The transmission of human mitochondrial DNA in four-generation pedigrees

Area of Science:

• Genetics
• Molecular Biology
• Evolutionary Biology

Background:

• Pathogenic mitochondrial DNA (mtDNA) variants often exist as heteroplasmies.
• Understanding mtDNA transmission is key for predicting mitochondrial disease risk.
• Previous studies lacked multigenerational data, limiting insights into transmission randomness.

Purpose of the Study:

• To analyze the transmission patterns of mtDNA heteroplasmies across four generations.
• To investigate the randomness and potential selection pressures on mtDNA variant frequencies during inheritance.

Main Methods:

• Analysis of mtDNA heteroplasmy transmission in 16 four-generation families.
• Quantification of variant frequency changes across generations.
• Estimation of effective bottleneck size during mtDNA transmission.

Main Results:

• 57.8% of variants from the great grandmother were transmitted to the fourth generation.
• Transmission direction and magnitude of variant frequencies were largely random.
• One nonsynonymous variant (m.15773G>A) showed consistent frequency increase in one family, suggesting a potential fitness advantage.
• Effective bottleneck size was estimated to be 21-71.

Conclusions:

• Multigeneration data reveal complex mtDNA heteroplasmy transmission dynamics.
• Most mtDNA variants appear neutral or mildly deleterious, lacking strong selection.
• Specific variants may confer a selective advantage, influencing their transmission.
• This study enhances understanding of mtDNA mutation frequency dynamics in inheritance.