.9% and 96.5%, respectively. The specificity was 56.1% and 50.8%, and the PPVs were 26.1% and 7.0%, respectively. The combined use of the results of the clinical probability assessment and the D-dimer test resulted in sensitivities for proximal and distal DVTs of 98.4% and 90.5%, NPVs of 99.3% and 98.6%, a specificity of 43.4% and 38.4%, and PPVs of 24. 3% and 7.6%, respectively. CONCLUSION: The combined use of a clinical DVT probability assessment scheme and the D-dimer test largely avoids false negative results, has a high sensitivity and NPV, helps to reduce the costs of DVT diagnosis, and may, in the future, be useful as a preselection procedure before duplex sonography.

Female↗
PubMed1999

Assessment of RS1 in X-linked juvenile retinoschisis and sporadic senile retinoschisis.

The RS1 gene is the causative gene in X-linked juvenile retinoschisis (RS). We have screened this gene for mutations in 13 patients with RS and in 7 probands with senile retinoschisis, a sporadic, later-onset form of retinoschisis. Mutations were detected in all RS patients. Of the 11 different mutations identified, six have been reported previously and live are novel. We did not find mutations in any of the senile retinoschisis patients and conclude that senile retinoschisis is not the result of germline mutations in the RS1 gene.

Adult↗
PubMed1998

Transcript map of a 900-kb genomic region in Xp22.1-p22.2: identification of 12 novel genes.

The Xp22.1-p22.2 interval is a focus of interest as a number of hereditary disease loci have been mapped to this region, including X-linked nonsyndromic sensorineural deafness (DFN6), X-linked juvenile retinoschisis (RS), and several X-linked mental retardation syndromes. In the course of cloning the RS gene we have assembled YAC and PAC contigs of the 900-kb candidate region delimited by DXS418 and DXS999. In this study, we now report the construction of a first transcript map of this chromosomal interval by combining exon trapping, EST mapping, and computational gene identification methods. Overall, this strategy has led to the assembly of at least 12 novel transcripts positioned within the DXS418-DXS999 region, one of these encoding a putative protein kinase motif with significant homology to the rat p58/GTA protein kinase domain and another a putative neuronal protein with strong homology to a Drosophila transcriptional repressor.

Amino Acid Sequence↗
PubMed1998

Assessment of the interphotoreceptor matrix proteoglycan-1 (IMPG1) gene localised to 6q13-q15 in autosomal dominant Stargardt-like disease (ADSTGD), progressive bifocal chorioretinal atrophy (PBCRA), and North Carolina macular dystrophy (MCDR1).

We have recently characterised the genomic organisation of a novel interphotoreceptor matrix proteoglycan, IMPG1, and have mapped the gene locus to chromosome 6q13-q15 by fluorescence in situ hybridisation. As the interphotoreceptor matrix (IPM) is thought to play a critical role in retinal adhesion and the maintenance of photoreceptor cells, it is conceivable that a defect in one of the IPM components may cause degenerative lesions in retinal structures and thus may be associated with human retinopathies. By genetic linkage analysis, several retinal dystrophies including one form of autosomal dominant Stargardt-like macular dystrophy (STGD3), progressive bifocal chorioretinal atrophy (PBCRA), and North Carolina macular dystrophy (MCDR1) have previously been localised to a region on proximal 6q that overlaps the IMPG1 locus. We have therefore assessed the entire coding region of IMPG1 by exon amplification and subsequent single stranded conformational analysis in patients from 6q linked multigeneration families diagnosed with PBCRA and MCDR1, as well as a single patient from an autosomal dominant STGD pedigree unlinked to either of the two known STGD2 and STGD3 loci on chromosomes 13q and 6q, respectively. No disease associated mutations were identified. In addition, using an intragenic polymorphism, IMPG1 was excluded by genetic recombination from both the PBCRA and the MCDR1 loci. However, as the autosomal dominant Stargardt-like macular dystrophies are genetically heterogeneous, other forms of this disorder, in particular STGD3 previously linked to 6q, may be caused by mutations in IMPG1.

Adult↗
PubMed1998

Genomic organization and chromosomal localization of the interphotoreceptor matrix proteoglycan-1 (IMPG1) gene: a candidate for 6q-linked retinopathies.

