MOLECULAR ANALYSIS OF MUTATIONS IN THE CSB (ERCC6) GENE IN PATIENTS WITH COCKAYNE-SYNDROME

Cockayne syndrome is a multisystem sun-sensitive genetic disorder asso ciated with a specific defect in the ability to perform transcription- coupled repair of active genes after UV irradiation. Two complementati on groups (CS-A and CS-B) have been identified, and 80% of patients ha ve been assigned to the CS-B complementation group. We have analyzed t he sites of the mutations in the CSB gene in 16 patients, to determine the spectrum of mutations in this gene and to see whether the nature of the mutation correlates with the type and severity of the clinical symptoms. In nine of the patients, the mutations resulted in truncated products in both alleles, whereas, in the other seven, at least one a llele contained a single amino acid change. The latter mutations were confined to the C-terminal two-thirds of the protein and were shown to be inactivating by their failure to restore UV-irradiation resistance to hamster UV61 cells, which are known to be defective in the CSB gen e. Neither the site nor the nature of the mutation correlated with the severity of the clinical features. Severe truncations were found in d ifferent patients with either classical or early-onset forms of the di sease.