Armelle Rancillac, neurobiology researcher

How long have you been interested in studying the brain ?

I've always liked to understand. No matter what subject I'm working on, I need to get to the bottom of it. Maybe that's where I got my taste for science. I quickly became intrigued by genetics... and, later, by neurobiology. Neurobiology intrigued me more, because it allowed me to understand the very mechanisms of understanding.
After my final year in science, I went on to study biology at university. First to Orsay (Paris-XI) for the M1, then to Pierre-et-Marie-Curie (Paris-VI) for the DEA (M2) and PhD. My thesis focused on the cellular mechanisms of learning and memory. I uncovered new learning mechanisms in the cerebellum, involving star cells. Then, during my post-doctorate, I became interested in the cortex... and, after my recruitment at Inserm, my research focused on the hippocampus and the VLPO (ventrolateral preoptic nucleus). Let's just say that I wander around the brain according to the questions that come to me.

How do you organize your research ?

According to the emergencies ! And there are lots of them. I have no routine. Mostly, I plan my manipulations. But I'm not at the bench as much as I used to be... because I'm currently supervising two theses, I have to keep an eye on the literature, write funding applications and articles and also, and regularly, do expert work, which consists of proofreading articles or research projects. Not forgetting presenting our results at scientific conferences and popularizing my passion for science.

The PhD students help me a lot in my work. It's a real collaboration where we discuss what experiments we should do or how we should analyze our results to reach solid conclusions.

The study of the brain led you to the study of sleep..

Paradoxically, although a third of French people suffer from sleep disorders (which can lead to hypertension, diabetes, depression, Alzheimer's disease...), the mechanisms by which sleep functions are still poorly understood and very little studied !

What is your research focus ?

The human brain contains one hundred and billion neurons, as well as eighty-five billion glial cells. These cells are much less well known than neurons, as it took much longer to understand how they functioned and what their roles were. There are several types of glial cells, of which astrocytes form the majority, named after their star-like shape.

While neurons activate electrically, astrocytes communicate differently. They play on their calcium concentration. Like neurons, astrocytes are organized into networks, superimposed on those of neurons. The aim of my work is to understand how these different networks communicate with each other, and how they help regulate sleep.

In fact, astrocytes can capture glucose from blood vessels, which supply the brain with energy. Although the brain accounts for only 2 % of a person's body weight, it nevertheless consumes 20 % of the body's energy source, glucose. Neurons need a lot of energy to function. Glucose is mainly captured by astrocytes, which then feed the neurons by releasing another molecule, lactate. But the transformation of glucose into lactate by astrocytes also induces the release of adenosine, a very important molecule which promotes the activation of sleep-promoting neurons.

We've all had the experience of drinking coffee too late in the day and then suffering from insomnia. This is because the caffeine contained in coffee sits on the neurons that trigger sleep. Caffeine prevents adenosine, normally released by astrocytes, from binding to sleep-promoting neurons and thus activating them to induce sleep.

What do you deduce from these results ?

In the laboratory, we have already shown that astrocytes do not release the same amount of adenosine in response to glucose, whether in the morning on waking or in the evening before going to bed. Thus, by measuring adenosine levels in VLPO, the region that controls sleep, we were able to show that astrocytes released more adenosine in the evening, at bedtime, than in the morning. Taken together, our results suggest that eating a meal rich in glucose in the evening would promote sleep, whereas a meal richer in protein or fat would promote wakefulness. We are now investigating how changes in astrocyte shape during sleep/wake cycles might help to regulate the activity of VLPO neurons to a greater or lesser extent, and thus also play a part in sleep regulation.

Do your results have any applications ?

I sometimes work with the French Army. For a soldier, maintaining alertness is vital. For example, if we follow our findings, a fighter pilot, flying at mach 3, should opt for protein bars rather than sugar if he doesn't want to doze off !

You like to popularize your discipline..

I regularly give lectures and share some of my discoveries on social networks... Selfishly, this work of communicating with the general public nourishes me, because scientific writing intended exclusively for neurobiologists sometimes generates frustration : in form, because the vocabulary is limited and the syntax stereotyped, and in substance, because the research projects you have to write are short-term projections (three to five years).

Writing a novel of social anticipation, fed by my very neurobiological world(AlicE 2630: Expérience humaine, ed. CloniTech) was yet another way of freeing myself from these constraints.

In fact, I still enjoy sharing my passion as a researcher. It's a captivating profession, which gives researchers, when they observe and understand a particular mechanism for the first time, the unique and privileged sensation of being like the first man to walk on the Moon !

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Armelle Rancillac works in the Neuroglial Interactions in Cerebral Physiopathology team at the Collège de France's Centre interdisciplinaire de recherche en biologie, directed by Nathalie Rouach (Collège de France/Inserm).

Photos © Patrick Imbert
Interview by David Adjemian