The cilia, which twirl at 10 cycles per second, were too fast for conventional video recording and so the scientists captured their complex movement on a specially adapted high-speed video moving at 500 frames per second.
"The net result is that the clockwise rotation of the cilia is converted into a right-to-left current over the embryo," said Ibaes. "The leftward current then acts as an amplifier, translating the ciliary dynamics into a large effect that covers a wide region of the embryo."
The Salk team suspected that the purpose of the cilia 'pump' was to concentrate messenger proteins on the left side of the embryo. This would, in effect, set up a chemical gradient that would tell developing cells whether they were on the right or left side of the body. Using proteins labelled with fluorescent tags, the researchers demonstrated that the cilia pump was capable of transporting proteins of a similar size to known chemical messengers. It took about 4 seconds for the test proteins to be whisked across the pinhead-sized primitive embryo.
Belmonte said that the next step is identifying the chemical messengers involved in the right-left flow and decoding the messages that they carry. "This study not only gives us a fascinating insight into why we are asymmetric; it may also be at the root of how the human body plan is built," he said.
The Salk Institute for Biological Studies i
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Contact: Cathy Yarbrough
yarbrough@salk.edu
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Salk Institute
19-May-2005