Genetic investigation of XPA gene: high frequency of the c.682C>T mutation in Moroccan XP patients with moderate clinical profile

Generation of XPA p.Arg228T mutant LUMCi004-A cell line for modeling Xeroderma pigmentosum group A

Xeroderma pigmentosum group A (XPA) is an inherited skin disorder characterized by sensitivity to ultraviolet radiation. In Maghrebi patients, a homozygous mutation in exon 6 of the XPA gene (c.682C>T) results in the introduction of a premature termination codon. Using CRISPR/Cas9-mediated gene editing, this mutation was introduced into the well-characterized LUMCi004-A line. The resulting hiPSC line showed typical morphology, expressed markers of the undifferentiated state, was able to differentiate into the three germ layers in vitro and displayed a normal karyotype. When paired with its isogenic counterpart, this line represents a valuable resource to model the disease.

Evaluation of the effectiveness and safety of combined oral and topical photoprotection with a standardized extract of Polypodium leucotomos (Fernblock®) in a Moroccan population with xeroderma pigmentosum

BACKGROUND

Xeroderma pigmentosum (XP) is a rare autosomal-recessive genodermatosis resulting from a DNA-repair defect syndrome. The purpose was to evaluate the prevention on new malignant lesions in patients taking a supplement with Fernblock® (Polypodium leucotomos extract [PLE]) and secondarily correlation with the photoprotective behavior.

METHODS

A prospective, single-center and open cohort study was conducted over a 12-month period. The study was performed in Morocco. Optimal photoprotection behavior was recommended. Patients were instructed to take one capsule containing 480 mg of Fernblock® and 5 mcg vitamin D and to apply sunscreen with a SPF50+ and Fernblock® every 2 h during sun exposure. The demographic, clinical, and dermatoscopic patient data were collected at baseline (T0) and following visits at 3 months (T3), 6 months (T6), and 12 months (T12) when it was assessed: Investigator Global Assessment (IGA), Patient/Guardian Global Assessment (PGA), Patient/Guardian Satisfaction Questionnaire, and Photographic and Adverse Events Registration. Pertinent statistical study was performed.

RESULTS

Eighteen patients completed the study. Eleven patients (61%) finished the study without new lesions. Seven patients developed new lesions by the end of the study. Among them, only 30% showed an ideal photoprotective behavior. The lack of an optimal photoprotective behavior increased the probability of developing lesions by 2.5 times with 95% confidence interval.

CONCLUSIONS

In our study, more than 60% of patients taking a supplement with Fernblock® did not develop new lesions, and furthermore, we detected that patients following almost ideal photoprotection were 2.5 times less likely to develop NMSC lesions.

Case Report: Identification of a Heterozygous XPA c.553C>T Mutation Causing Neurological Impairment in a Case of Xeroderma Pigmentosum Complementation Group A

We aimed to determine if an adolescent patient presenting with neurological impairment has xeroderma pigmentosum (XP). For this purpose, whole-exome sequencing was performed to assess mutations in XP genes. Dermal fibroblasts were established from a skin biopsy and XPA expression determined by immunoblotting. Nucleotide excision repair (NER) capacity was measured by detection of unscheduled DNA synthesis (UDS) in UVC-irradiated patient fibroblasts. Genetic analysis revealed two recessive mutations in XPA, one known c.682C>T, p.Arg228Ter, and the other c.553C>T, p.Gln185Ter, only two cases were reported. XPA protein was virtually undetectable in lysates from patient-derived fibroblast. The patient had significantly lower UV-induced UDS (3.03 ± 1.95%, p < 0.0001) compared with healthy controls (C5RO = 100 ± 12.2; C1UMN = 118 ± 5.87), indicating significant NER impairment. In conclusion, measurement of NER capacity is beneficial for the diagnosis of XP and in understanding the functional impact of novel mutations in XP genes. Our findings highlight the importance of neurologists considering XP in their differential diagnosis when evaluating patients with atypical neurodegeneration.

Identification of a ERCC5 c.2333T>C (L778P) Variant in Two Tunisian Siblings With Mild Xeroderma Pigmentosum Phenotype

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder due to a defect in the nucleotide excision repair (NER) DNA repair pathway, characterized by severe sunburn development of freckles, premature skin aging, and susceptibility to develop cancers at an average age of eight. XP is an example of accelerated photo-aging. It is a genetically and clinically heterogeneous disease. Eight complementation groups have been described worldwide. In Tunisia, five groups have been already identified. In this work, we investigated the genetic etiology in a family with an atypically mild XP phenotype. Two Tunisian siblings born from first-degree consanguineous parents underwent clinical examination in the dermatology department of the Charles Nicolle Hospital on the basis of acute sunburn reaction and mild neurological disorders. Blood samples were collected from two affected siblings after written informed consent. As all mutations reported in Tunisia have been excluded using Sanger sequencing, we carried out mutational analysis through a targeted panel of gene sequencing using the Agilent HaloPlex target enrichment system. Our clinical study shows, in both patients, the presence of achromic macula in sun exposed area with dermatological feature suggestive of Xeroderma pigmentosum disease. No developmental and neurological disorders were observed except mild intellectual disability. Genetic investigation shows that both patients were carriers of an homozygous T to C transition at the nucleotide position c.2333, causing the leucine to proline amino acid change at the position 778 (p.Leu778Pro) of the ERCC5 gene, and resulting in an XP-G phenotype. The same variation was previously reported at the heterozygous state in a patient cell line in Europe, for which no clinical data were available and was suggested to confer an XP/CS phenotype based on functional tests. This study contributes to further characterization of the mutation spectrum of XP in consanguineous Tunisian families and is potentially helpful for early diagnosis. It also indicates that the genotype-phenotype correlation is not always coherent for patients with mild clinical features. These data therefore suggest that targeted NGS is a highly informative diagnostic strategy, which can be used for XP molecular etiology determination.