Sea Lamprey’s Genome Mystery

Researchers have discovered that the sea lamprey, which emerged from jawless fish first appearing 500 million years ago, dramatically remodels its genome. Shortly after a fertilized lamprey egg divides into several cells, the growing embryo discards millions of units of its DNA. The researchers were trying to deduce how the sea lamprey employs a copy-and-paste mechanism to generate diverse receptors for detecting a variety of pathogens.

The researchers were surprised to notice a difference between the genome structure in the germline – the cells that become eggs and the sperm that fertilize them – and the genome structure in the resulting embryonic cells. The DNA in the early embryonic cells had myriad breaks that resembled those in dying cells. But the cells weren’t dying. The embryonic cells had considerably fewer repeat DNA sequences than did the sperm cells and their precursors.

Learning how sea lamprey DNA rearrangements are regulated during development might provide information on what stabilizes or changes the genome, as well as the role of restructuring in helping form different types of body cells, like fin, muscle, or liver cells.

Icon image credit: University of Washington