What can I learn from worms?June 2012

Lesson 1: What is regeneration?

Stem cell-powered worm

For the tiny flatworm, regeneration of missing body parts is a piece of cake. Someone chopped its head off? No problem! It grows a brand new one in about seven days, complete with a spanking new brain with all the right circuits and connections. As for the chopped-off head, it just grows a new body, which is no small feat.

This amazing ability of the flatworm to regrow a missing head and to produce a brain on demand has now been traced back to a key gene called Smed-prep, researchers report in a study published in PloS Genetics. The identification of the gene is exciting news for scientists who wonder if humans, too, will one day manage to regenerate missing body parts. The Register reports that the discovery of the Smed-prep gene unlocks the mechanisms by which the hard-to-kill planarian flatworms grow new muscle, gut, and brain cells.

Even more importantly, it seems that the information contained in Smed-prep makes the new cells appear in the right place and organize themselves into working structures – as opposed to nonfunctional blobs of cytoplasm.

Lead researcher Aziz Aboobaker describes the worm’s regenerative superpowers: “One of the reasons they can do this is because they’re chock-full of stem cells. We estimate that at any time, in an adult worm, about 20 percent of its cells actually consist of stem cells, which are able to make any of the other cells in the body.This animal in nature just sort of crawls along the bottoms of lakes and rivers, and is constantly replacing its aging cells.”

The researchers say that studying these worms could eventually lead to regenerative therapies for humans who have lost function in a part of their body or even an entire limb. Aboobaker told The Register: “If we know what is happening when tissues are regenerated under normal circumstances, we can begin to formulate how to replace damaged and diseased organs, tissues and cells in an organized and safe way following an injury caused by trauma or disease. This would be desirable for treating Alzheimer’s disease, for example.”

/ Figure: Location of Smed-prep gene expression in planaria.
(B) Smed-prep expression in whole worms shows a distinct anterior (towards the head) domain of high expression.
(C) Staining (blue) to highlight the brain.
(D) Brain (blue) combined with false coloring of Smed-prep (red) expression. Note that protein expression extends outside of the brain.

Article and figure adapted from

Rao, Smriti. (2010, April 27). Stem cell-powered worm doesn’t age, can grow a new head. Discover Magazine Blog. Retrieved from

Felix, D.A. and A.A. Aboobaker. (2010). The TALE class homeobox gene Smed-prep defines the anterior compartment for head regeneration. PLoS Genetics 6: 4.

Guiding Questions

1. According to the study, what does the Smed-prep gene do?

2. What characteristics of planarians contribute to their ability to regenerate?

3. What implications might studies in planarians have on human health?

4. According to the Figure, where would you expect to find the Smed-prep protein?

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