How to regrow your head

From Nature:

Knocking out a single gene can switch on a worm's ability to regenerate parts of its body, even enabling it to grow a new head. The fact that such a simple manipulation can restore healing abilities provides new insight into how the stem cells involved in this process are marshalled in animals. Some animals, such as salamanders and newts, can regenerate entire body parts, and mice can regrow toes if left with enough nail (see 'How nails regenerate lost fingertips'). Yet other species, including humans, merely produce scar tissue after an amputation. A trio of studies published on Nature’s website today^1–3 offers new clues as to what is behind these differences. All three studies looked at Wnt genes, which code for a series of enzymes that relay information from outside the cell to the nucleus, eventually producing proteins called β-catenins, which regulate gene expression. Wnt genes occur in all animals, but the studies looked at their roles in planarian flatworms. Some planarians can completely regenerate from small body parts such as their tails, whereas other flatworm species have more limited regenerative abilities.

Scientists already knew that the Wnt genes are expressed in a gradient along the worms' bodies — from high at the tail to low at the head — and suspected that the genes were involved in directing stem cells during healing. In the latest studies, researchers wanted to find out if a lack of Wnt gene expression was responsible for the poorer regenerative abilities in particular worm species. When these species are sliced apart at a point more than halfway to their tail ends, they can regenerate a tail from the head piece, but the tail section is unable to form a new head. However, if the wound is closer to the head — not more than about one-third of the way from it — then both parts will fully regenerate. To explain the disparity, Jochen Rink, a molecular biologist at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany, sliced a worm called Dendrocoelum lacteum at different positions along its body. He and his team then sequenced RNA from the various wounds¹. The researchers found that, in wounds that did regrow heads, genes coding for a series of enzymes involved in the Wnt pathway had their expression turned up. But in the pieces that couldn’t regrow, the Wnt genes “didn’t even twitch”, Rink says.

More here. (Note: For dear friend and fellow scientist Dr. Stavroula Kousteni whose brilliant insights into the b-catenin signaling in cancer cells is helping me develop novel and individualized therapy for my MDS patients)