Tuesday, February 17, 2015

Bacterial DNA can be passed to offspring in mother's body

Although it is well known that genetic traits are passed from
parent to child through DNA, a new study published in Nature finds that traits can also be passed to the child via the DNA of bacteria in the mothers' body.

"We have kept bacteria on one side of a line separating the
factors that shape our development - the environmental side of that line, not the genetic side," says co-senior author Dr. Herbert W. Virgin IV, the Edward Mallinckrodt professor of Pathology and head of the Department of Pathology and Immunology at Washington University School of Medicine in
St. Louis (WUSTL).

"But our results show bacteria stepping over the line," Dr.
Virgin continues. "This suggests we may need to substantially
expand our thinking about their contributions, and perhaps the
contributions of other micro-organisms, to genetics and

"Commensal bacteria" are organisms that live within our bodies but do not cause disease. However, these bacteria are known to influence weight, behavior and other traits.

Scientists had previously believed the genetic traits associated with commensal bacteria to be acquired during a person's lifetime rather than inherited.

However, the new study shows for the first time that bacterial DNA can pass between a mother and her offspring, and that the transference of this DNA
influences traits including immunity and inflammation.

In the new study, the researchers found that mice with certain bacteria inherited from their parents were more susceptible to a gut injury caused by chemical exposure.

Mice carrying other inherited bacteria, however, were less susceptible to this condition.
The researchers believe that the findings of the study - as well
as expanding knowledge on how DNA is transmitted - also have important practical implications for science.

Findings explain 'glitch' sometimes encountered in mouse studies

Across several fields of research, scientists have reported an occasional glitch when conducting experiments using genetically engineered mice, where new or altered genetic traits can suddenly appear in the mice in a way that cannot be easily explained.

Scientists believed that microbial infection was the most likely culprit, as these traits appeared to spread between mouse
habitats. However, what confused scientists is that the traits
were also consistently passed from mother to offspring,
implying a genetic cause.

The findings of the new study suggest an explanation for this
by showing how traits in mice can be affected by bacteria that
is spread normally among a cohabiting population, but also
how those bacteria-influenced traits are passed from mothers to offspring.

Dr. Thaddeus Stappenbeck, a professor of pathology and
immunology at WUSTL, says of the study: Dr. Stappenbeck adds that a workaround for the problem of
altered or new traits in genetically modified mice could be to house experimental and control mice in the same colony, which would ensure that inherited microbes are present in both groups.

Dr. Virgin says he expects a much more complicated picture of
heredity to emerge following the findings of this study that will
provide more insights of how human, bacterial and viral genes
influence human health.