Biomedical subjects

W Edelmann

Publications and source records attributed to W Edelmann.

At least 19 recordsLinked to original sources

PubMed2005

Functional consequences of DNA mismatch repair missense mutations in murine models and their impact on cancer predisposition.

Mutations in MMR (DNA mismatch repair) genes underlie HNPCC (hereditary non-polyposis colon cancer) and also a significant proportion of sporadic colorectal cancers. MMR maintains genome stability and suppresses tumour formation by correcting DNA replication errors and by mediating an apoptotic response to DNA damage. Analysis of mouse lines with MMR missense mutations demonstrates that these MMR functions can be separated and allows the assessment of their individual roles in tumour suppression. These studies in mice indicate that, although the increased mutation rates caused by MMR defects are sufficient to drive tumorigenesis, both functions co-operate in tumour suppression.

Animals↗

PubMed2005

Environmental aspects of the anaerobic digestion of the organic fraction of municipal solid wastes and of solid agricultural wastes.

In order to obtain more detailed information for better decision making in future biogenic waste treatment, different processes to treat biogenic wastes in plants with a treatment capacity of 10,000 tons of organic household wastes per year as well as agricultural codigestion plants were compared by life cycle assessments (LCA). With the tool EcoIndicator, anaerobic digestion is shown to be advantageous as compared to composting, incineration or a combination of digestion and composting, mainly because of a better energy balance. The management of the liquid manure in agricultural codigestion of organic solid wastes causes increased gaseous emissions, which have negative effects on the LCA, however. It is recommended to cover the slurry pit and to use an improved manure management in order to compensate for the additional gaseous emissions. In the LCAs, the quality of the digester output could only be taken into account to a small extent; the reasons are discussed.

Agriculture↗

PubMed2001

A new mouse model for evaluating the immunotherapy of human colorectal cancer.

A new murine model of human colorectal cancer was generated by crossing human carcinoembryonic antigen (CEA) transgenic mice (H-2K(b)) with adenomatous polyposis coli (Apc1638N) knockout mice (H-2K(b)). The resulting hybrid mice developed gastrointestinal polyps in 6-8 months that progressed to invasive carcinomas with a similar pattern of dysplasia and CEA expression as observed in human colorectal cancer. These animals exhibited incomplete or partial tolerance to CEA as evidenced by delayed growth of CEA-expressing tumors and the inability to inhibit CEA-specific CTL responses. These results have important implications for understanding the role of CEA-specific immunity in human colon cancer patients and suggest that vaccine strategies targeting CEA may be feasible. This model provides a powerful system for evaluating antigen-specific tumor immunity against spontaneous tumors arising in an orthotopic location and permits evaluation of therapeutic vaccine strategies for human colorectal cancer.

Adenocarcinoma↗

PubMed2001

The distinct spectra of tumor-associated Apc mutations in mismatch repair-deficient Apc1638N mice define the roles of MSH3 and MSH6 in DNA repair and intestinal tumorigenesis.

In mammalian cells, mismatch recognition has been attributed to two partially redundant heterodimeric protein complexes of MutS homologues, MSH2-MSH3 and MSH2-MSH6. We have conducted a comparative analysis of Msh3 and Msh6 deficiency in mouse intestinal tumorigenesis by generating Apc1638N mice deficient in Msh3, Msh6 or both. We have found that Apc1638N mice defective in Msh6 show reduced survival and a 6-7-fold increase in intestinal tumor multiplicity. In contrast, Msh3-deficient Apc1638N mice showed no difference in survival and intestinal tumor multiplicity as compared with Apc1638N mice. However, when Msh3 deficiency is combined with Msh6 deficiency (Msh3(-/-)Msh6(-/-)Apc1638N), the survival rate of the mice was further reduced compared to Msh6(-/-)Apc(1638N) mice because of a high multiplicity of intestinal tumors at a younger age. Almost 90% of the intestinal tumors from both Msh6(-/-)Apc1638N and Msh3(-/-)Msh6(-/-)Apc1638N mice contained truncation mutations in the wild-type Apc allele. Apc mutations in Msh6(-/-)Apc1638N mice consisted predominantly of base substitutions (93%) creating stop codons, consistent with a major role for Msh6 in the repair of base-base mismatches. However, in Msh3(-/-)Msh6(-/-)Apc1638N tumors, we observed a mixture of base substitutions (46%) and frameshifts (54%), indicating that in Msh6(-/-)Apc1638N mice frameshift mutations in the Apc gene were suppressed by Msh3. Interestingly, all except one of the Apc mutations detected in mismatch repair-deficient intestinal tumors were located upstream of the third 20-amino acid beta-catenin binding repeat and before all of the Ser-Ala-Met-Pro repeats, suggesting that there is selection for loss of multiple domains involved in beta-catenin regulation. Our analysis therefore has revealed distinct mutational spectra and clarified the roles of Msh3 and Msh6 in DNA repair and intestinal tumorigenesis.

