Unravelling How Planaria Regenerate
Planarian flatworms are one of nature’s little wonders. Although their ‘cross-eyed’ appearance is endearing, their real claim to fame comes from their regenerative ability. Split a planarian down the middle and you’ll soon have two cross-eyed critters staring back at you; cut one up and each piece will regenerate an entire flatworm. How do they pull of such an incredible feat? In 2011, researchers discovered that planarian regeneration depends on the activity of stem cells (‘neoblasts’) distributed throughout the flatworm’s body, but important questions about the process have remained unanswered. Are certain stem cells responsible for each organ? What activates the stem cells when regeneration is needed? An enterprising team of scientists at the Stowers Institute for Medical Research has brought us closer to answering these questions by developing a new technique to study planarian regeneration and using it to discover some of they genes involved.
Regeneration isn’t a uniquely planarian trait; starfish are well-known for growing back lost body parts, and even humans can regenerate to some extent (think of a wound healing). Planarians certainly excel at it, though; a flatworm can recover from being cut up into a staggering 279 tiny pieces, each of which regenerates into a new worm! Here’s a fun conundrum for those inclined to such things: which worm, if any, can claim to be the ‘original worm’? What if it were only two pieces instead of over 200? Would it make a difference if the two pieces were different sizes?
Undeterred by such philosophical considerations, the researchers used custom microarrays to identify genes which are activated when a planarian regenerates.