Sea lamprey can dramatically remodel its genome

Washington, July 21 (ANI): In a new research, scientists have discovered that the sea lamprey, which emerged from jawless fish first appearing 500 million years ago, dramatically remodels its genome.

The research found that shortly after a fertilized lamprey egg divides into several cells, the growing embryo discards millions of units of its DNA.

This is believed to be the first recorded observation of a vertebrate - an animal with a spinal column - extensively reorganizing its genome as a normal part of development.

A few invertebrate species, like some roundworms, have been shown to undergo extensive genome remodeling.

However, stability was thought to be vital in vertebrates' genomes to assure their highly precise, normal functioning.

Only slight modifications to allow for immune response were believed to occur in the vertebrate genome, not broad-scale rearrangements.

Jeramiah Smith, a postdoctoral fellow in genome sciences at the University of Washington (UW), Chris Amemiya, who is also a UW affiliate professor of iology, and their research team inadvertently discovered the dynamic transformations in the sea lamprey genome while studying the genetic origins of its immune system.

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.

"The remodeling begins at the point when the embryo turns on its own genes and no longer relies on its mom's store of mRNA," said Smith.

The restructuring doesn't occur all at once, but continues for a long while during embryonic development. It took at lot of work for the scientists to see what was lost and when.

They learned, among other findings, that the remodeled genome had fewer repeats and specific gene-encoding sequences.

Deletions along the strands of DNA are also thought to move certain regulatory switches in the genome closer to previously distant segments.

According to Smith, the extra genetic material might play a role in the proliferation of precursor cells for sperm and eggs, and in early embryonic development.

The genetic material might then be discarded either when it is no longer needed or to prevent abnormal growth. (ANI)