Khan, SG, Oh, KS, Emmert, S, Imoto, K, Tamura, D, Digiovanna, JJ et al.. XPC initiation codon mutation in xeroderma pigmentosum patients with and without neurological symptoms. DNA Repair (Amst) 8: 114-125

Basic Research Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States.
DNA Repair (Impact Factor: 3.11). 11/2008; 8(1):114-25. DOI: 10.1016/j.dnarep.2008.09.007
Source: PubMed


Two unrelated xeroderma pigmentosum (XP) patients, with and without neurological abnormalities, respectively, had identical defects in the XPC DNA nucleotide excision repair (NER) gene. Patient XP21BE, a 27-year-old woman, had developmental delay and early onset of sensorineural hearing loss. In contrast, patient XP329BE, a 13-year-old boy, had a normal neurological examination. Both patients had marked lentiginous hyperpigmentation and multiple skin cancers at an early age. Their cultured fibroblasts showed similar hypersensitivity to killing by UV and reduced repair of DNA photoproducts. Cells from both patients had a homozygous c.2T>G mutation in the XPC gene which changed the ATG initiation codon to arginine (AGG). Both had low levels of XPC message and no detectable XPC protein on Western blotting. There was no functional XPC activity in both as revealed by the failure of localization of XPC and other NER proteins at the sites of UV-induced DNA damage in a sensitive in vivo immunofluorescence assay. XPC cDNA containing the initiation codon mutation was functionally inactive in a post-UV host cell reactivation (HCR) assay. Microsatellite markers flanking the XPC gene showed only a small region of identity ( approximately 30kBP), indicating that the patients were not closely related. Thus, the initiation codon mutation resulted in DNA repair deficiency in cells from both patients and greatly increased cancer susceptibility. The neurological abnormalities in patient XP21BE may be related to close consanguinity and simultaneous inheritance of other recessive genes or other gene modifying effects rather than the influence of XPC gene itself.

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    • "For instance, although most XP-V, XP-C and XP-E patients (which represent in Europe and the United States 40–58% of all XP cases) lack severe sunburn reactions, some cases display extreme phenotypes [2], [14], [15]. Mutations in XPC and XPE subtypes, which usually do not lead to neurological disease, can present central nervous system abnormalities due genetic and environmental modifier factors [2], [16], [17]. XPV patients (who are rarely affected by neurological abnormalities) can exhibit skin injuries that vary considerably in severity [18]. "
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    ABSTRACT: Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder characterized by extreme sensitivity to actinic pigmentation changes in the skin and increased incidence of skin cancer. In some cases, patients are affected by neurological alterations. XP is caused by mutations in 8 distinct genes (XPA through XPG and XPV). The XP-V (variant) subtype of the disease results from mutations in a gene (XPV, also named POLH) which encodes for Polη, a member of the Y-DNA polymerase family. Although the presence and severity of skin and neurological dysfunctions differ between XP subtypes, there are overlapping clinical features among subtypes such that the sub-type cannot be deduced from the clinical features. In this study, in order to overcome this drawback, we undertook whole-exome sequencing in two XP sibs and their father. We identified a novel homozygous nonsense mutation (c.897T>G, p.Y299X) in POLH which causes the disease. Our results demonstrate that next generation sequencing is a powerful approach to rapid determination of XP genetic etiology.
    Full-text · Article · Jun 2013 · PLoS ONE
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    • "However, two patients were reported to be homozygous for the delTG but with neurological involvement (Soufir et al., 2010). This is similar to XP-C patients reported with homozygous mutations in the initiation codon with and without neurological involvement (Khan et al., 2009). These data suggest that neurological involvement may be caused by consanguinity with homozygosity of other unknown genes or by modifying genes or prenatal exposure to teratogens or infectious agents. "
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    ABSTRACT: In this issue, Soufir et al. report a founder mutation in the XPC DNA repair gene in 74% of families with xeroderma pigmentosum (XP) in the Maghreb region (Algeria, Morocco, and Tunisia) of northern Africa. These patients have a high frequency of skin cancer. The presence of this founder mutation provides an opportunity for genetic counseling and early diagnosis of XP.
    Preview · Article · Jun 2010 · Journal of Investigative Dermatology
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    • "Two patients carrying this mutation had neurological signs, which were for one patient indistinguishable from those observed in XP-A patients. Neurological impairment was recently described in a consanguineous XP-C family harboring a homozygous mutation in the initiation codon of XPC, whereas neurological symptoms were absent in another family carrying the same mutation (Khan et al., 2009). "
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    ABSTRACT: Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder that is associated with an inherited defect of the nucleotide excision repair pathway (NER). In this study, we investigated the involvement of XP genes in 86 XP patients belonging to 66 unrelated families, most of them consanguineous and originating from Maghreb. Sequencing analysis was performed either directly (44 probands) or after having previously characterized the involved XP gene by complementation assay (22 families). XPC and XPA mutations were respectively present in 56/66 and 8/66 probands. Strikingly, we identified the same homozygous frameshift mutation c.1643_1644delTG (p.Val548AlafsX25) in 87% of XP-C patients. Haplotype analysis showed a common founder effect for this mutation in the Mediterranean region, with an estimated age of 50 generations or 1,250 years. Among 7/8 XP-A patients, we found the previously reported nonsense homozygous XPA mutation (p.Arg228X). Six mutations--to our knowledge previously unreported--(five in XPC, one in XPA) were also identified. In conclusion, XPC appears to be the major disease-causing gene concerning xeroderma pigmentosum in North Africa. As the (p.Val548AlafsX25) XPC mutation is responsible for a huge proportion of XP cases, our data imply an obvious simplification of XP molecular diagnosis, at least in North Africa.
    Full-text · Article · Jun 2010 · Journal of Investigative Dermatology
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