Mitochondrial sequence variation in African-American primary open-angle glaucoma patients

Area of Science:

• Ophthalmology
• Genetics
• Mitochondrial Biology

Background:

• Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness, disproportionately affecting African-Americans.
• Mitochondrial dysfunction and genetic variations in mitochondrial DNA (mtDNA) are hypothesized contributors to POAG pathogenesis.
• Previous research suggested a higher incidence of novel, potentially pathogenic mtDNA variations in POAG patients.

Purpose of the Study:

• To analyze the spectrum of mtDNA sequence variations in African-American POAG patients.
• To determine if novel, nonsynonymous, transversional, or pathogenic mtDNA variations occur more frequently in POAG cases compared to controls.
• To assess the role of novel mtDNA mutations in the high susceptibility of African-Americans to POAG.

Main Methods:

• Deep sequencing of a single 16,487 base pair PCR amplicon from mtDNA of 22 African-American POAG cases and 22 age-matched controls using Ion Torrent technology.
• Validation of candidate novel variants through Sanger sequencing.
• Classification and interpretation of sequence variants utilizing the MITOMAP database.

Main Results:

• Over 99.8% of identified sequence variations were previously reported.
• The observed ratio of novel variants to POAG cases was sevenfold lower than prior estimates.
• Novel mtDNA variants were found in only 3 of 22 cases, novel nonsynonymous changes in 1 of 22, and novel transversions in 0 of 22, with no significant difference from controls (p<.0005, p<.0004, p<.0001).

Conclusions:

• While mitochondrial genetics may contribute to POAG susceptibility in African-Americans, novel mutations detected in peripheral blood mtDNA are unlikely to be the primary cause.
• The study found a significantly lower incidence of novel mtDNA variations in POAG cases than previously suggested.
• These findings challenge the hypothesis that a high rate of novel mtDNA mutations drives mitochondrial respiratory dysfunction in African-American POAG patients.