Diagnosis of xeroderma pigmentosum patients and carriers by PCR-RFLP analysis

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The gene responsible for xeroderma pigmentosum (XP) group A has recently been cloned and designated XPA gene. Previous studies have shown that most Japanese XPA patients have homozygous mutations for the splicing site of intron 3 of the XPA gene, which was recognized by restriction endonuculease (RE) AlwNI (AlwNI mutation). Other mutations found to data have been the nonsense mutation at codon 228 in exon 6, recognized by RE HphI (HphI mutation), and at codon 116 in exon 3, recognized by RE MseI (MseI mutation) . Using polymerase chain reaction restriction fragment length polymorphism (PCR-PFLP) analysis, we examined the point mutations of the XPA gene.(1) We found that 12 patients of 17 patients were homozygous for the AlwNI mutation, four were compound heterozygotes for the AlwNI mutation and the HphI mutation, and one was a compound heterozygote for the AlwNI mutation and the MseI mutation. Investigation of their clinical features suggested that the four patients with HphI mutation … More had milder clinical manifestations. PCR-RFLP analysis of the XPA gene in the three asymptomatic siblings of the XPA patients revealed that two were carriers of the mutated XPA allele, and one was not a carrier.(2) We found two siblings with XP group A who showed a significant difference in clinical manifestations and younger sister was much milder. The elder sister started strict sun protection at 4 years of age, whereas the younger began at 2 years of age. PCR-RFLP analysis revealed that both patients had the identical mutation in XPA gane. These data suggent, that in patients with XP the earlier sun protection begins had the later skin cancer develops.(3) We diagnosed the XPA gene mutation of a fetus whose sibling is a XPA patient. PCR-RFLP analysis of DNA from amniotic fluid showed the homozygous mutation.(4) P53 protein is critical for DNA damage repair, cell cycle and apoptosis. The p53 protein induction by UVB in XPA cells with various gene mutations was examined using western blot analysis. Cells with HphI/AlwNI heterozygous mutations showed weaker induction of p53 protein by UVB than cells with AlwNI homozygous mutations or AlwNI/MseI heterozygous mutations. Less