HIGH PREVALENCE OF THE POINT MUTATION IN EXON-6 OF THE XERODERMA-PIGMENTOSUM GROUP-A-COMPLEMENTING (XPAC) GENE IN XERODERMA-PIGMENTOSUM GROUP-A PATIENTS IN TUNISIA

Xeroderma pigmentosum (XP) patients in Tunisia who belong to the genet ic complementation group A (XPA) have milder skin symptoms than do Jap anese XPA patients. Such difference in the clinical features might be caused by the difference in the site of mutation in the XP A-complemen ting (XPAC) gene. The purpose of this study is to identify the genetic alterations in the XPAC gene in the Tunisian XPA patients and to inve stigate the relationship between the clinical symptoms and the genetic alterations. Three sites of mutation in the XPAC gene have been ident ified in the Japanese XPA patients, and about 85% of them have a G-->C point mutation at the splicing acceptor site of intron 3. We found th at six (86%) of seven Tunisian XPA patients had a nonsense mutation in codon 228 in exon 6, because of a CGA-->TGA point mutation, which can be detected by the HphI RFLP. This type of mutation is the same as th ose found in two Japanese XPA patients with mild clinical symptoms. Mi lder skin symptoms in the XPA patients in Tunisia than in those in Jap an, despite mostly sunny weather and the unsatisfactory sun protection in Tunisia, should be due to the difference in the mutation site.