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Inheriting microbes

The DNA of bacteria that live in the body can pass a trait to offspring in a way similar to the parents’ own DNA, a new mouse study suggests. According to the study’s authors, the discovery means scientists need to consider a significant new factor – microbial DNA– in their efforts to understand how genes influence illness and health.

WASHINGTON UNIVERSITY RESEARCHERS HAVE DISCOVERED THAT GENES AREN’T THE ONLY THINGS THAT CAN PASS ALONG TRAITS TO OFFSPRING. IN STUDIES OF MICE, THEY’VE LEARNED THAT THE BACTERIA IN THE GUT ALSO IS CAPABLE OF CARRYING TRAITS FROM MOTHER TO BABY. JIM DRYDEN REPORTS…

IT’S BECOME CLEAR IN RECENT YEARS THAT MUCH OF WHAT MAKES US “US” ISN’T HUMAN TISSUE. MICROBES THAT COLONIZE OUR BODIES ACTUALLY PERFORM SEVERAL FUNCTIONS THAT OUR OWN CELLS DON’T. AND, IT TURNS OUT THAT, AT LEAST IN MICE, THE BACTERIA FROM THE GUT ALSO HAS THE CAPACITY TO PASS TRAITS FROM MOTHERS TO THEIR OFFSPRING. WASHINGTON UNIVERSITY RESEARCHERS SKIP VIRGIN AND THADDEUS STAPPENBECK WERE STUDYING MICE, IN EXPERIMENTS AIMED AT BETTER UNDERSTAND INFLAMMATORY BOWEL DISEASE, WHEN STAPPENBECK SAYS, THEY NOTICED THAT A LOT OF THE MICE HAD VARYING LEVELS OF A SUBSTANCE IN THE GUT CALLED IMMUNOGLOBULIN A, OR IGA FOR SHORT.

(act) :26 o/c totally wrong

So the first experiment we did was we took mice that

were IGA-high and IGA-low, and we just mixed them in a

cage and waited a few weeks. So I thought, from the

literature, I thought because there are supposed to be

microbes in the gut that induce IGA, that the result of

that experiment would be really simple. You would take

the high and put it in with the low, and then everyone

would have the IGA-inducing bug, and everyone would be

high. That was totally wrong.

INSTEAD, ALL OF THE MICE STARTED MAKING LOW LEVELS OF IGA. IT TURNED OUT THAT A PARTICULAR TYPE OF BACTERIA IN THE GUT CALLED SUTTERELLA TRIGGERED THE CHANGE. AND WHEN MICE LIVED TOGETER IN THE SAME CAGE, THOSE WO HAD SUTTERELLA AND MADE LOW LEVELS OF IGA PASSED THAT BACTERIA ALONG TO THEIR CAGE-MATES WHO ALSO STOPPED MAKING HIGH LEVELS OF IGA AND BEGAN MAKING LESS OF THAT SUBSTANCE. BUT, IN OTHER EXPERIMENTS, STAPPENBECK SAYS, THEY FOUND THAT THE SAME TRAIT COULD BE PASSED IN THE MICE FROM MOTHERS TO THEIR PUPS.

(act) :18 o/c of this

So the microbe could be passed horizontally, and then

we also checked our colony, and we realized that IGA-low

mice gave birth to IGA-low mice; and IGA-high mice gave

birth to IGA-high mice. So it was not only horizontally

transmittable but also vertically transmittable. So this

is the inheritance part of this.

WHAT THAT MEANS, STAPPENBECK SAYS, IS THAT IT ISN’T ONLY GENES THAT CAN PASS TRAITS FROM MOTHER TO BABY. GUT BACTERIA ARE CAPABLE OF DOING THE SAME THING.

(act) :09 o/c to pups

It’s the heritability of microbes that’s really critical.

The endpoint is, basically, showing that you’ve, you’ve,

passed the microbes from mom to pups.

STAPPENBECK AND VIRGIN SAY THEIR DISCOVERY THAT THE GUT IS INFLUENCED NOT ONLY BY INHERITED GENES BUT ALSO BY INHERITED MICROBES SHOULD HELP THEM BETTER UNDERSTAND THE CAUSES OF INFLAMMATORY BOWEL DISEASE. IT ALSO MAY PROVIDE A TARGET FOR TREATMENTS THAT WOULD USE MICROBES TO MODIFY TRAITS RATHER THAN MANIPULATE GENES TO DO THAT. FOR NOW, HE SAYS, IT MEANS RESEARCHERS NEED TO BE REALLY CAREFUL WHEN STUDYING MICE.

(act) :17 o/c the microbiome

This means you have to do things like littermate controls,

or you have to pay attention to the microbiome. You can’t

have a line of knockout mice and then a line of control

mice under separate breeding, not connected to each other

because you can get fooled by differences in the microbiome.

STAPPENBECK AND VIRGIN REPORT THEIR FINDINGS IN THE JOURNAL NATURE. I’M JIM DRYDEN…

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