Animals↗

PubMed2001

p21(WAF1/cip1) is an important determinant of intestinal cell response to sulindac in vitro and in vivo.

Sulindac, a nonsteroidal anti-inflammatory drug, inhibits intestinal tumorigenesis in humans and rodents. Sulindac induced complex alterations in gene expression, but only 0.1% of 8063 sequences assayed were altered similarly by the drug in rectal biopsies of patients treated for 1 month and during response of colonic cells in culture. Among these changes was induction of the cyclin-dependent kinase inhibitor, p21(WAF1/cip1). In Apc1638(+/-) mice, targeted inactivation of p21 increased intestinal tumor formation in a gene-dose-dependent manner, but inactivation of p21 completely eliminated the ability of sulindac to both inhibit mitotic activity in the duodenal mucosa and to inhibit Apc-initiated tumor formation. Thus, p21 is essential for tumor inhibition by this drug. The array data can be accessed on the Internet at http://sequence.aecom.yu.edu/genome/.

Animals↗

PubMed2001

Caveolin-1 null mice are viable but show evidence of hyperproliferative and vascular abnormalities.

Caveolin-1 is the principal structural protein of caveolae membranes in fibroblasts and endothelia. Recently, we have shown that the human CAV-1 gene is localized to a suspected tumor suppressor locus, and mutations in Cav-1 have been implicated in human cancer. Here, we created a caveolin-1 null (CAV-1 -/-) mouse model, using standard homologous recombination techniques, to assess the role of caveolin-1 in caveolae biogenesis, endocytosis, cell proliferation, and endothelial nitric-oxide synthase (eNOS) signaling. Surprisingly, Cav-1 null mice are viable. We show that these mice lack caveolin-1 protein expression and plasmalemmal caveolae. In addition, analysis of cultured fibroblasts from Cav-1 null embryos reveals the following: (i) a loss of caveolin-2 protein expression; (ii) defects in the endocytosis of a known caveolar ligand, i.e. fluorescein isothiocyanate-albumin; and (iii) a hyperproliferative phenotype. Importantly, these phenotypic changes are reversed by recombinant expression of the caveolin-1 cDNA. Furthermore, examination of the lung parenchyma (an endothelial-rich tissue) shows hypercellularity with thickened alveolar septa and an increase in the number of vascular endothelial growth factor receptor (Flk-1)-positive endothelial cells. As predicted, endothelial cells from Cav-1 null mice lack caveolae membranes. Finally, we examined eNOS signaling by measuring the physiological response of aortic rings to various stimuli. Our results indicate that eNOS activity is up-regulated in Cav-1 null animals, and this activity can be blunted by using a specific NOS inhibitor, nitro-l-arginine methyl ester. These findings are in accordance with previous in vitro studies showing that caveolin-1 is an endogenous inhibitor of eNOS. Thus, caveolin-1 expression is required to stabilize the caveolin-2 protein product, to mediate the caveolar endocytosis of specific ligands, to negatively regulate the proliferation of certain cell types, and to provide tonic inhibition of eNOS activity in endothelial cells.

