Mouse embryonic germ cells and male gametes created ...( eutic cloning Daley adds. In therapeu...)

eutic cloning, Daley adds. In therapeutic cloning, scientists take a cell from an adult animal, such as a skin or blood cell, remove its nucleus, which contains all the genes, and place that nucleus inside an egg whose own nucleus has been removed. This process of nuclear transfer creates an early embryo and somehow - no one knows quite how - erases the genetic markers instructing the cell to differentiate. If scientists could learn how the erasure happens, it might be possible to create stem cells capable of generating all tissues without having to obtain a donor egg for cloning, and without having to create a new embryo - in fact, without having to clone at all.

MALE GAMETES
In the second phase of the research, the investigators asked whether the germ cells could be coaxed into becoming functional gametes - reproductive cells -- under laboratory conditions.

Earlier this year, Hans Schler and colleagues from the University of Pennsylvania reported being able to make female gametes -- eggs -- from mouse embryonic stem cells. However, these eggs so far have not proven capable of being fertilized by sperm. Daley's team worked on the other side of the reproductive equation, creating male gametes, or primitive male sperm.

The researchers used the same embryoid bodies that generated the embryonic germ cells, but this time, they grew the bodies for two to three weeks, allowing the germ cells to mature into male gametes that could be isolated in the lab. These gametes were not full-fledged sperm - for instance, they had no tails. However, when Kitai Kim, Ph.D., a postdoctoral fellow in Hematology/Oncology at Children's Hospital, and Kevin Eggan, a Junior Fellow in the Harvard Society of Fellow, injected the gametes into eggs, the gametes fertilized the eggs and fused their DNA with that of the eggs, creating embryos with full sets of chromosomes.

The researchers now plan to take the next step, transferring these ea
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Contact: Mary Ellen Shay
mary.Shay@tch.harvard.edu
617-355-6420
Children's Hospital Boston
10-Dec-2003

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