Simplifying Detection of Copy-Number Variations in Maturity-Onset Diabetes of the Young

Area of Science:

• Genomics
• Molecular Biology
• Bioinformatics

Background:

• Copy-number variations (CNVs) are large DNA deletions or duplications.
• Traditional methods for CNV detection include microarray-based genomic hybridization and multiplex ligation probe amplification.
• Next-generation sequencing (NGS) coupled with advanced bioinformatics offers a novel approach for CNV detection.

Observation:

• Maturity-onset diabetes of the young (MODY) 5, an autosomal-dominant diabetes subtype, is frequently caused by heterozygous deletions of the HNF1B gene on chromosome 17q12.
• This study re-examined NGS data from 57 patients with suspected MODY who were negative for pathogenic mutations via targeted panels.
• A CNV calling tool was employed to analyze the NGS data for potential 17q12 deletions.

Findings:

• Whole-gene deletions within HNF1B (1.46–1.85 Mbp) were identified in three individuals presenting with MODY 5 features.
• These deletions were confirmed to be part of a broader 17q12 deletion syndrome through independent validation methods.
• Two additional patients with 17q12 deletions were diagnosed using this bioinformatic approach.

Implications:

• Large-scale deletions are the predominant cause of MODY 5.
• Direct detection of these deletions from NGS data is feasible, eliminating the need for supplementary diagnostic techniques.
• This bioinformatic strategy enhances the diagnostic yield for MODY 5 and related 17q12 deletion syndromes.