RDA coupled with deep sequencing detects somatic SVA-retrotranspositions and mosaicism in the human brain

Area of Science:

• Neurogenetics
• Molecular Evolution
• Genomics

Background:

• Genetic and epigenetic alterations in the developing human brain contribute to somatic mosaicism and neurogenetic disorders.
• Mobile transposable elements (TEs), like SINE-VNTR-Alu (SVA), are mobilized by LINE-1 activity during brain development, causing de novo insertions.
• TE presence/absence offers informative clade markers for neural cell lineage and nervous system evolution.

Purpose of the Study:

• To investigate the occurrence and patterns of de novo SVA insertions in the somatic human brain.
• To determine if SVA mobility in the germline is reflected in somatic brain cells.
• To utilize SVA insertion sites as markers to reconstruct brain region evolutionary relationships.

Main Methods:

• Representational Difference Analysis (RDA) coupled with deep sequencing was employed to compare SVA insertion patterns across different human brain regions.
• SVA insertion positions were analyzed as presence/absence markers.
• Maximum parsimony phylogeny was constructed based on SVA insertion data.

Main Results:

• Somatic de novo SVA integrations were detected in all analyzed human brain regions.
• The majority of de novo insertions were unique to specific brain regions, particularly telencephalon and metencephalon lineages.
• SVA insertions showed preferences for GC-rich and TE-rich regions, often near genes involved in neural-specific pathways.

Conclusions:

• De novo SVA insertions occur in both germline and somatic brain cells, targeting similar genomic regions.
• These insertions contribute to neural cell variability and can serve as valuable markers for tracing cell lineages and brain evolution.
• The findings suggest conserved retrotransposition mechanisms operate in both the germline and soma.