EXPRESSION OF THE EXCISION-REPAIR GENE, ERCC3 (EXCISION-REPAIR CROSS-COMPLEMENTING), DURING MOUSE DEVELOPMENT

Expression of the human ERCC3 (excision repair cross-complementing) ge ne in cells from patients with xeroderma pigmentosum (XP) group B (XP- B) corrects the defect in repair of UV light-induced DNA damage. XP-B is one of three groups of XP which exhibit the clinical symptoms of bo th XP and Cockayne's Syndrome (CS). CS and XP-B/CS patients develop se vere neurological dysfunction during development. In order to explore the link between the defective gene and the neurological deficits in X P/CS, we have studied the expression of ERCC3 mRNA in developing mice by in situ hybridisation. ERCC3 was found to be ubiquitously expressed in cells from all regions and all developmental stages, from 9 day po st-coitum embryo, to 15 day post-natal brain. In post-natal brain, reg ional differences in expression correlated with cell density and there was no evidence of cell specific or developmental alterations in leve ls of expression. These results indicate that the constitutively expre ssed gene does not perform a discrete developmental function. The neur ological defects apparent in XP-B are likely to arise pleiotypically f rom the participation of ERCC3 in interactions with other elements inv olved in particular aspects of neurodevelopmental control. These resul ts emphasise the developmental importance of genes whose primary funct ions are apparently unconnected with development.