A structure-selective endonuclease drives uniparental mitochondrial DNA inheritance

Area of Science:

• Genetics
• Molecular Biology
• Developmental Biology

Background:

• Maternal inheritance of mitochondrial DNA (mtDNA) is common in eukaryotes.
• Mechanisms preventing paternal mtDNA inheritance in sperm are not fully understood.
• Active elimination of paternal mtDNA occurs during spermatogenesis in organisms like Drosophila and humans.

Purpose of the Study:

• To identify the molecular factors responsible for paternal mtDNA elimination in sperm.
• To elucidate the mechanism by which paternal mtDNA is degraded during spermatogenesis.

Main Methods:

• Identification and characterization of a novel testis-specific endonuclease, named Hotaru.
• Analysis of Hotaru expression and localization within spermatids.
• Genetic studies using hotaru mutants to assess the role in paternal mtDNA elimination.
• Biochemical assays to determine Hotaru's DNA cleavage specificity.

Main Results:

• Hotaru, a GIY-YIG endonuclease, is essential for paternal mtDNA elimination.
• Hotaru is expressed in elongated spermatids and localizes to the mitochondrial matrix.
• hotaru mutants exhibit retained paternal mtDNA in mature sperm.
• Hotaru specifically cleaves cruciform DNA structures in the mtDNA control region.

Conclusions:

• Hotaru is a key nuclease enforcing paternal mitochondrial genome elimination in the male germline.
• The structural feature of mtDNA (cruciform DNA) acts as a determinant for its destruction.
• This structure-specific recognition mechanism provides robustness against mtDNA mutations.