The rhythmic process is jumpstarted by a spike of calcium in cells in the end of the intestine. The initial spike triggers a wave of calcium through the remainder of the intestine, stimulating muscle contractions and forcing waste out of the worm's body. The team wondered what ensures that the wave always starts in the right place the end of the intestine as opposed to the middle or front?
"It's like dominos lined up in a row," said Erik Allman, Ph.D., a study author and graduate student in Nehrke's lab at the Medical Center. "We wanted to find out what provides the 'push' that topples that first domino and starts the sequence."
The team's analysis revealed that a molecule called a microRNA is required for the entire waste removal process to run smoothly. microRNA-786 is present in the two most posterior intestinal cells of worms and tags these cells as the pacemakers or leaders. These pacemakers dictate when and where the primary calcium spike occurs, activating the movement of waste through the worm's body. When the team removed microRNA-786 from worms the process went awry; the calcium wave started in the wrong place and the waste cycle was irregular and longer than normal.
"As a developmental biologist, I am interested in how cells become different from one another," said Abbott. "This microRNA acts to make the posterior cells different from their neighbors by changing the calcium signaling activity. This difference allows these cells to function as the pacemaker."
"What is really exciting here is that this particular microRNA appears to exert a subtle effect," added Nehrke. "Since calcium signaling is so ubiquitous, it is important to realize that fine tuning its output may be what helps to discriminate between its many biological functions. The next step is to find out if
|Contact: Emily Boynton|
University of Rochester Medical Center