In CSA-/- cells, the interruption of the gene sequencein exon 2 of the Ercc8 gene results in protein absence (van der Horst et al., 2002).When exposed to UV, the fibroblasts of these animals manifest higher UV sensitivity,and they have an inability to resume RNA synthesis and defective TC-NER, these beingthe classic characteristic of CS (Lehmann,1982; van der Horst etal., 1997, 2002). This evidence concerns the gene ERCC8 and Cowden syndrome 1.