P.Z. Myers Blogs About Zhou Q, Brown J, Kanarek A, Rajagopa J, Melton DA (2008), "In Vivo Reprogramming of Adult Pancreatic Exocrine Cells to β-Cells," Nature Aug 27.
Hacking the Pancreas:
Pharyngula: This is a big deal, I think.... [T]his is a recent result published in Nature... basic science, not clinical work... this has a long, long way to go before it can be applied to humans....
The pancreas is... made up of a variety of different [kinds of] cells.... [T]here are exocrine cells, cells that produce quantities of important substances that are piped directly into the digestive tract via ducts.... [There are] endocrine cells... that generate hormonal signals that are secreted into the blood stream... the most familiar of these are the beta (β) cells, which are organized into clumps called islets and which secrete insulin....
What the researchers did was identify a small subset of transcription factors, the genes Ngn3, Pdx1 and Mafa, that are sufficient to switch on the insulin production genes in non-insulin-producing cells of the pancreas. They can turn exocrine cells into β cells... [by] insert[ing] the transcription factors (and a gene that makes a glowing protein, GFP, as a marker) into adenoviruses, and then inject[ing] the virus directly into the pancreases of genetically immunodeficient (to reduce immune response complications) adult mice. The viruses infected a subset of the pancreatic cells, preferentially the exocrine cells, and started pumping out the transcription factors.... [T]he use of viral transfection is perhaps the scariest part of the story; viruses aren't trivial to keep in check.... [T]hey also found that inducing the expression of the 3 transcription factors in other kinds of cells, like muscle, seems to do nothing. These genes are only potent in pancreatic cells that are already primed....
The virus is also not needed for long term maintenance of these cells.... [A]ll it takes is a brief jolt of expression of Ngn3, Pdx1 and Mafa to switch susceptible cells into the β cell state, and that the developmental program is then self-sustaining....
A lot of attention has been paid to embryonic stem cell and adult stem cell technologies, and those are both important and provide research and treatment opportunities that must not be neglected, but this is a third way: mastering the developmental control genes of the cell so that we can reprogram mature cells into any cell type we need.... This is the direction developmental medicine can take us — I hope you're all ready to support it.
