Elsevier

DNA Repair

Volume 8, Issue 1, 1 January 2009, Pages 114-125
DNA Repair

XPC initiation codon mutation in xeroderma pigmentosum patients with and without neurological symptoms

https://doi.org/10.1016/j.dnarep.2008.09.007Get rights and content

Abstract

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 (∼30 kBP), 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.

Introduction

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder caused by a defect in the nucleotide excision repair (NER) pathway [1], [2], [3], [4] which removes a wide spectrum of structurally unrelated DNA lesions including cyclobutane pyrimidine dimers (CPD) and 6-4 photoproducts induced by ultraviolet radiation (UV) from sunlight. Cells from XP patients fall into seven genetic complementation groups XP-A through XP-G, corresponding to seven of the gene products involved in NER and a variant form with a defect in trans-lesion polymerase eta. XP patients have increased freckle-like pigmentation in response to sun exposure and a greater than 1000-fold increased incidence of UV-induced skin cancers at an early age [4], [5].

XP complementation group C (XP-C) is one of the more common forms in the United States [6]. Cells from XP-C patients have proficient transcription coupled nucleotide excision repair (TCR) but defective global genome nucleotide excision repair (GGR) of damaged DNA while cells from XP complementation groups A, B, D, F and G are defective in both GGR and TCR [3]. The XPC DNA repair gene encodes a 940 amino acid protein that forms an in vivo stable heterotrimeric complex with one of the two human orthologs of Saccharomyces cerevisiae Rad23p (RAD23A or RAD23B) and centrin 2, a component of the centrosome, and functions as a DNA-damage sensor and repair recruitment factor in GGR [3], [7], [8].

About 20% of XP patients exhibit progressive neurodegeneration [4], [9]. However, neurological symptoms are rarely seen in XP-C patients. Most of the XP patients with neurological symptoms are in XP complementation groups XP-A, XP-B, XP-D or XP-G [2], [6]. Since the development of neurologic involvement has grave clinical prognostic implications, understanding the relationship between complementation group and neurologic degeneration is extremely important. We report here two XP patients (XP21BE and XP329BE) with the same homozygous initiation codon mutation in the XPC gene. While both patients have multiple skin cancers, XP21BE has developmental delay and sensorineural hearing loss while XP329BE has no neurological abnormalities. The neurological abnormalities in XP21BE may not be related to the XPC gene defect.

Section snippets

Patients

After obtaining informed consent, the XP patients were studied at the Clinical Center, NIH under protocols approved by the NCI Institutional Review Board. Both patients had thorough skin examinations and biopsy of lesions suspicious for skin cancer. Examinations included detailed ophthalmology, neurology, audiology, and other assessments as medically indicated.

Cell lines, culture conditions and DNA/RNA isolation

Fibroblast and lymphoblastoid cell cultures from two XP-C families were studied: Family A: XP21BE (GM09943, GM09942); Family B: XP329BE

Clinical findings

Both patient XP21BE (Fig. 1A) and patient XP329BE (Fig. 1B) had a history of lentiginous hyperpigmentation in sun exposed areas before the first year of age and did not have the acute photosensitivity with blistering burns after brief sun exposure which is present in some XP patients (Table 1). Both patients began to develop skin cancers by age 3 years.

Patient XP21BE

By age 13 years patient XP21BE had 2 basal cell carcinomas and 33 squamous cell carcinomas. By age 27 years she had a total of 7 basal cell

XPC initiation codon mutation, DNA repair and skin cancers

Most of the mutations reported in the XPC gene in cells from XP patients create premature termination codons [10], [20], [23], [24], [25], [26], [27], [28]. PTCs can reduce the levels of XPC message and XPC protein in cells by means of nonsense-mediated mRNA decay (NMD) [29]. Only two missense mutations in the XPC gene have been reported. These are Pro334His [25] and Trp690Ser [23], which alters the stability of the encoded mutant protein [30]. Splice site mutations may result in severe or mild

Conflict of interest

None declare.

Acknowledgments

This research was supported by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research. We are grateful to the patients and their families for their cooperation in this research. S.E. was supported in part by a grant from the Deutsche Forschungsgemeinschaft DFG (EM 63/1-1).

References (46)

  • A. Rivera-Begeman et al.

    A novel XPC pathogenic variant detected in archival material from a patient diagnosed with Xeroderma Pigmentosum: a case report and review of the genetic variants reported in XPC

    DNA Repair (Amst.)

    (2007)
  • H. Slor et al.

    Clinical, cellular, and molecular features of an Israeli Xeroderma Pigmentosum Family with a Frameshift Mutation in the XPC gene: sun protection prolongs life

    J. Invest. Dermatol.

    (2000)
  • M. Kozak

    Initiation of translation in prokaryotes and eukaryotes

    Gene

    (1999)
  • A. Tapias et al.

    Ordered conformational changes in damaged DNA induced by nucleotide excision repair factors

    J. Biol. Chem.

    (2004)
  • K.H. Kraemer et al.