The interphotoreceptor matrix is a unique extracellular matrix occupying the space between the photoreceptors and the retinal pigment epithelium. Due to its putative function in the maintenance and integrity of the photoreceptor cells, it is conceivable that it is involved in retinal degeneration processes. More recently, a novel gene encoding a 150-kDa interphotoreceptor matrix proteoglycan, designated IMPG1, was cloned and shown to be expressed in both rod and cone photoreceptor cells. To assess this gene in human retinal dystrophies, we have now determined the genomic organization and chromosome location of IMPG1. It is composed of 17 exons ranging from 21 to 533 bp, including an alternatively spliced exon 2. Using somatic cell hybrid mapping and FISH analysis, we have assigned the IMPG1 locus to 6q13-->q15. As this interval overlaps with the chromosomal loci of several human retinopathies, including autosomal dominant Stargardt-like macular dystrophy (STGD3), progressive bifocal chorioretinal atrophy (PBCRA), and North Carolina macular dystrophy (MCDR1), IMPG1 represents an attractive candidate for these 6q-linked disorders.

Alternative Splicing↗
PubMed1997

Cloning of the homogentisate 1,2-dioxygenase gene, the key enzyme of alkaptonuria in mouse.

We determined 48 amino acid residues from five peptides from the homogeneous monomer of homogentisate 1,2-dioxygenase (HGO; E.C. 1.13. 11.15) of mouse liver. After digestion with trypsin, peptides were separated by reversed phase chromatography and amino acid sequenced. The deduced codon sequence of three peptides was used to derive degenerated oligomeres. By combining these oligos, we were able to amplify fragments from 100 to 300 bases (b) from mouse liver cDNA by polymerase chain reaction after reverse transcription (RT-PCR). A fragment of 200 b was cloned and used as a probe to screen a mouse liver cDNA library. One clone from this library contained the complete cDNA-insert for HGO as determined by sequencing. The cDNA encodes for a protein of 50 kDa, as predicted. The cDNA of mouse HGO has an overall identity of 41% to the corresponding gene hmgA from Aspergillus. Sequence similarities to human expressed sequence tags (EST) clones ranged from 70% to 20%. The positions of 122 conserved amino acids could be determined by multiple sequence alignment. We identified one first intron of 928 b in the mouse gene. The gene for HGO seems to be expressed in various tissues, as shown by RT-PCR on different cDNAs. FISH experiments with the whole murine cDNA as probe clearly revealed signals at the human chromosomal band 3q13. 3-q21. This corresponds well to the previous assignment of the locus for the human alkaptonuria gene (AKU) to the same chromosomal region by multipoint linkage analysis. We therefore conclude that the HGO cDNA encodes the gene responsible for alkaptonuria.

Alkaptonuria↗
PubMed1997

Positional cloning of the gene associated with X-linked juvenile retinoschisis.

X-linked juvenile retinoschisis(RS) is a recessively inherited vitreo-retinal degeneration characterized by macular pathology and intraretinal splitting of the retina. The RS gene has been localized to Xp22.2 to an approximately 1 Mb interval between DXS418 and DXS999/DXS7161. Mapping and expression analysis of expressed sequence tags have identified a novel transcript, designated XLRS1, within the centromeric RS locus that is exclusively expressed in retina. The predicted XLRS1 protein contains a highly conserved motif implicated in cell-cell interaction and thus may be active in cell adhesion processes during retinal development. Mutational analyses of XLRS1 in affected individuals from nine unrelated RS families revealed one nonsense, one frameshift, one splice acceptor and six missense mutations segregating with the disease phenotype in the respective families. These data provide strong evidence that the XLRS1 gene, when mutated, causes RS.

Amino Acid Sequence↗
PubMed1997

Molecular defects in alkaptonuria.

At the dawn of human genetics Sir Archibald Garrod used alkaptonuria as a paradigm to demonstrate the applicability of the Mendelian laws to men and to develop the concept of inborn errors of metabolism. The human cDNA for homogentisate 1,2 dioxygenase was identified due to its homology to the corresponding mouse enzyme and was screened for mutations in alkaptonuric patients from Slovakia. Homozygous mutations were found in four unrelated families and their segregation with the disease was demonstrated. One of the mutations, observed in two families, leads to a frame-shift and thus is unlikely to produce functional protein. The data formally establish the homogentisate 1,2 dioxygenase gene (HGD) as the molecular cause of alkaptonuria and allow for the development of molecular carrier tests in populations at risk.

Alkaptonuria↗
PubMedDate not supplied

Chondrogenesis of limb-bud cells: improved culture method and the effect of the potent teratogen retinoic acid.

A new apparatus for the mild and reproducible dissociation of rat limb buds into single cells is described. The growth and differentiation of the embryonic mesenchyme cells into chrondrocytes was markedly affected by the conditions of tissue dissociation and the serum used. The degree of chondrogenesis was assessed by alcian blue staining, specific for cartilage matrix. Retinoic acid, a known teratogen, inhibited chondrogenesis completely in a dose-dependent manner. The determination of the quantifiable end-point, IC50 in this cell-culture system, may be suitable to compare the activity of various retinoids and eventually to determine their teratogenic potential.

Animals↗