Albumins↗

PubMed2001

Rescue of embryonic lethality in reduced folate carrier-deficient mice by maternal folic acid supplementation reveals early neonatal failure of hematopoietic organs.

The reduced folate carrier (RFC1) is an important route by which the major blood folate, 5-methyltetrahydrofolate, is transported into mammalian cells. In this study we determined the consequences of inactivation of RFC1 in mice by homologous recombination. While RFC1-null embryos died in utero before embryonic day 9.5 (E9.5), near-normal development could be sustained in RFC1(-)/- embryos examined at E18.5 by supplementation of pregnant RFC1(+/-) dams with 1-mg daily subcutaneous doses of folic acid. About 10% of these animals went on to live birth but died within 12 days. These RFC1(-)/- mice showed a marked absence of erythropoiesis in bone marrow, spleen, and liver along with lymphoid depletion in the splenic white pulp and thymus. In addition, there was some impairment of renal and seminiferous tubule development. These data indicate that in the absence of RFC1 function, neonatal animals die due to failure of hematopoietic organs.

Alleles↗

PubMed2001

Caveolin-3 null mice show a loss of caveolae, changes in the microdomain distribution of the dystrophin-glycoprotein complex, and t-tubule abnormalities.

Caveolin-3, a muscle-specific caveolin-related protein, is the principal structural protein of caveolae membrane domains in striated muscle cells. Recently, we identified a novel autosomal dominant form of limb-girdle muscular dystrophy (LGMD-1C) in humans that is due to mutations within the coding sequence of the human caveolin-3 gene (3p25). These LGMD-1C mutations lead to an approximately 95% reduction in caveolin-3 protein expression, i.e. a caveolin-3 deficiency. Here, we created a caveolin-3 null (CAV3 -/-) mouse model, using standard homologous recombination techniques, to mimic a caveolin-3 deficiency. We show that these mice lack caveolin-3 protein expression and sarcolemmal caveolae membranes. In addition, analysis of skeletal muscle tissue from these caveolin-3 null mice reveals: (i) mild myopathic changes; (ii) an exclusion of the dystrophin-glycoprotein complex from lipid raft domains; and (iii) abnormalities in the organization of the T-tubule system, with dilated and longitudinally oriented T-tubules. These results have clear mechanistic implications for understanding the pathogenesis of LGMD-1C at a molecular level.

Animals↗

PubMed2001

Targeted inactivation of the p21(WAF1/cip1) gene enhances Apc-initiated tumor formation and the tumor-promoting activity of a Western-style high-risk diet by altering cell maturation in the intestinal mucosal.

Elimination of both alleles of the gene that encodes the cyclin kinase inhibitor p21(WAF1/cip1) increases the frequency and size of intestinal tumors in Apc1638+/- mice that inherit a mutant allele of the Apc gene, and intermediate effects are seen if a single p21 allele is inactivated. The increased tumor formation is associated with altered cell maturation in the intestinal mucosa of the p21-deficient mice--increased cell proliferation, and decreased apoptosis, and goblet cell differentiation--that is also a function of p21 gene dosage. Moreover, a Western-style diet that mimics principal risk factors for colon cancer (high fat and phosphate, low calcium and vitamin D) accelerates tumor formation in Apc1638+/- mice, and the loss of a single or both p21 alleles is additive with the tumor-promoting effects of this diet, resulting in more and larger tumors, and a highly significant decrease in survival time. Thus, p21 normally suppresses Apc-initiated tumor formation and is haplo-insufficient in this regard. This is consistent with recent reports that Apc initiates tumor formation by up-regulating c-myc expression through altered beta-catenin-Tcf signaling and that c-myc then up-regulates cdk4, whose activity is inhibited by p21. Decreased expression of p21 is also a marker of poor prognosis in patients, and the data presented suggest that dietary alterations in patients undergoing treatment for colon cancer might be highly effective in improving outcome.

Adenomatous Polyposis Coli Protein↗

PubMed2001

Mouse models for human familial adenomatous polyposis.

