Home' Technology Review : November December 2007 Contents Q&A
TECHNOLOGY REVIEW /
William Hurlbut, a physician
and ethicist, is best known as
a member of the President s
Council on Bioethics. Though he has
spoken out against the destruction of
embryos for research purposes, he is
nonetheless a supporter of embryonic-
stem-cell research. He avoids what
would other wise be a terminal para-
dox through a proposal that he calls
"altered nuclear transfer," or ANT. His
goal: to create embryonic stem cells
without destroying human embryos.
One of the most promising meth-
ods for creating embryonic stem
cells is cloning: the nucleus of an egg
cell is replaced by the nucleus of an
adult cell, a process called somatic-
cell nuclear transfer. The egg is then
induced to divide, and the stem cells
har vested from the resulting embryo
are pluripotent, meaning they can
form any sort of tissue in the body.
But harvesting the stem cells destroys
the embryo. By contrast, ANT (which
has been shown to work in mice, if
not humans) switches o vital genes---
through alteration of the somatic-cell
nucleus, the cytoplasm of the egg, or
both---before the transfer takes place.
Hurlbut says the resulting cell mass
could not become an embryo but
could produce pluripotent stem cells.
Hurlbut recently spoke with
Michael Fitzgerald about ANT.
TR: What compelled you to come
up with altered nuclear transfer?
Hurlbut: When the President s
Council met [to debate the ethics of
stem-cell research, in 2002], it was
clear that both sides of this debate are
promoting important positive goods:
that on the one hand you have peo-
ple trying to defend human dignity
from its earliest stages, and on the
other hand you have people trying
to promote advances in science and
medicine. And as I sat there and lis-
tened to this debate, I thought, "Isn t
there an answer to this? Isn t there
some third option, some way that
both of these goals can be achieved?"
I thought of dermoid cysts, benign
ovarian tumors that produce all the
cell types, tissues, and partial organs
of the human body. Clearly some-
thing like embryonic stem cells is
being produced in those tumors. And
I thought to myself, "If nature can do
this, we can do it. There must be sim-
ple technological alterations we could
use in concert with nuclear transfer
such that we produced embryonic-
type, pluripotent stem cells, but
without producing the unitary organ-
ism that is a human embryo."
Does ANT produce truly pluri-
potent stem cells?
[MIT s] Rudy Jaenisch got pluri-
potent cells. He injected some of
the cells into living mice, and they
for med tumors with all the tissue
types in them. So yes, it works. The
next step with altered nuclear transfer
is to study it in primates. If it works
in primates, speci cally in rhesus
macaques, then we can proceed with
pretty good con dence, but also cau-
tion, in working with human cells.
How does mutating an embryo
so it is no longer a viable embryo
really solve the problem?
That is exactly the wrong way to
frame the description of what s being
done. The idea that we re mutat-
ing an embryo is an inaccurate and
misleading representation of what
we re doing. The key to the proj-
ect is that no embryo is ever created.
It s not a de ciency in an embryo
but an insu ciency in the start-
ing component, such that it cannot
rise to the level of a living being.
Shinya Yamanaka and others are hav-
ing success reprogramming adult
skin cells into embryonic stem cells.
Why should we continue with ANT?
Yamanaka s cells are very, very
interesting and may solve the issue
of how to procure embryonic-type
stem cells. But altered nuclear trans-
fer takes things back to the very
beginning, to the single-cell stage.
So ANT would give us the ethi-
cal framework and technological
tools for probing early develop-
ment, without the creation and
destr uction of human embryos.
Are there circumstances that
you could imagine under which
you might condone embryonic-
I m in no sense an opponent
of research with embryonic stem
cells as such. I have moral con-
cerns about how the stem cells
are obtained, not about the use of
the cells themselves. I m not in
favor of the destr uction of human
embryos for research purposes.
What are the ethical and moral
issues we face in neuroscience?
One of the most fundamental
questions is how you correlate the
neurological development during
embryogenesis with moral stand-
ing. Some people argue that until you
have a conscious being, or maybe a
self-conscious being, you don t have
moral value. We don t know exactly
what consciousness is, but most neuro-
physiologists don t think there s con-
sciousness present before 18 or 20
weeks at the earliest. If that s your
criterion, you could probably jus-
tify the instrumental use of human
embryos up to maybe 20 weeks. So
without a strong moral principle,
you may very well see the argu-
ment over stem-cell research move
from 14 days to later stages. So at
least at the federal-funding level, we
should preser ve the principle of the
defense of human life from its earli-
est origins in the one-cell stage.
Embryonic stem cells without embryos
Links Archive September October 2007 January February 2008 Navigation Previous Page Next Page