Come out, experts from the woodworks!
Neu5Ac and Neu5Gc are sugars found on cells present in nearly every mammal, from chimps to pigs. When scientists altered the genes of mice so that they couldn't produce them, the mice died. However, unlike our closest relatives, humans lack a gene that makes Neu5Gc. The gene is not gone, but rendered silent by a fatal mutation, one that occured approximately 500,000 ago. Now, note that it is illegal to produce any new embryonic stem cell lines. Any scientist will tell you that extant and legal human stem cell lines have been existing in calf serum and often on layers of mouse "feeder" cells for growth. As such, they are immersed in a bath of antigen and if re-introdcued would elicit a strong immune response. I.e. although of human origin, they would be treated as foreign cells if injected. It is likely they would be rejected if injected with today's techniques anyway, but this may represent another significant hurdle for research, one that could be sidestepped with more progressive policy. (Via The Regular
posted by willns
on Jan 24, 2005 -