Assignment of a Chinese xeroderma pigmentosum patient from Taiwan to complementation group C

A 2 years and 7 months-old Chinese boy with severe skin symptoms was diagnosed as xeroderma pigmentosum (XP) at Chang Gung Memorial Hospital in Taipei, Taiwan. Skin fibroblasts derived from the patient (patient identification number, XP1CTA) were used for genetic complementation analysis by the conventional cell-fusion technique followed by measurement of ultraviolet light (UV)-induced unscheduled DNA synthesis (UDS). The level of UDS in XP1CTA cells measured by autoradiography was about 20% of that in normal cells. When XP1CTA cells were fused with cells of a representative strain from each of the complementation groups A, D, E, F, G, and H, binuclear cells showed UDS levels in the range of normal cells, demonstrating a clear complementation between XP1CTA strain and either one of these strains. XP1CTA cells failed to complement with all the five reference strains belonging to group C. From these results, the XP1CTA was unambiguously assigned to complementation group C. Sensitivity of XP1CTA cells to UV, as measured by colony-forming ability, also fell within a range of variation in UV sensitivities of these group C XP cell strains.