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Meet the Community: Juan Burrone
By Carol Cruzan Morton
Juan Burrone is a postdoctoral fellow in the lab of Venkatesh Murthy, the Morris Kahn Associate Professor of Molecular and Cellular Biology.
Contrary to rumors that MCB postdoctoral fellow Juan Burrone had heard about the cutthroat atmosphere of big prestigious U.S. universities, the most competitive thing in his lab are the growing neurons he studies. The exception comes on Sunday mornings, when people from the neighboring lab are mostly interested in beating Burrone and his lab mates in their weekly basketball game, or at the Wednesday evening soccer game, when MCB graduate students and postdoctoral fellows line up against colleagues in the Department of Organismic and Evolutionary Biology.
“I find the environment relaxed,” Burrone says. “People are generally interested in helping you out when you need advice. You can approach other labs, and they’re genuinely interested in giving you a hand.”
As a graduate student at Cambridge University in England, Burrone studied short-term synaptic activity measured by electrophysiology techniques in the conveniently large synaptic terminals of goldfish retinal bipolar cells. Now in the lab of Venkatesh Murthy, Burrone takes the long view of synapse-to-synapse communication in mammals.
Much of the action takes place on glass coverslips. Nerve cells from the brains of young rats form neural networks invisible to the naked eye, but a squint through the microscope shows the delicate webs of axons that grow in a matter of weeks.
About four years ago, when Burrone arrived at Harvard, other researchers in the field had shown that groups of neurons could change their communication patterns to stay within an optimal range of activity. Synapse activity dropped to compensate for increased neuronal activity. Vice versa, synapses stepped up the cross-talk when researchers turned down the neuronal activity.
So Burrone experimented to find out what would happen to the synapse activity of a single inhibited neuron within a network of normally active neurons.
Synapses form at the many intersections of the neuronal meshwork of axons and dendrites as nerve cells race each other in the competition to establish a large network of connections. The critical nerve-to-nerve conversations necessary for living, breathing, and thinking take place at these synapses. Lit up in the microscope, active synapses along one neuron can resemble beads on a string woven through black lace.
As it turns out, conversational lapses by young nerve cells may permanently affect their social life in the brain, but the same gaffes in older nerve cells are accommodated. Using hippocampal cells from newborn rats, Burrone showed that if a quiet, inactive neuron effectively snubs its neighbor, it loses its chance to establish a synapse. But once a synapse has formed between neurons, researchers can only briefly interrupt the exchange of neurotransmitters before the neurons find a way to chat each other up again. The work was first published in the journal Nature two years ago.
“We found new forms of plasticity,” Burrone says. “To sum it up, if you inhibit a neuron before it can develop and form synapses, other neurons prefer not to synapse with it. There is an important window of time. If you inhibit the neuron after the synapses are formed, the neuron doesn’t lose the synapses. It compensates for the inhibition and overcomes it.”
When deciding on a postdoctoral position, Burrone admits, “I chose the Boston area because my fiancée had been accepted as a doctoral student in biology at the Massachusetts Institute of Technology. I joined the Murthy lab, then only a year old and still small, because Dr. Murthy was open to trying out new things and was full of ideas.”
The couple lives conveniently close to both of their labs. Every morning, Burrone walks down the street in one direction to the lab, and his wife, Maria, cycles to MIT, less than a mile in the opposite direction, where she is finishing her doctorate degree in biology. In October, they married in their native Argentina.
“We’re expecting our first child in July, and we’ve already named him Nicholas,” says Burrone. Soon, they will settle on their next major decision—where to live. “We’re considering the United States with its plentiful jobs and research support rather than Europe, especially the United Kingdom, where we have both lived before, or Spain and Italy, with their culture and lifestyle.”
In the meantime, Burrone is applying the genetic tools and imaging techniques to in vivo studies of the mechanics of competition in developing neurons to learn more about how the activity of the neurons directs the network of synapses. “I always feel like there are a hundred more things I need to be doing,” he says.
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