Transposon insertion profiling by sequencing (TIPseq) identifies novel LINE-1 insertions in human sperm

Area of Science:

• Genomics
• Human Genetics
• Molecular Biology

Background:

• Long Interspersed Nuclear Element-1 (LINE-1 or L1) constitutes 17% of the human genome.
• Retrotransposons can disrupt gene integrity and expression by altering genomic regulatory regions.
• Germline silencing of retrotransposons via cytosine methylation is lifted during germ cell and early embryo development.

Purpose of the Study:

• To investigate de novo retrotransposition in human sperm.
• To utilize single cell transposon insertion profiling by sequencing (scTIPseq) to map these insertions.
• To explore the potential link between sperm de novo genetic variation and offspring disorders.

Main Methods:

• A cross-sectional case-control study involving sperm samples from 10 men (ages 32-55).
• Application of scTIPseq to identify novel LINE-1 insertions in individual sperm.
• Bioinformatic analysis using TIPseqHunter to compare sperm LINE-1 insertions with the euL1db database.

Main Results:

• scTIPseq detected 17 novel LINE-1 insertions in human sperm.
• These new insertions were predominantly located in intergenic or intronic regions.
• No significant correlation was observed between paternal age and the number or location of novel insertions.

Conclusions:

• This study provides the first evidence of novel LINE-1 insertions in human sperm.
• It demonstrates the feasibility and effectiveness of the scTIPseq method.
• Identifies novel contributors to genetic diversity within the human germline.