Colorectal cancer (CRC) is the second most frequent type of cancer in the Western hemisphere. In the United States alone, it is estimated that 150 000 new cases are detected every year and more than 65 000 patients die from complications associated with this cancer. Identification of genes implicated in the initiation and progression of colorectal cancer in humans has prompted the generation of mouse models for this cancer. We will provide a brief overview of these mouse models for CRC and what they have contributed to our understanding of the events involved in the initiation and progression of this cancer.

Adenomatous Polyposis Coli↗

PubMed2000

Tumor-associated Apc mutations in Mlh1-/- Apc1638N mice reveal a mutational signature of Mlh1 deficiency.

Apc1638N mice, which are heterozygous for a germline mutation in Apc, typically develop three to five spontaneous intestinal tumors per animal. In most cases this is associated with allelic loss of wildtype Apc. We have previously reported that the multiplicity of intestinal tumors is increased dramatically by crossing Apc1638N with an Mlh1-deficient mouse strain that represents an animal model of hereditary non-polyposis colorectal cancer (HNPCC). The increased tumor multiplicity in these mice was associated with somatic mutations in the Apc tumor suppressor gene. Here, we have examined the nature and distribution of 91 Apc mutations implicated in the development of intestinal tumors in Mlh1-/- Apc1638N animals. Protein truncation mutations were detected in a majority of tumor samples, indicating that the prevailing mechanism of Apc mutation in tumors is altered from allelic loss to intragenic mutation as a result of Mlh1 deficiency. The observed mutations were a mixture of base substitutions (27%) and frameshifts (73%). Most frameshifts were detected within dinucleotide repeats and there were prominent mutational hotspots within sequences of this sort at codons 927-929, 1209-1211 and 1461-1464. The observed Apc mutations caused protein truncation upstream of the third 20 amino acid beta-catenin binding domain and the first Axin-binding SAMP repeat, yielding Apc proteins that are predicted to be deficient in destabilizing beta-catenin. Our results reveal a characteristic mutational signature in Apc that is attributable to Mlh1 deficiency. This demonstrates a direct effect of Mlh1 deficiency in the mutation of Apc in these tumors, and provides data that clarify the role of Mlh1 in mammalian DNA mismatch repair.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Ultrastructural and ERG findings in mice with adenomatous polyposis coli gene disruption.

PURPOSE: In order to continue the previous morphological studies of eyes from mice with adenomatous polyposis coli (APC) gene mutation at codon 1638, we determined the ultrastructural and electrophysiologic characteristics of these eyes. METHODS: Thirty-eight eyes from 20 mice heterozygous for APC gene mutation and 22 eyes from 11 wild-type mice were examined by light microscopy. Six APC-modified eyes without light microscopic abnormalities, four APC-modified eyes with focal light microscopic abnormalities, and four wild-type eyes were examined by electron microscopy. Electroretinograms were recorded from four APC-modified and three wild-type mice. RESULTS: Four of 38 APC-modified eyes demonstrated ultrastructural evidence of focal RPE cells with increased melanosome production and atrophy. Other areas of the RPE in these four eyes demonstrated no ultrastructural abnormalities. Three APC-modified eyes demonstrated electron and light microscopic evidence of RPE hyperplasia. Electron microscopic examination of APC-modified eyes without light microscopic evidence of abnormalities demonstrated no ultrastructural differences from age-matched controls. Electroretinography demonstrated no differences in the b-wave or c-wave amplitudes between APC-modified and wild-type mice. CONCLUSIONS: While light microscopic RPE alterations are observed in these APC-modified mice, the absence of a generalized, ultrastructural murine RPE defect is in contradistinction to observations in electron microscopic investigations of humans with colonic polyposis, pigmented ocular fundus lesions, and APC gene mutations between codons 463 and 1444. Our results in mice with APC mutation at codon 1638, however, are consistent with a previously identified association between the expression of pigmented ocular fundus lesions and region-specific mutation in the human APC gene. The APC protein may possess a physiologic function for both retinal and RPE development.

