Saturday, August 06, 2005

Stem cells, cloning and beginning of life

The stem cell debate and cloning was again in the news this past week. A South Korean team announced that they had successfully cloned a dog (a very cute Afghan named Snuppy). Dogs had been notoriously difficult to clone and the team only obtained one success in one thousand tries. This work shows that it is just a matter of time before primates including humans will be cloned.

In terms of therapeutic promise, this research implies that someday we will be able to extract genetic material from a person and create a blastocyst from which embryonic stem cells could be harvested. These cells would be pluripotent and potentially be able to replace or repair any tissue in the body. Additionally, they would be a complete genetic match to the donor eliminating the chance of rejection and the need for immunosuppressive drugs which have many side effects.

In order to make this work we first need to understand how to manipulate stem cells to create desired cell types. Right now we have very little understanding of what causes differentiation in cells. Implanted stem cells could possible replace damaged neurons but they could also become tumor cells. Currently, federal funding is restricted to research only on established embryonic stem cell lines. Unfortunately, many of these lines may be contaminated with other genetic material or damaged from repeated replication. While the rest of the world is pushing forward the US is beginning to lag behind.

However, the tide may be turning. In May, the US House voted overwhelmingly to repeal the ban on creating new stem cell lines. This past week, US Senate majority leader Bill Frist, shifted his position and is now supporting a bill to expand federal funding of stem cell research although the president is threatening to veto the measure.

The argument against the use of embryonic stem cells and cloning is the same as that against abortion and that is the destruction of an embryo is tantamount to taking a human life - the premise being that life begins at conception. The curious thing is that those that support this position don't seem to have a problem with in vitro fertilization where many eggs are extracted and fertilized to create an embryo but only a few ever make it to term. The rest are either frozen, donated or discarded.

That aside, the notion of a well defined moment where life begins is not so clear cut. Is it the moment that the sperm fuses with the egg or the moment that the formed zygote implants in the uterus? If it's the former, then why not make it the moment the sperm collides with the egg or even the moment the sperm will inevitably collide with the egg. Given that we now know any cell in the body can become a new life form, should we prohibit the destruction of any cell? Should we go further and prohibit the destruction of human genetic material of any form including the sequence itself?

Someday, the only thing we'll have left of monarch butterflies, giant pandas or blue whales will be the sequence. Currently, we can build a virus starting from just the genetic map but eventually we will be able to reconstruct any life form. What protection should the genetic code have when it's erasure implies the extinction of an entire species? Perhaps in the distant (or not so distant) future, we will reproduce entirely algorithmically. A computer could combine the sequences of two people and generate the genetic material for their child. Suppose there were only one copy of that sequence and it were destroyed. Would that be murder? When biology fully merges with computer science, how do we define life then?

1 comment:

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