Your Roommate’s Genes May Be Changing Your Health

Our genes are among the most intimate little bits of information that exist, passed down from our parents, and determining the unique traits that make us ourselves.

But what if our social partners’ genes, too, exert some sort of influence on who we are? That’s the startling implication of a new study in mice, published in PLOS Genetics. Scientists in the UK found that many health traits in lab mice—such as anxiety, body weight, the immune system, and the rate at which the body heals from injury—all seem to be, in part, affected by the genes of other mice who share their cage.

It’s well-known that peer pressure can influence our health, through bad habits like smoking. But how genes in one individual may affect another is far less understood. While there’s evidence from other animal studies that a mother’s genes influence the wellbeing of her babies, the idea that social partner’s genes could affect not just one’s behavior but also their body may seem bewildering. How could this even work?

An attentive cage mate could have promoted the healing by licking the wound

It’s far from clear. The study shows that partners’ genes work indirectly through what’s known as social genetic effects (SGEs), whereby the genes in one individual impact the health of another.

“It was eye opening to see that social genetic effects can affect a wide variety of health traits. It’s easy to see why some behavioral traits, like anxiety for example, are affected. But we also found that SGE affect immune function and the rate of wound healing. This was quite surprising,” said Amelie Baud, a postdoctoral researcher at the European Bioinformatics Institute (EBI) in Cambridge UK, who did the bulk of the work.

Baud and her colleagues measured how more than 100 health traits change in response to the cage mates’ genetic makeup. By combining data from some 2,500 mice, she was able to calculate how much of the difference in mouse health can be explained not by their own genes, but by those of their cage mates.

For anxiety, this was around 12 percent, whereas the rate of skin wound closure came up to 18 percent. And for immune response, measured by the body’s readiness to fight infections, the partners’ genes carried even more weight than those in the measured animals.

Read More: Is Your Open Office Making You Sick?

The effects on the immune system and wound healing in particular are puzzling. It’s hard to see how this can be orchestrated by someone else’s genes. There are several possible explanations, according to Oliver Stegle, a geneticist at the EBI and the head of the team that carried out the work.

One way, he said, is through direct contact between mice—an attentive cage mate could have promoted the healing by licking the wound, whereas a scrappy partner would have made it worse. Or, the effect might have been indirect, triggered by stress, which is known to impede the body’s immune defense and healing processes.

Although such effects have not yet been explored in humans, it’s easy to imagine how a stressful social life might take its toll on health.

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Scientists Are Furious Over Canada’s Bizarre Ban on Importing Zebrafish

As far as pets go, the zebrafish has more than earned its stripes. An aquarium staple, it is also used by scientists around the world, who can watch, second by second, what happens inside its see-through body to shed light on why some people are more prone to tuberculosis, for example, or end up with a painfully curved spine.

Canadian researchers are contending with severe restrictions on zebrafish import to this country, and they say it’s hurting their research. As a result, some have had to put certain studies on hold, including those involving Alzheimer’s, blindness, heart disease and arthritis. “The import ban has no solid scientific basis, and is not emulated by all other countries who have zebrafish importation. The whole thing just does not make sense,” said Vincent Tropepe, Chair of Cell and Systems Biology at the University of Toronto.

This zebrafish embryo has its nerve cells labeled in technicolor. Image: Albert Pan and Alex Schier

The Canadian Food Inspection Agency (CFIA) imposed the embargo in 2013 in a bid to protect its waters from disease outbreak, on the grounds that zebrafish could be susceptible to a carp virus and might cause it to spread.

Although the virus poses no threat to people, it causes nasty internal bleeding in fish, killing about a third of them during outbreaks.

The decision has left many in the research community scratching their heads: there’s no evidence that zebrafish can spread the virus. The virus is also widespread globally, including in Canada, yet this is one of the few countries with such an embargo in place. (The others include Australia, Israel, South Korea, Malaysia and Bermuda.)

As a result, Canadian researchers have trouble accessing some cutting-edge zebrafish strains. In the last two decades, scientists have created more than 20,000 genetically modified zebrafish strains—lacking certain genes, or whose cells and organs light up with fluorescent proteins—to be used as research tools. These are kept in central stocks in Germany and the US and are openly shared across the world. While many strains already exist in Canada, there’s a limit to how many fish tanks a lab can keep due to space constraints, and new strains are imported as needed, although that’s proving to be difficult under the existing embargo.

This zebrafish embryo with a glowing heart is helping scientists understand why some people are born with heart damage Video: Ian Scott/YouTube

In his lab at the University of Alberta, Ted Allison uses zebrafish to study mad cow disease, a condition caused by sticky proteins that gunk up, and eventually kill, brain cells. When a colleague in the US created a fish whose brains glow green when hit by the disease, Allison wanted to use the strain to search for drugs that can switch off the green in the brain and make it healthy again.

Before the embargo, Allison would have just asked the colleague to mail the fish to Canada. Or, if that was not possible, he would have ordered the strain from a central stock. But now, instead of buying an off-the-shelf ready fish for a few hundred dollars, the Canadian scientists have to make it from scratch, which takes at least a year and could tally up to $20,000.

