LINE-1 elements: analysis by fluorescence in-situ hybridization and nucleotide sequences

Area of Science:

• Genomics
• Evolutionary Biology
• Molecular Biology

Background:

• Long interspersed nuclear element-1 (LINE-1) are major components of mammalian genomes with dynamic evolutionary histories.
• LINE-1 distribution can be studied at chromosomal and sequence levels.

Purpose of the Study:

• To investigate the genomic distribution and evolutionary relationships of LINE-1 elements across diverse mammalian species.
• To determine if LINE-1 accumulation in AT-rich regions, observed in humans and mice, is a universal mammalian phenomenon.

Main Methods:

• Designed conserved LINE-1 primers to amplify ORF2 regions from eutherian mammals.
• Utilized PCR products as fluorescence in-situ hybridization (FISH) probes for genomic mapping.
• Performed phylogenetic analyses using sequenced amplicons and public L1 databases.

Main Results:

• LINE-1 distribution patterns vary significantly across mammalian orders, differing from the AT-rich accumulation seen in humans and mice.
• The "banding" pattern of LINE-1 in humans and mice appears specific to the Euarchontoglires clade.
• Phylogenetic analyses of LINE-1 sequences generally reflect accepted eutherian evolutionary relationships.

Conclusions:

• LINE-1 distribution is not universally concentrated in AT-rich regions; observed patterns in humans/mice are clade-specific.
• LINE-1 elements provide insights into mammalian genome architecture and evolutionary history.
• Active LINE-1 copies are often lineage-specific and tend to become extinct rapidly.