It took Adam's rib to produce a female companion, but University of Hawaii scientists needed just the tip of a mouse tale to create the first male clone.
Researchers Teruhiko Wakayama and Ryuzo Yanagimachi, who introduced the Honolulu Technique for cloning mice a year ago, have used the technique to produce the first male mice clones. Their report appears in the June issue of the journal Nature Genetics.
Like Dolly the sheep, Cumulina and the scores of subsequent mice clones produced at the University of Hawaii at Manoa are female. All were produced from cells related to the female reproductive system; a mammary gland cell was used to create Dolly and cumulus cells, which surround developing eggs within the ovaries, used to clone the mice. Even cattle cloned in Japan are reported to come from cells related to the femal reproductive system. To create male mice, UH scientists have now used cells taken from the tip of adult male tails.
In the Honolulu Technique, the nucleus extracted from a donor cell is injected into enucleated egg from a separate female (an egg cell from which all genetic information has been removed). The eggs are activated to begin dividing and the developing embryos transplanted into a foster mother.
The technique produced three live male offspring from tale-tip cells late last fall. Two died shortly after birth, but the surviving clone, dubbed Fibro because the cultured tale-tip cells resemble fibroblasts, has developed normally and mated successfully, producing two healthy litters.
"When we produced mouse clones last year, people asked if it could be done with males. We knew that females, males made no difference," said Yanagimachi, a professor of anatomy and reproductive biology in UH Manoa's John A. Burns School of Medicine. Although only three in 274 transplanted embryos reached full term, Yanagimachi called the low survival rate "a barrier that still can be overcome."
The research is important because it shows that animals of either sex can be cloned and that somatic cells (non reproductive cells) can be used. "Precious animals of either sex"for example, endangered species and transgenic animals "can be propagated by cloning, irrespective of their fertility status," the Nature Genetics article concludes.