Evidence of horizontal DNA transfer `uncovered`

Washington: Scientists claim to have found for the first time solid evidence of horizontal DNA transfer - movement of genetic material between parasitic invertebrates and some of their vertebrate hosts.

In their research, a team at Texas University, led by C’dric Feschotte, unearthed the evidence of horizontal transfer of transposon from a South American blood-sucking bug
and a pond snail to their hosts, `Nature` journal reported.

A transposon is a segment of DNA that can replicate itself and move around to different positions within the genome. Transposons can cause mutations, change the amount of DNA in the cell and dramatically influence the structure and function of the genomes where they reside.

"Since these bugs frequently feed on humans, it is conceivable that bugs and humans may have exchanged DNA through the mechanism we uncovered. Detecting recent transfers to humans would require examining people that have been exposed to the bugs for thousands of years, such as native South American populations," Feschotte said.

Data on the insect and the snail provide strong evidence for the previously hypothesised role of host-parasite interactions in facilitating horizontal transfer of genetic material.

The infected blood-sucking triatomine, causes Chagas disease by passing trypanosomes (parasitic protozoa) to host. The scientists found the bug shared transposon DNA with some hosts, namely the opossum and the squirrel monkey.

The transposons found in the insect are 98 percent identical to those of its mammal hosts.

They also identified members of what Feschotte calls space invader transposons in the genome of Lymnaea stagnalis, a pond snail that acts as an intermediate host for trematode
worms, a parasite to a wide range of mammals.

"When you are trying to understand something that occurred over thousands or millions of years ago, it is not possible to set up a laboratory experiment to replicate what happened in nature," Feschotte said.

Instead, the scientists made their discovery using computer programs designed to compare the distribution of mobile genetic elements among the 102 animals for which entire genome sequences are currently available.