Of mice and useless men; males not needed for procreation

Of mice and useless men
By Leigh Dayton, Science writer
22apr04

PROVING that males are a biological frill, Japanese and Korean scientists have created a healthy mouse born with no male genetic material at all.

It's a process called parthenogenesis and - until now - it's never happened in mammals, from mice to, well, men.
In contrast, many insects and reptiles, not to mention plants, take advantage of this all-girl form of reproduction.

"Because mammals are inhibited from reproducing by parthenogenesis (we decided to study) why sperm and eggs are required for normal development in mammals," team leader Tomohiro Kono said from his office at the Toyko University of Agriculture.

Professor Kono's group discovered that the stumbling block was a phenomenon called "genomic imprinting", a process that turns off either the male or the female version of a gene when eggs and sperm meet to produce an embryo.

It sounded esoteric but the finding - and the science that revealed it - was "remarkable", said embryologist Patrick Tam of Sydney University and Westmead's Children's Medical Research Institute.

According to Professor Tam, imprinting is linked to some birth defects.

Increased knowledge of how imprinting affects sperm and eggs is fundamental to "how we tackle (such) birth defects", Professor Tam said.

He was so impressed with the work, reported today in Nature, that he co-authored a special article for the journal with his CMRI and Sydney University colleague, David Loebel. In order to create the first parthenogenetic pup, named Kaguya, Professor Kono and his colleagues - from two other research institutes in Tokyo and Seoul and Korea's MacroGen company - "constructed" designer mouse embryos.

The ingredients included genetic material from adult mouse eggs mixed with mouse egg material lacking a single gene.

The researchers previously had learned that one gene affected 1000 of the 35,000 genes in a mouse. By knocking out the gene, they reversed all the effects of male imprinting.

"That's amazing," said Professor Tam. "Only one gene is all you need."

Ultimately, 371 hybrid eggs developed into embryos and were transferred to surrogate mums. One of the two resulting pups was sacrificed for genetic tests, while Kaguya was allowed to grow to adulthood.

She has mated and given birth to her own pups.