By:
Michelle Bayefsky
Late last
month, the Cellular, Tissue, and Gene Therapies Advisory Committee of the Food
and Drug Administration (FDA) met to consider whether research on mitochondrial
donation, which could be used to prevent women from passing on mitochondrial
disease to their children, was ready to begin testing in humans. Instead
of excitement at the prospect of eradicating mitochondrial disease, which can
cause blindness, dementia, epilepsy, and many other conditions, much of the
public reaction was characterized by fear, confusion, and hostility. Headlines
from “Genetically Modified Babies” to “Tinkering with Frankenstein: Obama Admin
Considers Three-Parent Embryos” flooded the internet, and scientists and
bioethicists struggled to refocus attention on the medical feat that is close
to being achieved.[1]
Mitochondrial
donation involves either transferring healthy mitochondria from a donor into
the egg of an affected woman, or inserting the pronuclei of two prospective
parents into an enucleated donor egg.[2] Since
mitochondria carry their own DNA and are maternally inherited, children born
after mitochondrial donation will technically have DNA from three people –
hence the nickname “three-parent IVF” given to the procedure by the
press. This nickname is misleading, however. The degree
to which genetic parentage should be considered synonymous with parentage has
already been questioned in debates regarding egg and sperm donation, surrogacy,
and adoption. “Three-parent IVF” suggests a complicated family
situation which would be not at all necessary; if social and legal norms have
been successfully established for donating gametes containing nuclear DNA to
couples with infertility, surely the same could be accomplished with donating
mitochondrial DNA. Furthermore, it seems highly unlikely that we
would come to view the donor of mitochondria, an organelle about which most
members of the public have little knowledge, as a parent on equal footing with
the parents who contribute nuclear DNA and/or intend to raise the resulting
child.
Aside
from the question of parentage, the major source of controversy surrounding
mitochondrial donation is the fact that the technique constitutes a germline
modification; the donated mitochondrial DNA would be passed down from
generation to generation. Previously, a line has been drawn (in law,
in some countries) between gene therapies that treat problems in somatic cells,
like muscular disorders, and modifications that are heritable. Though
mitochondrial donation is aimed at preventing disease, some worry that it will
open the door to other types of germline modifications and the creation of
‘designer babies.’ These concerns are misplaced for two reasons.
First, it
is unclear why the somatic-germ cell distinction in gene therapy should be our
primary criterion rather than a distinction between healing and
enhancing. If our problem with the creation of designer babies –
which, given the current state of reproductive medicine, embryology, and
genetics is a very long way off – has something to do with satisfying
petty parental preferences, we should focus our efforts on preventing the use
of powerful reproductive procedures for insufficiently serious purposes. We
should debate what counts as the prevention of a serious genetic condition and
what counts as enhancement, not ban germline modifications that are aimed at
eradicating disease and reducing suffering.
A second
reason that the emphasis on germline modification is misplaced is that
technology is already available to select, if not modify, embryo’s genes. Pre-implantation
genetic diagnosis (PGD) is a technique that is used to test embryo’s genes
during in vitro fertilization, before deciding which embryos
to transfer into the woman’s uterus. PGD can be used to select
against serious heritable diseases, but it can also be used to select for sex,
milder disabilities such as deafness or dwarfism, and children who can serve as
tissue donors for sick siblings. The US has no laws or regulations
on the acceptable usage of PGD, and elective sex selection is relatively
common.[3] It
seems inconsistent to object to the use of mitochondrial donation to prevent
serious diseases when a technique that uses selection, rather than
modification, to choose non-medical characteristics of future
generations is currently unregulated and in use.
Finally,
if we decide that the germline criterion must continue to be respected, even
when using genetic modification to prevent disease, we could require that
mitochondrial donation only be used to create male embryos. We could
use sperm sorting to select male sperm which would be combined with a female
pronuclei and an enucleated egg with healthy mitochondria. Since
mitochondria are inherited maternally, if only males are created, the
mitochondrial DNA would not be passed on to the next generation. Though
many people find sex selection objectionable, there is precedent for performing
sex selection for medical purposes. For example, PGD is sometimes
used to select female embryos to avoid passing on X-linked disorders.
It is
understandable that new developments at the intersection of reproductive
medicine and genetic technology raise concerns about our attitudes towards
future generations, especially given the history of eugenics. However,
we should regard mitochondrial donation for what it is – a tool designed to
allow mothers suffering from mitochondrial disorders to have children to whom
they are genetically related – rather than focusing on potential future abuses
in the general area of genetics and fertility. Though it is
important to exercise caution in the modification of heritable genes, the
distinction between healing and enhancing should be our primary criterion for
deciding what techniques are ethical and permissible.
Michelle
Bayefsky is a senior at Yale University, where she was elected to Phi Beta
Kappa and founded and serves as Editor-in-Chief of the Yale Bioethics Journal.
After working as a research assistant at the Yale Interdisciplinary
Center for Bioethics for over two years, she will graduate in May with a B.A.
in Ethics, Politics and Economics.
[1] Last
week, the UK’s Human Fertilisation and Embryology Authority, the governmental
body responsible for regulating reproductive medical care, released draft
guidelines that would permit mitochondrial donation in humans. Children of
mitochondrial donation could be born in the UK as early as next year. See Telegraph article here.
[2] Lewis,
Ricki. "FDA Considers Mitochondrial DNA Replacement." Medscape
Medical News. Medscape, 26 Feb. 2014. Web. 09 Mar. 2014.
<http://www.medscape.com/viewarticle/821115>.
[3] Ginsburg,
Elizabeth S., Valerie L. Baker, Catherine Racowsky, Ethan Wantman, James
Goldfarb, and Judy E. Stern. "Use of Preimplantation Genetic Diagnosis and
Preimplantation Genetic Screening in the United States: A Society for Assisted
Reproductive Technology Writing Group Paper." Fertility and
Sterility 96.4 (2011): 865-68.
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