Abstract
Nucleotide excision repair (NER) is a DNA repair pathway, which eliminates various helix-distorting DNA damage including some oxidative damage and UV-induced (6-4) photoproducts (6-4PPs). Here, to get clues to understand why patients with NER-defective disorders develop progressive neurological abnormalities, NER capabilities in neural cells were investigated. Primary neurons and astrocytes from rat embryonic brains were prepared in mixed-cell cultures, and fibroblasts from the same embryos were cultured for comparison. The original method for in situ 6-4PP determination using antibodies against the lesion was applied to determine NER capabilities in individual neural cells, which were identified by staining of specific cell markers. The results demonstrated that NER pathway is functional in both neurons and astrocytes, but their repair capabilities are significantly lower than that of fibroblasts. The degree of DNA repair deficiency was comparable to the case of NER-defective human fibroblasts (TTD2VI) that expressed only half levels of NER proteins (TFIIH) of normal cells. Consistent with these results, the levels of an NER protein (PCNA) recruited at localized UV damage sites were apparently lower in neurons and astrocytes than those in fibroblasts. Thus, the present study suggests that the neural cells constituting the central nervous system may generally have the attenuated NER capabilities because of reduced expression of NER proteins.