Adenomatous Polyposis Coli↗

PubMed2000

MutS homolog 4 localization to meiotic chromosomes is required for chromosome pairing during meiosis in male and female mice.

Msh4 (MutS homolog 4) is a member of the mammalian mismatch repair gene family whose members are involved in postreplicative DNA mismatch repair as well as in the control of meiotic recombination. In this report we show that MSH4 has an essential role in the control of male and female meiosis. We demonstrate that MSH4 is present in the nuclei of spermatocytes early in prophase I and that it forms discrete foci along meiotic chromosomes during the zygotene and pachytene stages of meiosis. Disruption of the Msh4 gene in mice results in male and female sterility due to meiotic failure. Although meiosis is initiated in Msh4 mutant male and female mice, as indicated by the chromosomal localization of RAD51 and COR1 during leptonema/zygonema, the chromosomes fail to undergo normal pairing. Our results show that MSH4 localization on chromosomes during the early stages of meiosis is essential for normal chromosome synapsis in prophase I and that it acts in the same pathway as MSH5.

Animals↗

PubMed2000

The DNA mismatch repair genes Msh3 and Msh6 cooperate in intestinal tumor suppression.

Repair of mismatches in DNA in mammalian cells is mediated by a complex of proteins that are members of two highly conserved families of genes referred to as MutS and MutL homologues. Germline mutations in several members of these families, MSH2, MSH6, MLH1, and PMS2, but not MSH3, are responsible for hereditary non-polyposis colorectal cancer. To examine the role of MSH3, we generated a mouse with a null mutation in this gene. Cells from Msh3-/- mice are defective in repair of insertion/ deletion mismatches but can repair base-base mismatches. Msh3-/- mice develop tumors at a late age. When the Msh3-/- and Msh6-/- mutations are combined, the tumor predisposition phenotype is indistinguishable from Msh2-/- or Mlh1-/- mice. These results suggest that MSH3 cooperates with MSH6 in tumor suppression.

Animals↗

PubMed2000

Somatic hypermutation in MutS homologue (MSH)3-, MSH6-, and MSH3/MSH6-deficient mice reveals a role for the MSH2-MSH6 heterodimer in modulating the base substitution pattern.

Although the primary function of the DNA mismatch repair (MMR) system is to identify and correct base mismatches that have been erroneously introduced during DNA replication, recent studies have further implicated several MMR components in somatic hypermutation of immunoglobulin (Ig) genes. We studied the immune response in mice deficient in MutS homologue (MSH)3 and MSH6, two mutually exclusive partners of MSH2 that have not been examined previously for their role in Ig hypermutation. In Msh6(-)/- and Msh3(-)/-/Msh6(-)/- mice, base substitutions are preferentially targeted to G and C nucleotides and to an RGYW hot spot, as has been shown previously in Msh2(-)/- mice. In contrast, Msh3(-)/- mice show no differences from their littermate controls. These findings indicate that the MSH2-MSH6 heterodimer, but not the MSH2-MSH3 complex, is responsible for modulating Ig hypermutation.

Adenosine Triphosphatases↗

PubMed2000

Somatic Apc mutations are selected upon their capacity to inactivate the beta-catenin downregulating activity.

The APC gene, originally identified as the gene for familial adenomatous polyposis (FAP), is now considered as the true "gatekeeper" of colonic epithelial proliferation. Its main tumor suppressing activity seems to reside in the capacity to properly regulate intracellular beta-catenin signaling. Most somatic APC mutations are detected between codons 1286 and 1513, the mutation cluster region (MCR). This clustering can be explained either by the presence of mutation-prone sequences within the MCR, or by the selective advantage provided by the resulting truncated polypeptides. Here, a Msh2-deficient mouse model (Msh2(delta 7N) ) was generated and bred with Apc(1638N) and Apc(Min) that allowed the comparison of the somatic mutation spectra along the Apc gene in the different allelic combinations. Mutations identified in Msh2(delta 7N/delta 7N) tumors are predominantly dinucleotide deletions at simple sequence repeats leading to truncated Apc polypeptides that partially retain the 20 a.a. beta-catenin downregulating motifs. In contrast, the somatic mutations identified in the wild type Apc allele of Msh2(delta 7N/delta 7N) /Apc(+/1638N) and Msh2(delta 7N/delta 7N) /Apc(+/Min) tumors are clustered more to the 5' end, thereby completely inactivating the beta-catenin downregulating activity of APC. These results indicate that somatic Apc mutations are selected during intestinal tumorigenesis and that inactivation of the beta-catenin downregulating function of APC is likely to represent the main selective factor.