Allison had a researcher in his lab recreate the mad cow zebrafish, calling the year and half it took “wasted time”. The resentment is echoed by other researchers, who also had to divert their taxpayer-funded grants to recreate the existing strains so they can actually do the science they got funded for in the first place. They’re worried they’ll be left eating the dust as their international competitors take advantage of all strains available outside Canada.

Read More: Scientists Are Creating Mutant Fish With Curvy Spines to Study Scoliosis

The CFIA said in an e-mail that import restrictions were a result of zebrafish being listed as susceptible to virus by the World Organization for Animal Health (OIE), which sets global standards for animal health and trade for its 180 state members, including Canada. But the OIE’s decision did not call for an embargo, which is warranted only when the fish are a natural host for a virus and can spread it in the waters. Neither is true for zebrafish. In fact, the only way to get the virus into a zebrafish is to inject it, and even then the fish aren’t contagious.

Besides that, scientists take all kinds of precautions to make sure that viruses aren’t being swapped among lab animals, which could wipe out their research, sending years of work and lots of funding dollars down the drain.

“We are not working with these fish casually and there’s already in place a very structured containment program for these animals. We’ve been working with them for decades and I am yet to hear about any disease outbreaks,” said Daniel Dragon, a biosafety officer at the University of Alberta.

To get around the embargo, research facilities are required to boost the existing quarantine measures for new fish arrivals—an onerous task that only the largest facilities can meet, leaving smaller labs no choice but to continue to recreate the strains.

The CFIA is aware of the researchers’ concerns, but shows no sign of loosening restrictions.

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Our Hearts Start Beating Before They’re Fully Formed

During an average lifetime, a human heart beats two-and-a-half billion times. But how does it start, and what came first—the heart or the beating? Scientists think they put their finger on the first heartbeat, which occurs in the embryo long before there’s anything that even remotely resembles the heart, as reported in the journal eLIFE. The study could have important implications for the field of regenerative medicine, and help scientists figure out how to build new hearts from scratch in the lab.

The heart is the first organ to form so that it can send oxygen and nutrients across a growing embryo. In the mouse, one week after fertilization, the heart starts off as a flat field of heart progenitor cells—immature cells that came from stem cells and which are gradually becoming real heart cells. Within the next 24 hours, the heart progenitors will come together to form a tube, which loops back onto itself to finally make a recognizable heart.

The beginnings of the heartbeat. Video: Tyser, Miranda et al./eLife. GIF by Navi Lamba

Previously it was thought that the beating started just as the heart tube was coming together. But now, scientists from the United Kingdom have pushed back the occurrence of the first heartbeat in mice by 12 hours, to a time when heart progenitors are scattered over a wide area.

Because mice develop faster than we do, this corresponds to roughly day 20 in human development in utero. By this time, the undeveloped foetus will have gone from being a single cell to a worm-like creature. It does not yet have arms or legs—not even a head, although the brain has started to form. But amazingly, it does have a heartbeat.

Stripped down to bare chemistry, heartbeats are bursts of calcium inside the heart muscle cells. As calcium levels rise and fall, they make the cells contract and relax, enabling the heart to work as a pump and move blood around the body.

Within a couple of hours, the calcium pulses are synchronized and cells have matured enough to be able to contract and beat visibly. Video: Tyser, Miranda et al./eLife. GIF by Navi Lamba

To find the first heartbeat, the researchers made movies of mouse embryos as they developed in a dish, zooming in on the heart progenitor cells. By every measure, these cells are much too young to be called heart cells and lack the key machinery that turns calcium pulses into contractile force. Yet, surprisingly, when the researchers injected embryos with calcium that fluoresces, they could see flickering calcium waves—the beginnings of the heartbeat.

“We were surprised to find that calcium activity preceded the assembly of the machinery that does the contraction. You could imagine that the contraction machinery would have been in place first, waiting for the calcium signal to arrive, but in fact it was the other way around,” said Shankar Srinivas, a professor of developmental biology at the University of Oxford, who co-led the study.

Read More: The Design Bias of Heart Failure

These early calcium waves aren’t just for show. They seem to be important for normal development, because blocking them by drugs messed up the cells’ ability to become mature heart cells and form the heart.

It adds to an emerging theme in embryo research, where immature cells “grow up” by relying on molecular pathways previously thought to operate only in older cells, said Ian Scott, a senior scientist who studies heart development at the Hospital for Sick Children in Toronto. He was not involved in this study.

The calcium waves start off haphazardly in cells far apart, like lost fireflies. But then quickly—within a couple of hours—they come together to pulse in synchrony at a point when the beating becomes visible for the first time. Researchers want to find out how this switch occurs to be able to make functional heart tissue in the lab and to better understand heart disease.

“One of the major problems in regenerative medicine is how to make heart cells that beat in a coordinated manner. If we can understand how this occurs during development, it might help us engineer heart tissue with better synchrony,” said Srinivas.

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