Understanding Xeroderma Pigmentosum Complementation Groups Using Gene Expression Profiling after UV-Light Exposure.

Children with the recessive genetic disorder Xeroderma Pigmentosum (XP) have extreme sensitivity to UV-light, a 10,000-fold increase in skin cancers from age 2 and rarely live beyond 30 years. There are seven genetic subgroups of XP, which are all resultant of pathogenic mutations in genes in the nucleotide excision repair (NER) pathway and a XP variant resultant of a mutation in translesion synthesis, POLH. The clinical symptoms and severity of the disease is varied across the subgroups, which does not correlate with the functional position of the affected protein in the NER pathway. The aim of this study was to further understand the biology of XP subgroups, particularly those that manifest with neurological symptoms. Whole genome gene expression profiling of fibroblasts from each XP complementation group was assessed before and after UV-light exposure. The biological pathways with altered gene expression after UV-light exposure were distinct for each subtype and contained oncogenic related functions such as perturbation of cell cycle, apoptosis, proliferation and differentiation. Patients from the subgroups XP-B and XP-F were the only subgroups to have transcripts associated with neuronal activity altered after UV-light exposure. This study will assist in furthering our understanding of the different subtypes of XP which will lead to better diagnosis, treatment and management of the disease.