ABSTRACT: Cockayne syndrome (CS) is a rare genetic disease characterized by severe growth, mental retardation and pronounced cachexia. CS is most frequently due to mutations in either of two genes, CSB and CSA. Evidence for a role of CSB protein in the repair of oxidative DNA damage has been provided recently. Here, we show that CSA is also involved in the response to oxidative stress. CS-A human primary fibroblasts and keratinocytes showed hypersensitivity to potassium bromate, a specific inducer of oxidative damage. This was associated with inefficient repair of oxidatively induced DNA lesions, namely 8-hydroxyguanine (8-OH-Gua) and (5'S)-8,5'-cyclo 2'-deoxyadenosine. Expression of the wild-type CSA in the CS-A cell line CS3BE significantly decreased the steady-state level of 8-OH-Gua and increased its repair rate following oxidant treatment. CS-A cell extracts showed normal 8-OH-Gua cleavage activity in an in vitro assay, whereas CS-B cell extracts were confirmed to be defective. Our data provide the first in vivo evidence that CSA protein contributes to prevent accumulation of various oxidized DNA bases and underline specific functions of CSB not shared with CSA. These findings support the hypothesis that defective repair of oxidative DNA damage is involved in the clinical features of CS patients.
Oncogene 07/2007; 26(30):4336-43. · 6.37 Impact Factor
ABSTRACT: Disseminated superficial actinic porokeratosis (DSAP) is the most common porokeratosis and is characterized by multiple keratotic lesions which tend to occur at sun-exposed sites. A mild hypersensitivity to X-rays has been reported for DSAP-derived fibroblasts and frequent over-expression of p53 has been found in lesional epidermis.
In order to clarify whether genome maintenance mechanisms might be compromised in this disease the following approaches were undertaken: (i) primary cultured keratinocytes and fibroblasts from DSAP patients were characterized for ultraviolet (UV) B and X-ray response; (ii) 15 lesions were studied for p53 mutations, and (iii) the differentiation status of DSAP-derived keratinocytes was evaluated.
Primary cultures of keratinocytes and fibroblasts were established from lesional and nonlesional skin biopsies of two subjects with DSAP. p53 mutations were analysed by DNA sequencing of the conserved region of the TP53 gene. Differentiation was evaluated both in stratified epithelial sheets from confluent keratinocyte cultures and in organotypic skin cultures.
The cytotoxic and apoptotic response to UVB or X-irradiation was similar in DSAP-derived keratinocytes and fibroblasts when compared with normal cells. Two of 15 lesions examined presented p53 mutations located at nondipyrimidine sites. A strikingly decreased expression of filaggrin was observed both in reconstructed epidermis and in reconstructed skin.
The UVB and X-ray response of DSAP-derived keratinocytes and fibroblasts indicates that the actinic character of this skin pathology is not due to radiation hypersensitivity. In agreement with this finding, mutations in the p53 gene, which are often associated with UV-related skin carcinogenesis, were rarely detected in DSAP lesions and were not UV-specific. Reconstructed epidermis and reconstructed skin models successfully reproduced the main features of this genodermatosis, showing that DSAP-derived keratinocytes bear an inherent defect in the terminal differentiation programme.
British Journal of Dermatology 02/2004; 150(1):47-55. · 3.67 Impact Factor
Cell Death and Differentiation 07/2003; 10(6):754-6. · 8.85 Impact Factor