    Genome instability, DNA repair and cancer

  • T.M. Ruenger et al.

    Hereditary diseases of genome instability and DNA repair

  • E.C. Friedberg et al.

    DNA Repair and Mutagenesis

    (2006)
  • K.H. Kraemer et al.

    Xeroderma pigmentosum. Cutaneous, ocular, and neurologic abnormalities in 830 published cases

    Arch. Dermatol.

    (1987)
  • K.H. Kraemer et al.

    The role of sunlight and DNA repair in melanoma and nonmelanoma skin cancer: the xeroderma pigmentosum paradigm

    Arch. Dermatol.

    (1994)
  • S. Moriwaki et al.

    Xeroderma pigmentosum—bridging a gap between clinic and laboratory

    Photodermatol. Photoimmunol. Photomed.

    (2001)
  • S.G. Khan et al.

    The human XPC DNA repair gene: arrangement, splice site information content and influence of a single nucleotide polymorphism in a splice acceptor site on alternative splicing and function

    Nucleic Acids Res.

    (2002)
  • R. Legerski et al.

    Expression cloning of a human DNA repair gene involved in xeroderma pigmentosum group C

    Nature

    (1992)
  • S.G. Khan et al.

    Reduced XPC DNA repair gene mRNA levels in clinically normal parents of xeroderma pigmentosum patients

    Carcinogenesis

    (2006)

    • Cited by (35)

    • Unusual intraoral cancer with unexpected outcome in a patient with xeroderma pigmentosum: An alert for antineoplastic treatment

      2020, Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology
      Citation Excerpt :

      However, in patients with XP, who are potential carriers of defective XP-C,20 this mechanism of reversal of damage caused by chemotherapy in normal cells is compromised, and thus, normal cells may also undergo apoptosis. Depending on the degree of disability of XP-C20 and the resulting number of lost cells, cisplatin can cause death, especially as a result of renal failure because the urinary tract is the main route of drug elimination.33 Thus, XP-C would represent an important biomarker, not only for cancer prevention and diagnosis but also to guide treatment.

    • Oxidative and energy metabolism as potential clues for clinical heterogeneity in nucleotide excision repair disorders

      2015, Journal of Investigative Dermatology
      Citation Excerpt :

      Indeed, a very recent work associated the expression of XPC variants with the younger age at onset of Huntington disease (Berger et al., 2013), a neurodegenerative disease that has been linked with oxidative DNA damage and stress responses (Stack et al., 2008). However, neurological degeneration is very rare in XP-C patients, and only two patients with neurological abnormalities have been yet diagnosed (Bernardes de Jesus et al., 2008; Khan et al., 2009). With regard to the role of XPA in cellular responses to oxidative stress, real-time quantification of superoxide and nitric oxide derivatives released by a living cell indicated that XP-A fibroblasts provide larger oxidative bursts than control cells (Arbault et al., 2004).

    • Cockayne syndrome pathogenesis: Lessons from mouse models

      2013, Mechanisms of Ageing and Development
      Citation Excerpt :

      GG-NER, which can be measured by UV damage-induced, non-S phase DNA repair synthesis (termed unscheduled DNA synthesis, UDS (Nakazawa et al., 2010)), is unaltered in CS, but is deficient in xeroderma pigmentosum (XP). XP is another rare recessive genetic photosensitivity syndrome characterized by sun-induced pigmentation abnormalities, a >1000 fold increased skin cancer risk, and in some patients accelerated neurodegeneration but in contrast to CS largely normal development (Khan et al., 2009; Soufir et al., 2010). In contrast to XP, CS patients do not show cancer predisposition, implying that TC-NER is not required for preventing cancer (Hoeijmakers, 2009).

    • Preclinical corrective gene transfer in xeroderma pigmentosum human skin stem cells

      2012, Molecular Therapy
      Citation Excerpt :

      Grafting genetically corrected skin in XP patients would certainly reduce the incidence of cancerous lesions as long as (i) skin grafts contain a sufficient proportion of stem cells to allow lifelong renewal of the regenerated epidermis, (ii) all stem cells are functionally corrected, i.e., are protected against mutagenesis, (iii) safety assessment excludes adverse effects such as oncogene activation linked to retroviral integration. XP group C (XP-C) is the best candidate for an ex vivo cutaneous gene therapy protocol since clinical traits of XP-C patients are mainly restricted to photo-exposed skin, generally without the neurological disorders that can be observed in other XP groups.14 In our previous attempt, however, we failed to obtain a sustained expression of XPC complementary DNA in XP-C primary keratinocytes, i.e., for more than 30 PD (ref. 15 and Arnaudeau, Chevallier and Magnaldo, unpublished results).

    • Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression

      2023, Brain

    • Clinical and molecular characterization of Xeroderma pigmentosum in Moroccan population: a case series of 40 patients

      2022, Egyptian Journal of Medical Human Genetics
    View all citing articles on Scopus
    1

    Present address: Department of Dermatology, University of Goettingen, Germany.

    View full text
    Published by Elsevier B.V.