Ancient genomic architecture for mammalian olfactory receptor clusters

Area of Science:

• Genomics
• Evolutionary Biology
• Olfactory Receptor Research

Background:

• Mammalian olfactory receptor (OR) genes are organized in numerous genomic clusters.
• Comparative genomics of five mammals aids in reconstructing the ancestral olfactory subgenome.

Purpose of the Study:

• To develop a general tool for identifying conserved genomic gene clusters across multiple species.
• To reconstruct the ancestral mammalian olfactory subgenome by analyzing olfactory receptor gene clusters.

Main Methods:

• Developed a genome-wide tool to define conserved gene clusters using syntenic orthologs.
• Applied a graph theory algorithm to identify conserved olfactory receptor gene clusters (CLICs) in five mammals.
• Analyzed inter-species differences in CLICs to understand genomic rearrangements and evolutionary dynamics.

Main Results:

• Over 90% of olfactory receptor genes in five mammals were found within 48 conserved multi-species CLICs.
• CLICs demonstrate conserved gene order and composition across mammalian species.
• Identified species-specific differences, including a human-specific deletion in CLIC #1 potentially linked to isovaleric acid detection.

Conclusions:

• The majority of mammalian OR clusters originated from a common ancestor before the marsupial-placental split.
• Only two CLICs incorporated chicken OR genes, suggesting most OR clusters emerged after avian-mammalian divergence.