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- From: Zweistein <exnihil@xxxxxxxxx>
- Date: Mon, 4 Feb 2008 12:25:35 -0800 (PST)
Are male eggs and female sperm on the horizon?
* 02 February 2008
* From New Scientist
* Peter Aldhous
"FEMALE sperm", "male eggs" and "same-sex reproduction" - whether
these terms fill you with hope or disgust, a reproductive revolution
is already in progress. In a handful of labs across the world,
biologists are trying to make genetically male cells develop into
eggs, and female cells into sperm. If successful, their efforts might
one day allow lesbian and gay couples to have children that are
genetically their own.
Now Greg Aharonian, a patent analyst from San Francisco, is trying to
patent the technologies that could make this possible. In part,
Aharonian's goal is to stimulate debate. He argues that lesbians and
gay men have a right to know about developments in biology that could
allow same-sex reproduction. Aharonian also wants to undermine the
argument that marriage should remain an exclusively heterosexual
institution because its main purpose is procreation. "I'm a
troublemaker," he admits.
In the US, where reproductive clinics are largely unregulated and
religious conservatives are at war with gay rights campaigners over
same-sex marriage, it should indeed cause controversy. Same-sex
reproduction is also an issue in the UK, where Parliament is debating
whether in principle to allow IVF using sperm or eggs grown in the lab
- although this would only apply to sperm from male cells, and eggs
from female cells (see "Gay couples left out").
Aharonian has not shown that the techniques he describes will actually
work - that is not necessary to claim ownership of an invention. In
his application, Aharonian discusses methods including the use of
artificial chromosomes and cellular "reprogramming" techniques. Still,
biologists want to see hard experimental evidence. "He claims things
that could be possible, but it needs experiments," says Karim
Nayernia, a stem cell biologist at Newcastle University in the UK.
Nayernia is working on lab techniques to make sperm from human stem
cells. In April last year, he made headlines by taking bone marrow
stem cells from adult men and making them develop into spermatogonia -
cells that can give rise to immature sperm through a process called
meiosis. Since then, Nayernia claims to have repeated the feat for
female bone marrow, opening the door for the creation of female sperm.
In so far unpublished work, Nayernia also claims to have made lab-
grown male spermatogonia enter meiosis by culturing them with Sertoli
cells - support cells from the testes that nurture developing sperm.
He has not yet succeeded in getting his female cells to do the same
but remains optimistic. "I think, in principle, it will be
scientifically possible," Nayernia says, although there will be
additional challenges along the way (see "Men not essential?").
"One researcher claims to have produced spermatogonia - the precursors
of sperm - from female bone marrow stem cells"
Male eggs might not be so hard to make, though. A Brazilian team led
by Irina Kerkis of the Butantan Institute in Saõ Paulo claims to have
made both sperm and eggs from cultures of male mouse embryonic stem
cells (Cloning and Stem Cells, DOI: 10.1089/clo.2007.0031). The
researchers have not yet shown that their male eggs can be fertilised
to produce viable offspring, but they are thinking about possibilities
for same-sex human reproduction.
"We are starting experiments with human embryonic stem cells," says
Kerkis. If these are successful, then the next step will be to see if
male eggs could be made from cells known as "induced pluripotent stem
cells". These seem to behave just like embryonic stem cells, and can
be made from adult skin cells using a genetic reprogramming technique
pioneered by Shinya Yamanaka of Kyoto University in Japan (New
Scientist, 24 November 2007, p 7).
If all these experiments pan out, then the stage would be set for a
gay man to donate skin cells that could be used to make eggs, which
could then be fertilised by his partner's sperm and placed into the
uterus of a surrogate mother. "I think it is possible," says Kerkis,
"but I don't know how people will look at this ethically."
Safety is another worry, especially given concerns that Yamanaka's
reprogramming technique might make cells prone to becoming cancerous.
Safety fears are also likely to surround female sperm, especially if
they are created with the help of artificial chromosomes, as Aharonian
suggests. "This looks like a very extreme kind of biological
manipulation," says Marcy Darnovsky of the Center for Genetics and
Society in Oakland, California.
Even if the safety issues could be resolved, same-sex reproduction
would remain politically controversial. Religious conservative groups
already oppose gay and lesbian adoption, claiming that children are
best raised by a mother and a father. And while such groups have used
the link between marriage and procreation to argue that homosexuals
should not be allowed to wed, techniques that allow gay and lesbian
couples to have their own biological children are unlikely to shift
their position.
"To the extent that there might be a right to reproduce, it would
apply only to natural reproduction," argues Peter Sprigg, vice-
president for policy with the Family Research Council in Washington
DC, a leading religious conservative group.
Miriam Yeung, until recently director of public policy and government
relations with the Lesbian, Gay, Bisexual and Transgender Community
Center in New York, predicts a mixed reaction among homosexuals: some
may be concerned about safety, others put off by the likely cost,
while others are content to have children using donated eggs or sperm.
"But there may be some in the community who really want this," she
says.
Debra Mathews, a bioethicist at the Johns Hopkins School of Medicine
in Baltimore, Maryland, agrees. She is a member of the Hinxton Group,
an international consortium on stem cell ethics, which in April is
organising a meeting near Cambridge, UK, to discuss issues raised by
efforts to grow sperm and eggs in the lab - including the likely
demand from homosexual couples. "People want children, and no one
wants anyone else to tell them that they can't have them," Mathews
observes.
"People want children, and no one wants anyone else to tell them that
they can't have them"
From issue 2641 of New Scientist magazine, 02 February 2008, page 6-7
Gay couples left out
In the UK, at least, same-sex reproduction seems likely to be ruled
out for the moment. The UK parliament is now debating changes to the
1990 Human Fertilisation and Embryology Act, and the government is
under pressure to include an amendment that would allow the future use
in IVF of eggs and sperm grown in the lab from stem cells. But
supporters of the proposed amendment say that this would only be used
to help infertile men produce sperm and infertile women make eggs - it
would exclude same-sex reproduction.
"Part of it is pragmatic," says Evan Harris, science spokesman for the
Liberal Democrats and one of the amendment's main backers. "This is
much more likely to be acceptable to Parliament." But he also argues
that the science behind using lab-grown sperm or eggs to help
infertile heterosexual couples looks much more promising than efforts
to create female sperm or male eggs.
The technology for same-sex reproduction may be at an earlier stage,
but one of the government's concerns is that, by excluding homosexual
couples, the amendment might be open to challenge under human rights
law.
Men not essential?
Creating sperm from women may not be impossible - but there are still
some formidable obstacles to overcome.
Most obvious is the lack of a male Y chromosome - which may contain
genes necessary for sperm formation, and without which all offspring
would be female. One way of overcoming this would be to add
"artificial chromosomes" bearing genes from the Y chromosome, suggests
Greg Aharonian in his patent application.
He also suggests a kind of "surrogate fatherhood", in which maturing
female sperm would be incubated in the testes of a male volunteer to
ensure that they gain the correct "imprinting" - chemical alterations
to DNA that modify the activity of genes in a developing embryo
according to whether they came from the sperm or the egg.
Nevertheless, some biologists feel that the obstacles to making female
sperm are huge. "I think it will take far more than 10 years," says
Robin Lovell-Badge of the National Institute for Medical Research in
London.
Another key problem relates to a phenomenon called "X inactivation",
in which one of the two X chromosomes in each of a woman's cells is
usually silenced. In the germ cells that give rise to eggs, it
reactivates. The same will happen in female cells that become
spermatogonia, the germ cells that form sperm, says Lovell-Badge. And
this, he argues, will block sperm formation at an early stage.
.
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