Approximately half of the gene sequences of human and mouse genomes comes from so-called mobile elements—genes that jump around the genome. Much of this DNA is no longer capable of moving, but is likely “auditioning” perhaps as a regulator of gene function or in homologous recombination, which is a type of genetic recombination where the basic structural units of DNA, nucleotide sequences, are exchanged between two DNA molecules to repair breaks in the DNA strands. Modern mammalian genomes also contain numerous intact movable elements, such as retrotransposon LINE-1, that use RNA intermediates to spread about the genome.
Given the crucial role of the precursor cells to egg and sperm, called germ cells, to continue a species, their genomes represent a particularly attractive target for mobile elements. One lab looks at the uncontrolled activity of retrotransposons, which causes new mutations and even kill germ cells, which is countered by specialized defensive mechanisms regulating LINE-1 elements through the analysis of function of Maelstrom, a protein found in many species, which is implicated in silencing jumping genes in flies and mice by means of specialized small RNAs known as Piwi-interacting RNAs (or piRNAs). The group is trying to uncover and understand how LINE-1 elements impact germ cells during normal development.