Biomedical subjects

Theo G M F Gorgels

Publications and source records attributed to Theo G M F Gorgels.

7 recordsLinked to original sources

PubMed2006

Retinal degeneration and ionizing radiation hypersensitivity in a mouse model for Cockayne syndrome.

Mutations in the CSB gene cause Cockayne syndrome (CS), a DNA repair disorder characterized by UV sensitivity and severe physical and neurological impairment. CSB functions in the transcription-coupled repair subpathway of nucleotide excision repair. This function may explain the UV sensitivity but hardly clarifies the other CS symptoms. Many of these, including retinopathy, are associated with premature aging. We studied eye pathology in a mouse model for CS. Csb(m/m) mice were hypersensitive to UV light and developed epithelial hyperplasia and squamous cell carcinomas in the cornea, which underscores the importance of transcription-coupled repair of photolesions in the mouse. In addition, we observed a spontaneous loss of retinal photoreceptor cells with age in the Csb(m/m) retina, resulting in a 60% decrease in the number of rods by the age of 18 months. Importantly, when Csb(m/m) mice (as well as Csa(-/-) mice) were exposed to 10 Gy of ionizing radiation, we noticed an increase in apoptotic photoreceptor cells, which was not observed in wild-type animals. This finding, together with our observation that the expression of established oxidative stress marker genes is upregulated in the Csb(m/m) retina, suggests that (endogenous) oxidative DNA lesions play a role in this CS-specific premature-aging feature and supports the oxidative DNA damage theory of aging.

Animals↗

PubMed2006

ABCC6 and pseudoxanthoma elasticum.

ABCC6 belongs to the adenosine triphosphate-binding cassette (ABC) gene subfamily C. This protein family is involved in a large variety of physiological processes, such as signal transduction, protein secretion, drug and antibiotic resistance, and antigen presentation [Kool et al. (1999) 59:175-182; Borst and Elferink (2002) 71:537-592]. ABCC6 is primarily and highly expressed in the liver and kidney [Kool et al. (1999) 59:175-182; Bergen et al. (2000) 25:228-2231]. The precise physiological function and natural substrate(s) transported by ABCC6 are unknown, but the protein may be involved in active transport of intracellular compounds to the extracellular environment [Kool et al. (1999) 59:175-182] [Scheffer et al. (2002) 82:515-518]. Recently, it was shown that loss of function mutations in ABCC6 cause pseudoxanthoma elasticum (PXE) [Bergen et al. (2000) 25:228-2231; Le Saux et al. (2000) 25:223-227]. PXE is an autosomal recessively inherited multi-organ disorder [Goodman et al. (1963) 42:297-334; Lebwohl et al. (1994) 30:103-107]. PXE is primarily associated with the accumulation of mineralized and fragmented elastic fibers of the connective tissue in the skin [Neldner (1988) 6:1-159], Bruch's membrane in the retina [Hu et al. (2003) 48:424-438], and vessel walls [Kornet et al. (2004) 30:1041-1048]. PXE patients usually have skin lesions and breaks in Bruch's membrane of the retina (angioid streaks). Also, a variety of cardiovascular complications has been observed [Hu et al. (2003) 48:424-438]. Recently, a mouse model for PXE was created by targeted disruption of Abcc6 [Gorgels et al. (2005) 14:1763-1773; Klement et al. (2005) 25:8299-8310], which may be useful to elucidate the precise function of Abcc6 and to develop experimental therapies.

ATP-Binding Cassette Transporters↗

PubMed2005

Disruption of Abcc6 in the mouse: novel insight in the pathogenesis of pseudoxanthoma elasticum.

Pseudoxanthoma elasticum (PXE) is a heritable disorder of connective tissue, affecting mainly skin, eye and the cardiovascular system. PXE is characterized by dystrophic mineralization of elastic fibres. The condition is caused by loss of function mutations in ABCC6. We generated Abcc6 deficient mice (Abcc6-/-) by conventional gene targeting. As shown by light and electron microscopy Abcc6-/- mice spontaneously developed calcification of elastic fibres in blood vessel walls and in Bruch's membrane in the eye. No clear abnormalities were seen in the dermal extracellular matrix. Calcification of blood vessels was most prominent in small arteries in the cortex of the kidney, but in old mice, it occurred also in other organs and in the aorta and vena cava. Newly developed monoclonal antibodies against mouse Abcc6 localized the protein to the basolateral membranes of hepatocytes and the basal membrane in renal proximal tubules, but failed to show the protein at the pathogenic sites. Abcc6-/- mice developed a 25% reduction in plasma HDL cholesterol and an increase in plasma creatinine levels, which may be due to impaired kidney function. No changes in serum mineral balance were found. We conclude that the phenotype of the Abcc6-/- mouse shares calcification of elastic fibres with human PXE pathology, which makes this model a useful tool to further investigate the aetiology of PXE. Our data support the hypothesis that PXE is in fact a systemic disease.

ATP-Binding Cassette Transporters↗

PubMed2003

Cell type-specific hypersensitivity to oxidative damage in CSB and XPA mice.

