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Complex evolution of 7E olfactory receptor genes in segmental duplications
1Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
Genome Research
|May 3, 2003
Summary
Large segmental duplications (SDs) drive genome complexity. A specific subset, the 7E SDs, containing numerous olfactory receptor (OR)-like genes, show complex duplication patterns and potential functional roles despite appearing as pseudogenes.
Area of Science:
- Genomics
- Human Genetics
- Molecular Biology
Background:
- Large segmental duplications (SDs) significantly contribute to human genome size, complexity, and diversity.
- SDs are implicated in chromosomal rearrangements linked to disease and speciation.
- Olfactory receptor (OR) genes are known to be highly duplicated and variable.
Purpose of the Study:
- To identify and characterize a specific subfamily of olfactory receptor (OR)-like genes, termed 7Es, within large segmental duplications (SDs).
- To investigate the genomic distribution, duplication history, and evolutionary mechanisms of these 7E-containing SDs (7E SDs).
- To explore the functional potential and evolutionary pressures acting on 7E genes, particularly those appearing as pseudogenes.
Main Methods:
- Bioinformatic analysis of human genome sequences to identify SDs and the 7E gene subfamily.
- Comparative genomics to assess gene pseudogenization and evolutionary conservation.
- Analysis of duplication events (intra- and interchromosomal) and gene conversion signatures.
Main Results:
- Identified 7E SDs comprising an 88-member OR-like gene subfamily, with over 92% appearing as pseudogenes.
- Documented extensive duplication of 7E SDs across at least 35 genomic regions through complex intra- and interchromosomal events.
- Observed evidence of gene conversion and sequence exchange between 7E SDs, suggesting mechanisms facilitating ectopic interactions.
- Found that 7E SDs are not restricted to pericentromeric or subtelomeric regions, unlike many other human SDs.
- Detected signatures of purifying selection in some 7E genes and confirmed expression of at least one 7E gene.
Conclusions:
- The complex duplication history and structure of 7E SDs necessitate an updated model for large-scale DNA duplication.
- Despite high pseudogenization rates, some 7E genes show evidence of evolutionary constraint and functional activity, indicating potential roles.
- The study highlights the dynamic nature of the human genome and the role of SDs in shaping genetic diversity and potentially disease.