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Related Concept Videos

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Sequencing of the human genome has opened up several best-kept secrets of the genome. Scientists have identified thousands of genome variations that exist within a population. These variations can be a single nucleotide or a larger chromosomal variation.
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Among all the organelles in an animal cell, only mitochondria have their own independent genomes. Animal mitochondrial DNA is a double-stranded, closed-circular molecule with around 20,000 base pairs. Mitochondrial DNA is unique in that one of its two strands, the heavy, or H, -strand is guanine rich, whereas the complementary strand is cytosine rich and called the light, or L, -strand. Compared to nuclear DNA, mitochondrial DNA has a very low percentage of non-coding regions and is marked by...
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A single nucleotide polymorphism or SNP is a single nucleotide variation at a specific genomic position in a large population. It is the most prevalent type of sequence variation found in the human genome. Point mutations that occur in more than 1% of the population qualify as SNPs. These are present once every 1000 nucleotides on an average in the human genome. Replacement of a purine with another purine (A/G) or a pyrimidine with another pyrimidine (C/T) is known as a transition. In contrast,...
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Related Experiment Video

Updated: May 17, 2025

Measuring Single-Cell Mitochondrial DNA Copy Number and Heteroplasmy Using Digital Droplet Polymerase Chain Reaction
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rDNA Copy Number Variation and Methylation in Human and Mouse Sperm.

Ramya Potabattula1, Marcus Dittrich1,2, Thomas Hahn3

  • 1Institute of Human Genetics, Julius Maximilians University, 97074 Würzburg, Germany.

International Journal of Molecular Sciences
|May 14, 2025
PubMed
Summary

Paternal age impacts rDNA methylation in sperm, with more hypomethylation in mice than humans. This age-related epigenetic change is conserved but differs between species, potentially affecting embryonic development.

Keywords:
absolute rDNA copy numberactive rDNA copy numberaging human and mouse germlinedeep bisulfite sequencingdroplet digital PCRsperm rDNA methylation

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Area of Science:

  • Reproductive Biology
  • Epigenetics
  • Genomics

Background:

  • Ribosomal DNA (rDNA) copy number (CN) and methylation are crucial for gene regulation.
  • Paternal age is increasingly recognized as a factor influencing sperm epigenetics and offspring health.
  • Understanding species-specific differences in germline epigenetics is vital for reproductive science.

Purpose of the Study:

  • To investigate the absolute and active rDNA copy number (CN) in human and mouse sperm.
  • To examine the effect of paternal age on rDNA methylation patterns in both species.
  • To compare rDNA methylation dynamics and paternal age effects between humans and mice.

Main Methods:

  • Droplet digital PCR (ddPCR) for absolute rDNA copy number quantification.
  • Deep bisulfite sequencing for analyzing rDNA methylation status.
  • Comparative analysis of human and mouse sperm samples across different paternal ages.

Main Results:

  • Absolute rDNA CN varied significantly, with higher numbers in human sperm compared to mouse sperm.
  • Methylation of rDNA regulatory regions increased with paternal age and absolute CN in both species.
  • Mouse sperm exhibited more pronounced rDNA hypomethylation, particularly in the promoter regions, compared to human sperm.
  • Despite higher CN in humans, the number of hypomethylated promoter copies was comparable, but methylation errors differed.
  • Paternal age effects on rDNA methylation were conserved but showed species-specific patterns, with a decrease in hypomethylated copies in humans and unmethylated copies in mice.

Conclusions:

  • Germline rDNA methylation dynamics show significant species-specific differences between humans and mice, possibly linked to reproductive strategies and embryonic development timing.
  • Complete demethylation of sperm rDNA promoters in mice may facilitate early embryonic genome activation.
  • The conserved yet distinct paternal age effect on rDNA methylation highlights the complex interplay between aging, epigenetics, and reproduction across species.