Identification of human-specific AluS elements through comparative genomics.

Area of Science:

• Genomics
• Molecular Biology
• Evolutionary Biology

Background:

• Mobile genetic elements constitute approximately 45% of the human genome.
• Alu elements, a major type of mobile element, comprise 10% of the human genome (>1.1 million copies) and are implicated in genetic diseases and rearrangements.
• The AluS subfamily, an ancient and abundant group, is particularly significant in primate genomes.

Purpose of the Study:

• To computationally and experimentally validate previously identified human-specific AluS insertions.
• To investigate alternative Alu insertion mechanisms and their associated genomic alterations.
• To explore the relationship between DNA methylation and the fixation of AluS elements in the human genome.

Main Methods:

• In silico analysis and manual inspection of AluS loci across primate genomes.
• Polymerase chain reaction (PCR) amplification and DNA sequencing for validation.
• Bisulfite sequencing to assess DNA methylation levels of AluS elements.

Main Results:

• 23 human-specific AluS elements were computationally and experimentally verified, with two near-parallel insertions identified as computational false negatives.
• Three alternative Alu insertion events involving filler DNA and/or Alu retrotransposition-mediated deletion were reported.
• Fixed AluS elements exhibited higher DNA methylation levels compared to polymorphic elements.

Conclusions:

• The study successfully validated a significant number of human-specific AluS insertions.
• Alu retrotransposition can involve complex mechanisms including filler DNA and deletions.
• DNA methylation appears to correlate with the fixation of AluS elements in the human genome, suggesting a regulatory role.