Dr Peter Nagy, from Reproductive Biology Associates, Atlanta, collaborating with the University of Connecticut, USA, told the European Society of Human Reproduction and Embryology annual conference that former approaches to haploidisation[1] using a fully mature oocyte and a resting (interphase) somatic cell had caused misaligned chromosomes during cell division. However, he was confident from his team's latest experiments that this difficulty could be overcome, even though their new approach also ran into some problems.
"We decided to initiate haploidisation at an earlier stage in the oocyte's cell cycle, when it was still immature, but this time using a somatic cell in its active (metaphase or G2/M) stage. Essentially, we took the control of the first nuclear division away from the oocyte and gave it to the somatic cell," he said.
The US-Brazilian research team[2] , working with mouse cells, removed the nucleus of the immature oocyte, then transformed the somatic cell from its diploid (46 chromosome or 2n) stage to its next (4n) stage and transferred it to the immature enucleated oocyte (ooplast).
"What we expected by doing this was that the DNA in the somatic cell would condense into chromosomes inside the somatic cell not in the ooplast and that the somatic cell would direct the chromosome alignment and initial spindle formation, which would then be normal. The nucleus of the somatic cell, at its second stage of division and correctly assembled, would then undergo chromosome segregation in the ooplast, resulting in twice its diploid nuclear content during in-vitro maturation. As a result of an artificia
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Contact: Margaret Willson
m.willson@mwcommunications.org.uk
44-0-536 772181
European Society for Human Reproduction and Embryology
1-Jul-2003