Tick, Tock, Biological Clock

My name is Amanda Loehr and I am working in Dr. Brandauer’s lab. I am studying circadian rhythms—biological processes that happen in about a 24-hour oscillation.

What are we doing?

Circadian rhythms were first discovered in the 1700s. French scientist, Jean-Jacques d’Ortous de Mairan observed that plants make daily leaf movements—what was interesting though was that these movements continued when the plant was in the dark with no exposure to sunlight. This gave scientists the first important clue into circadian rhythms: they happen even in the absence of external cues. The plant wasn’t moving in response to the sun, it was being controlled by an internal clock.

Although circadian rhythms are not controlled by external cues, they do align to external cues. For us, the light and dark cycle of day and night is the major external cue for our rhythms. For this reason, if we travel across time zones or work abnormal shifts we get jet lagged—our circadian rhythms are being disrupted.

Disruption of one’s circadian rhythms has been associated with many mental and physical disorders from depression to cancer. In Dr. Brandauer’s lab we are particularly interested in how circadian rhythm disruption relates to insulin sensitivity and the development of type 2 diabetes.

To do this, we have to study the molecular genetics of the circadian clock in mice. Since scientists have realized that circadian rhythms have a genetic basis, several proteins have been described that control this biological clock. CLOCK, BMAL1, NAMPT, SIRT, PER and CRY all interact to regulate each other as well as the “clock”.

How do the concentrations of these proteins change throughout the 24-hour cycle? What about mRNA expression? Do the oscillations differ between different tissues, like skeletal muscle, liver and adipose tissues? Do the 24-hour oscillations of the protein concentrations and mRNA expression differ when the mice are jet lagged? These are all questions we are working to answer.

Why are we doing it?

Understanding the circadian clock at the molecular level is imperative to understanding its relationship to the occurrence of many diseases. Many disorders have a ‘rhythmicity’—heart attacks are much more likely to happen first thing in the morning than any other time of day. There are clear physiological explanations behind this phenomenon but the biological clock controlling the physiology could shed some light on a more complete understanding.

How are we doing it?

We just underwent our first 24-hour long experiment. We collected 12 tissue samples from six mice every four hours for 24 hours. One major obstacle that we had to overcome was the fact that the mice could not be exposed to ANY light for the 24 hours that we were conducting the experiment. How are we supposed to get into the mouse room without letting light in? This is where mine and Dr. Brandauer’s woodworking skills came into play.

SAWWe spent a few days with a circular saw and a power drill, constructing a lightproof enclosure to go around the mouse room door. Making it 100% void of light was not an easy task, but after the use of black paint and lots of black gorilla tape we had made something we were very proud of.


Our 100% light-proof enclosure!

How are we able to see in a lightproof room? Infrared night vision goggles!


The night vision monoculars were not very easy to use!

After a lot of practice with dissection and tissue processing, we were ready for our 24-hour experiment. Lots of coffee, food, and a positive attitude took us a long way. 432 tissue samples were collected and will be processed during my last two weeks here. Hopefully our data reflects our hard work these past few weeks!


One thought on “Tick, Tock, Biological Clock

  1. Amanda,

    What a great writeup of your summer work with the mice. You gave such great background about circadian rhythms, I was anxious to keep reading.

    I love all the pictures of you making the dark room and with the monocular. Beautiful.

    You are a great writer and a careful scientist. Those are two roles that are important to have and use hand-in-hand. Here’s to your continuing to use your gifts to make the world a better place.

    Denise Krebs

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