Mice created without fathers
By Paul Rincon

The scientists combined two sets of chromosomes from different eggs
Scientists have created two female mice without fertilising the eggs they
grew from, the journal Nature says.
The eggs had two sets of chromosomes from two female mice, rather than one
from the mother and one from the father as in a fertilised embryo.

The phenomenon, called parthenogenesis, never occurs naturally in mammals.

Some researchers say the procedures may be applied to stem cell research,
but the scientists who carried out the work say it would not yet work in
humans.

Mammal difference

Tomohiro Kono and colleagues switched off a key gene in the donor eggs which
affected imprinting - a barrier to parthenogenesis in mammals.

"Insects can reproduce by parthenogenesis. Even chickens can be made to
reproduce by parthenogenesis. I wanted to find out why mammals are
different," Dr Kono of Tokyo University of Agriculture, Japan, told BBC News
Online.

The team injected the genetic material from immature mouse eggs into mature
eggs with their own set of chromosomes. They then "activated" the combined
eggs, prompting them to start growing as an embryo.

By blocking expression of a gene called H19 in the immature mouse eggs, the
researchers increased the activity of another gene called Igf2.

Igf2 manufactures a protein responsible for regulating growth in the
developing foetus.

These genes are said to be imprinted. Imprinting means that some genes are
working in maternal DNA but switched off in paternal DNA, or vice versa.
They are unequally expressed.

The genetic manipulation carried out by the researchers gave the genes a
more paternal character.

But as a result of this modification, just two out of 598 mice embryos made
it to full term.

Read the rest at BBC News Online
http://news.bbc.co.uk/2/hi/science/nature/3643847.stm

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