Adenomatous Polyposis Coli↗

PubMed2000

Cardiac defects and renal failure in mice with targeted mutations in Pkd2.

PKD2, mutations in which cause autosomal dominant polycystic kidney disease (ADPKD), encodes an integral membrane glycoprotein with similarity to calcium channel subunits. We induced two mutations in the mouse homologue Pkd2 (ref.4): an unstable allele (WS25; hereafter denoted Pkd2WS25) that can undergo homologous-recombination-based somatic rearrangement to form a null allele; and a true null mutation (WS183; hereafter denoted Pkd2-). We examined these mutations to understand the function of polycystin-2, the protein product of Pkd2, and to provide evidence that kidney and liver cyst formation associated with Pkd2 deficiency occurs by a two-hit mechanism. Pkd2-/- mice die in utero between embryonic day (E) 13.5 and parturition. They have structural defects in cardiac septation and cyst formation in maturing nephrons and pancreatic ducts. Pancreatic ductal cysts also occur in adult Pkd2WS25/- mice, suggesting that this clinical manifestation of ADPKD also occurs by a two-hit mechanism. As in human ADPKD, formation of kidney cysts in adult Pkd2WS25/- mice is associated with renal failure and early death (median survival, 65 weeks versus 94 weeks for controls). Adult Pkd2+/- mice have intermediate survival in the absence of cystic disease or renal failure, providing the first indication of a deleterious effect of haploinsufficiency at Pkd2on long-term survival. Our studies advance our understanding of the function of polycystin-2 in development and our mouse models recapitulate the complex human ADPKD phenotype.

Animals↗

PubMed2000

Co-digestion of organic solid waste and sludge from sewage treatment.

Solid organic wastes were codigested together with sludge of a sewage treatment plant (STP). In the practical part of the study, a plant to pretreat the organic solid wastes provided by local super markets was constructed at the STP of Frutigen, Switzerland. Up to more than 1 cubic metre of wastes was added to the fermenter of the STP every day. Data collected during 14 months of practical works, showed that for raw fruit and vegetable wastes a two step pretreatment is necessary: First the wastes were chopped and afterwards reduced to a size of 1-2 millimetres, in order to get a homogeneous suspension together with the primary sludge. The vegetable wastes showed excellent digestibility: They seemed to accelerate the digestion process as well as to increase the degree of the anaerobic degradation of the sludge. The energy demand for both, pretreatment and digestion, was 85 kWh/ton of fresh wastes. 20% of the energy was used for the hygienization, a step which does not seem to be necessary for this kind of waste in most of the cases, however. After using the gas for energy conversion, a net yield of 65 kWh/ton of electricity and 166 kWh/ton of heat was measured. Treating cooked kitchen wastes, the net energy production will be higher, because in this case a one step pretreatment will be sufficient. The pretreatment and treatment costs for codigestion on STP's were calculated to be in the range of 55 US$/ton treating half a ton per day and 39 US$/ton treating one ton, respectively. A theoretical feasibility study showed that in Switzerland there is a short term potential on STP's for the codigestion of about 120,000 tons of biogenic wastes per year without big investments. Economic studies about codigestion on agricultural biogas plants showed that the codigestion is a must at the current energy prices, which are far too low for agricultural AD without an additional income by treating solid wastes for third parties.

Bacteria, Anaerobic↗