New method achieves healthy embryos without spermWomen already say that man is an appendix of the penis. As sex toys already replace the penis, only the sexual function remains. And when this will be gone, too, what will be men's fate?
If amongst vertebrates, only sharks and some lizards have been known to reproduce without requiring sperm for fertilization, a phenomenon called parthenogenesis ("virgin birth"), no mammal (thus species with a body structure like ours) is known to do this.
But now, a Japanese team has managed to bypass natural barriers, generating apparently normal mice by mixing the DNA of two mouse eggs. They did this by reprogramming one of the eggs to act more like sperm.
Unfertilized mouse eggs can divide in the lab, but these embryos can't form a placenta and die soon, and a missing male element is thought to cause this. Each chromosome carries genes, specifically activated or deactivated in connection with their inheritance from the mother or the father. Both maternal and paternal activations are required for a mammalian fetus for a healthy development.
The Japanese researchers led by Tomohiro Kono at Tokyo University of Agriculture in Japan have revealed that once the imprinting issue is bypassed, two normal female mice could produce healthy embryos. 2 important DNA patches involved in paternal imprinting were found on chromosomes 7 and 12.
The team engineered mutant mice lacking the genes involved in the paternal imprinting, allowing the female genome to act like a male one. Immature eggs taken from newly born mutant mice were inserted into the nuclei of normal mouse ovules. With these in vitro "fertilized" eggs started division, forming hollow cell balls of cells called blastocysts, the team inserted them into the wombs of female mice. 27 "bimaternal" individuals survived to adulthood, with a success rate equalizing that of in vitro fertilized human embryos, being healthy and fertile.
"It's remarkable that one need only modify two small regions of the genome to make an egg genetically behave like a sperm. So could such a technique potentially enable two women to have a biological baby? Out of the question," said co-author Anne Ferguson-Smith, developmental geneticist of the University of Cambridge, U.K.
"One of the women would have to be a mutant to donate the necessary genetically altered oocyte. Still, the technology should give scientists a new tool for better understanding how parental imprinting works and just how sperm contributes to development," she said.
"Because the mutant oocytes were immature, it is likely that they retained some of the imprinting from the mutant mouse's father. That would confuse any attempts to pin down exactly which imprinted genes are truly crucial for normal development.", warned Davor Solter of the Max Planck Institute of Immunobiology in Freiburg, Germany.