Sebastian Seung could have hired an army of undergraduates to do crucial legwork in his neuroscience lab at MIT. Even with the help of powerful computers that would have taken years. Instead, he and his lab turned it into a game, called it Eyewire, and 10,000 people played it on the first day. Many are still at it. These players hold all conceivable occupations, but in their free time they are neuroscientists: a prime example of scientists partnering with the public in citizen science projects. Collecting or organizing vast amounts of data might take one or two scientists years, but with thousands of people helping, data sets are complete in months or weeks, and discovery accelerates.
The goal of Eyewire is to trace individual neurons in the the tangles of a mouse’s retina. Many people map the same neuron, and results are averaged for better accuracy. Accuracy against the average wins points, though sometimes a player has to be the trailblazer, the first one to map a new neuron, slowly expanding the map. Collectively, the players turn tangles into data, mapping neuron types, connections, and extensions. Seung is hoping to map the retina as a stepping stone to mapping the whole brain, developing a set of connections he thinks may be unique to each person. This connectome, he says, may make each of us who we are. But to map this vast connectome, the pathways of billions neurons in each person’s head, Seung needed help from both a powerful artificial intelligence, the computer game, and thousands of citizen scientists around the world playing it.
What makes you, you? The nature vs. nurture debate has been going on for more than a century, and recent work with honeybees has managed to make it even more complex. Researchers focused not on the nature part, the bees’ DNA, nor on the nurture part, how the bees grew up and lived, but on a fuzzy gray area in between.
All of the worker bees in a hive are sisters, descended from the same queen. All of these bees grow up together sharing the same environment. Worker bees divide into two groups: nurse bees, who take care of the eggs and larvae, and forager bees, who fly around collecting pollen and nectar. Nurses’ and foragers’ missions are different, but the DNA of these sister bees is quite similar and their nurturing seems to have been the same. How do they end up with different purposes?
Enter epigenetics, a relatively new field that studies how the environment affects the expression of genes. Genes were once thought to be instructions written in stone, unchangable directives for the cell. The nurture effects were thought to go on after the instructions were read, a result of environmental factors, i.e. where a toxic chemical causes cancer or someone overcomes a natural stutter. In reality, the genes themselves get buffeted by the winds of chance and circumstance from the outside world. Epigenetics has found “tags” sitting on top of sections of DNA. These tags control whether the cell will “read” a gene or if it will remain silent. The DNA itself is not actually changed, but its accessibility is. The whole set of DNA, called the genome, is overlaid with a pattern of these tags, called the epigenome.
This epigenome develops throughout life, starting with very few tags at birth. Tags are added or removed due to environmental factors such as nutrition, stress, and disease, allowing cells access to some genes and not others. Not only do these tags accumulate throughout one lifetime, some of them can be passed down to offspring. Which means that parents, grandparents, and various distant relatives all gave some of their epigenome to an individual, contributing to how their genes are expressed. They also contributed DNA, too, but unlike DNA, the epigenome is influenced by lifestyle choices. Those grandparents’ actions and experiences, not just their genes, influence who you are.
After finding no difference between the genome and the epigenomes of the queen bee and workers right after birth, Dr. Andrew Feinberg and his colleagues at Johns Hopkins University examined the differences between the two castes of worker bees: nurses and foragers. These workers perform very different roles in the hive. Usually, newly born bees start out as a nurses, and as older foragers die in the risky outdoors, some of them start foraging. Researchers took care to compare the epigenomes of workers that were the same age, each nurse and forager getting the same amount of time to accumulate epigenetic tags.
In their experimental design, the researchers were sneaky. They took advantage of the ability of the workers’ ability to change jobs: switching back to nurse from forager if the need arises. This doesn’t happen very often, but researchers created the need. If we manipulate their hive a bit, and get some of the forager bees to change back to being nurses, they asked, what will their genome look like then?
While the forager bees were out foraging, the researchers moved the hives, so that the bees came back to another hive, empty of bees but not of honeycomb full of larvae that needed tending. With a distinct need for nurse bees, half of the workers went back to their old jobs. Researchers looked to see if foragers and nurses have different epigenomes, and what type of epigenome the foragers-turned-back-to-nurses had.
It turned out that not only did nurses and foragers have distinct epigenomes, but it seems the epigenome changed with the job. When foraging worker bees were steered back to being nurses, their epigenome, and the genes it allowed to be expressed, reverted back to look like it did when it was a young nurse bee. It was like flipping a switch attached to about 100 genes at the same time, turning them on or off if the worker was fulfilling a nurse role or a forager role. These worker bees acted very differently, and the specific epigenome patterns seem to be the key to why.
This is, as the researchers note in very understated tones, “the first evidence in any organism of reversible epigenetic changes associated with behavior.” Does our epigenome change our behavior or does our behavior change our epigenome? No one knows, but this is evidence of the large role epigenetics plays in each individual. And our epigenome is greatly affected by every facet of the environment we live in. So how did you become you? A murky causal soup of your environment, combined with your genes, combined with the gray area of environmentally-affected gene expression. Epigenetics, and bees, have just made the nature-nurture debate much more interesting.
The friendly takeover is complete! We’re all excited to start gold digging for stories in the world of science, and share what we sift out with you. And we would like to introduce ourselves, those doing the taking-over, before we plunge in as new bloggers. We’re an eclectic bunch, but we’re all interested in translating science into compelling stories.
Alex Kasprak comes to us from Brown University, where he recently earned a M.S. in geological sciences. There, he studied marine, environmental, and ecologic change during one of the largest biotic catastrophes known to the fossil record – the end-Triassic mass extinction. His favorite geologic age is the Hettangian, his favorite animal is the mouse lemur, and his favorite element is sulfur.
Jean Mendoza graduated from Brown University with a degree in English and biology, passions which she combined into science writing at Johns Hopkins. Her interests span from the intersection of science and superstition to medicine and astrophysics. She draws inspiration from Hemingway, Fitzgerald, Joan Didion, Jenny Boully, and Annie Dillard.
Gabe Popkin has come most recently from Madison, WI, and before that from the Washington, DC area, where he worked full-time for the American Physical Society for several years. Gabe has a physics degree from Wesleyan University, and over five years of professional science writing, editing, and communication experience. He loves writing about physics, ecology, and everything in between–with a particular interest in the interactions between humans, our environment, and the rest of life on earth.
Kelsey Calhoun spent last year as a neuroscientist playing with rats, and is here to play with words because rats really can’t keep a discussion going when it comes to the physics of harpsichords, or the chemistry of chemotherapy. She’s interested in almost every field of science, but particularly neuroscience, genetics, ecology, and anything interdisciplinary. When not writing, she enjoys making music, biking, and watching live tropical fish cams.
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