Mutations in the CSB gene cause Cockayne syndrome (CS), a rare inherited disorder, characterized by UV-sensitivity, severe neurodevelopmental and progeroid symptoms. CSB functions in the transcription-coupled repair (TCR) sub-pathway of nucleotide excision repair (NER), responsible for the removal of UV-induced and other helix-distorting lesions from the transcribed strand of active genes. Several lines of evidence support the notion that the CSB TCR defect extends to other non-NER type transcription-blocking lesions, notably various kinds of oxidative damage, which may provide an explanation for part of the severe CS phenotype. We used genetically defined mouse models to examine the relationship between the CSB defect and sensitivity to oxidative damage in different cell types and at the level of the intact organism. The main conclusions are: (1) CSB(-/-) mouse embryo fibroblasts (MEFs) exhibit a clear hypersensitivity to ionizing radiation, extending the findings in genetically heterogeneous human CSB fibroblasts to another species. (2) CSB(-/-) MEFs are highly sensitive to paraquat, strongly indicating that the increased cytotoxicity is due to oxidative damage. (3) The hypersenstivity is independent of genetic background and directly related to the CSB defect and is not observed in totally NER-deficient XPA MEFs. (4) Wild type embryonic stem (ES) cells display an increased sensitivity to ionizing radiation compared to fibroblasts. Surprisingly, the CSB deficiency has only a very minor additional effect on ES cell sensitivity to oxidative damage and is comparable to that of an XPA defect, indicating cell type-specific differences in the contribution of TCR and NER to cellular survival. (5) Similar to ES cells, CSB and XPA mice both display a minor sensitivity to whole-body X-ray exposure. This suggests that the response of an intact organism to radiation is largely determined by the sensitivity of stem cells, rather than differentiated cells. These findings establish the role of transcription-coupled repair in resistance to oxidative damage and reveal a cell- and organ-specific impact of this repair pathway to the clinical phenotype of CS and XP.

Animals↗

PubMed2002

Mitochondrial repair of 8-oxoguanine is deficient in Cockayne syndrome group B.

Reactive oxygen species, which are prevalent in mitochondria, cause oxidative DNA damage including the mutagenic DNA lesion 7,8-dihydroxyguanine (8-oxoG). Oxidative damage to mitochondrial DNA has been implicated as a causative factor in a wide variety of degenerative diseases, and in cancer and aging. 8-oxoG is repaired efficiently in mammalian mitochondrial DNA by enzymes in the base excision repair pathway, including the 8-oxoguanine glycosylase (OGG1), which incizes the lesion in the first step of repair. Cockayne syndrome (CS) is a segmental premature aging syndrome in humans that has two complementation groups, CSA and CSB. Previous studies showed that CSB-deficient cells have reduced capacity to repair 8-oxoG. This study examines the role of the CSB gene in regulating repair of 8-oxoG in mitochondrial DNA in human and mouse cells. 8-oxoG repair was measured in liver cells from CSB deficient mice and in human CS-B cells carrying expression vectors for wild type or mutant forms of the human CSB gene. For the first time we report that CSB stimulates repair of 8-oxoG in mammalian mitochondrial DNA. Furthermore, evidence is presented to support the hypothesis that wild type CSB regulates expression of OGG1.

Amino Acid Sequence↗

PubMed2002

UVB radiation-induced cancer predisposition in Cockayne syndrome group A (Csa) mutant mice.

Cockayne syndrome (CS) is an inherited photosensitive neurodevelopmental disorder caused by a specific defect in the transcription-coupled repair (TCR) sub-pathway of NER. Remarkably, despite their DNA repair deficiency, CS patients do not develop skin cancer. Here, we present a mouse model for CS complementation group A. Like cells from CS-A patients, Csa-/- mouse embryonic fibroblasts (MEFs): (i) are ultraviolet (UV)-sensitive; (ii) show normal unscheduled DNA synthesis (indicating that the global genome repair sub-pathway is unaffected); (iii) fail to resume RNA synthesis after UV-exposure and (iv) are unable to remove cyclobutane pyrimidine dimers (CPD) photolesions from the transcribed strand of active genes. CS-A mice exhibit UV-sensitivity and pronounced age-dependent loss of retinal photoreceptor cells but otherwise fail to show the severe developmental and neurological abnormalities of the human syndrome. In contrast to human CS, Csa-/- animals develop skin tumors after chronic exposure to UV light, indicating that TCR in mice protects from UV-induced skin cancer development. Strikingly, inactivation of one Xpc allele (encoding a component of the damage recognition complex involved in the global genome repair sub-pathway) in Csa-/- mice resulted in a strongly enhanced UV-mediated skin cancer sensitivity, indicating that in a TC repair defective background, the Xpc gene product may be a rate-limiting factor in the removal of UV-induced DNA lesions.

Amino Acid Sequence↗

PubMed2002

Developmental defects and male sterility in mice lacking the ubiquitin-like DNA repair gene mHR23B.

mHR23B encodes one of the two mammalian homologs of Saccharomyces cerevisiae RAD23, a ubiquitin-like fusion protein involved in nucleotide excision repair (NER). Part of mHR23B is complexed with the XPC protein, and this heterodimer functions as the main damage detector and initiator of global genome NER. While XPC defects exist in humans and mice, mutations for mHR23A and mHR23B are not known. Here, we present a mouse model for mHR23B. Unlike XPC-deficient cells, mHR23B(-/-) mouse embryonic fibroblasts are not UV sensitive and retain the repair characteristics of wild-type cells. In agreement with the results of in vitro repair studies, this indicates that mHR23A can functionally replace mHR23B in NER. Unexpectedly, mHR23B(-/-) mice show impaired embryonic development and a high rate (90%) of intrauterine or neonatal death. Surviving animals display a variety of abnormalities, including retarded growth, facial dysmorphology, and male sterility. Such abnormalities are not observed in XPC and other NER-deficient mouse mutants and point to a separate function of mHR23B in development. This function may involve regulation of protein stability via the ubiquitin/proteasome pathway and is not or only in part compensated for by mHR23A.

Animals↗