Uncommon nucleotide excision repair phenotypes revealed by targeted high-throughput sequencing

Area of Science:

• Genetics
• Molecular Biology
• Medical Diagnostics

Background:

• Nucleotide excision repair (NER) deficiency underlies genetic disorders such as xeroderma pigmentosum (XP) and Cockayne syndrome (CS).
• These conditions present with overlapping phenotypes and involve numerous genes, complicating diagnosis.
• A novel diagnostic strategy was developed focusing on 16 NER-related genes using multiplex amplification and next-generation sequencing (NGS).

Purpose of the Study:

• To establish a new diagnostic approach for NER-related disorders.
• To evaluate the efficacy of multiplex amplification coupled with NGS for genetic analysis.
• To identify causative mutations in patients with XP, CS, and related conditions.

Main Methods:

• Enrichment of 16 NER-related genes via multiplex amplification.
• Next-generation sequencing (NGS) performed on the Ion Torrent PGM platform.
• Analysis of a test cohort (11 samples) and a prospective cohort (40 patients).

Main Results:

• Causative mutations were identified in 43% (17/40) of prospective patients.
• Mutations in ERCC6 (CSB) and ERCC8 (CSA) were found in patients with classical, mild, or incomplete CS phenotypes.
• A founder mutation in POLH (XP-variant) was identified in Basque XP patients; ERCC2, ERCC3, and ERCC5 mutations were linked to UV-sensitive syndrome and mixed XP/CS phenotypes.

Conclusions:

• NGS is an effective method for molecular analysis of NER-related disorders.
• Targeted NGS is particularly valuable for diagnosing atypical presentations, including mild or combined phenotypes.
• Combining NGS with functional tests and clinical evaluation enables rapid, cost-effective diagnosis of NER defects.