Humans, birds, and other creatures share a set of genes that lead to the development of fingers and other digits (like paws or wings), but the way those digits form has been a mystery. Now a group of researchers in Wisconsin have discovered the secret of digit growth, and perhaps the key to regrowing severed or stunted fingers. It's even possible this research would allow you to grow an extra finger or two. This might make working with your hands easier, or lead to strange biopunk fashions that involve fingers sprouting from your head.
The best part is that one of the genes involved in finger-creation is called Sonic Hedgehog:
The UW-Madison team showed that growth begins in a portion of the developing digit they have named the phalanx-forming region (PFR). They illustrated that phalanges, structures that later become finger or toe bones, arise not from cartilage cells but from mesenchymal cells. And they discovered that a complex array of signals from a variety of genes at different times combine to form each phalanx.
Though the research was done on chick digits, it may have implications for humans born with a genetic condition known as bradydactyly, or stubby fingers and toes. The work was undertaken in the laboratory of John Fallon, the Harland Winfield Mossman Professor of Anatomy at the SMPH, who for years has sought to understand how cell fate is determined and patterning-of digits, teeth and feathers-is achieved during embryonic development.
In birds and mammals, digits arise in the mitten-shaped autopod, or developing foot, which consists of two alternating regions. The digital rays, made up of cartilage and mesenchyme, become the phalanges in the adult chicken's toes. These alternate with the interdigits, also consisting of mesenchymal tissue, which fill the space between the digit rays and eventually regress.
Scientists know that the gene Sonic Hedgehog (SHH) plays an important role in determining the form and number of digits, and many believe that other secondary signaling centers downstream of SHH also are involved in establishing a particular digit's identity . . . Sean Hasso, Fallon's current graduate student, wanted to know precisely which cells in the digital ray give rise to phalanges and which molecular events determine the number, size and shape of each phalanx. Performing microsurgery and cell marking studies on the embryonic chick autopod, Hasso showed that the cells that eventually form phalanges arise from the growth of mesenchyme at the tip of the digital ray.
If we can learn to stimulate mesenchyme cells, we could promote the growth of new digits. No word on whether we can actually get human mesenchyme cells to grow wings or claws. Image via Marginalrevolution.
Wisconsin Researchers Describe How Digits Grow [Eurekalert]