Genetic complementation analysis of xeroderma pigmentosum.

To characterize the mutations in different unrelated xeroderma pigmentosum (XP) patients, a complementation test was performed using the technique of somatic cell hybridization. DNA repair following UV exposure was studied in multinuclear cells resulting from fusions between in vitro cultivated cells from different patients. The parental XP cells performed low or negligible levels of repair DNA synthesis, whereas in some combinations binuclear hybrid cells showed repair DNA synthesis as a result of complementation. The results indicate the presence of five different complementation groups in XP.