Expert: Florence M Rollwagen - 5/9/2008

Question
How does a starfish regenerate limbs? Like what are the steps it takes to actually carry out regeneration as far as DNA replication and such?

Answer
Hi Jade:  Thanks for your question.  

Starfish are able to regrow parts of their body because they have stem cells that are totipotent.  That means that the stem cells contain all the information needed to differentiate into adult cells.  As soon as the starfish loses a limb, the cells next to the lost part receive a signal to start dividing.  This is the DNA replication part of your question.  Cells are constantly in contact with each other via cell surface receptors.  The receptors give the cells information about where they are and what functions they need to perform in terms of protein synthesis, etc.  Loss of cell signalling often trigger cell division.  

Step two is for the stem cells to decide what cell they will become.  This is a difficult question to explain, because scientists don’t know all the answers yet.  But as I said above, cells receive information that helps them decide what to become.  Part of this process is the turning on or off of HOX genes, which govern cell growth and maturation.  In other words, cells that are differentiated into, say, skin cells, revert to a more basic cell where they can become other cells.  These steps are governed by the activation and deactivation of specific genes.  

Here are a few citations you can use:

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=dbio.section.4360

http://www.ncbi.nlm.nih.gov/pubmed/11782076

These are some heavy-duty science articles, so if you need some help with them, just write back.

FM Rollwagen, PhD