Latest news with #YanchangWei
Yahoo
26-06-2025
- Science
- Yahoo
Scientists Edited Sperm to Bypass an Egg. The Result? A Mouse With Two Dads.
"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." Here's what you'll learn when you read this story: The first mice to be created from two fathers, a phenomenon known as androgenesis, have now produced healthy offspring for the first time. Researchers implanted two sperm in an egg with its nucleus removed and modified the sperm with epigenome editing, turning certain genes on and off. This process carries a high risk, but it could be used for human reproduction and saving endangered species in the future. Millions of years of evolution have determined how mammals reproduce, but if something doesn't occur in nature, it is not necessarily impossible. It could still be achieved in a lab. Mammalian reproduction usually needs one sperm and one oocyte (egg) to create a zygote that develops in the womb until it becomes a new organism. Embryogenesis and fetal development in mice and humans are similar, which is why mice are often used as prototypes for human experiments. Also like humans, mice, at least on their own, cannot create a viable zygote out of two eggs or two sperm. That is where genetic intervention comes in. Earlier this year, researcher Yanchang Wei at Shanghai Jiao Tong University in China succeeded at creating mouse embryos from two sperm cells that were implanted into an egg after its nucleus had been removed. Giving the embryo a chance at survival meant making alterations to seven sites in the sperm DNA. The embryos grew inside surrogate mothers, but only two of over two hundred made it to adulthood. Those two mice have now reproduced successfully, showing that it is possible for at least one kind of mammal with two biological fathers to have healthy offspring of its own. 'Mammals are diploid creatures,' Wei said in a study recently published in PNAS. 'Every cell in their body contains two sets of chromosomes, one from the mother and one from the father. Mouse embryos with only paternal genomes can not develop to term, even being diploid (with two sets of chromosomes).' Behind what appears to be a miracle is a method known as epigenome editing. Because the epigenome is made up of chemical compounds that give the genome directions by modifying it, the process involves editing proteins, DNA and RNA at specific locations in the genome. There is no actual change to the genome made in epigenome editing, just a shift in which genes receive chemical signals to activate or inactivate them. There are some genes in sperm and eggs that are automatically switched on or off. Wei and his team used modified CRISPR proteins to turn on genes in the sperm cells that eggs would have normally had turned on. Androgenesis is rare among animals. While its does occur among some species of invertebrates, amphibians and fish. This phenomenon can happen when females produce eggs without a nucleus, which are then fertilized by males. The embryos will only inherit the genes of their father. In another type of androgenesis, both a sperm and egg form a zygote, but the genome of the female is eliminated. Males essentially use the eggs to clone themselves. It is thought that (with the exception of hermaphroditic organisms such as clams) androgenesis did not evolve much because the population would be dominated by male genes to the point of extinction. Creating mice from two mothers is easier in comparison. Known as parthenogenesis or 'virgin birth,' this phenomenon has been seen in reptiles, amphibians, insects, fish and even California condors. In 2004, a Japanese research team succeeded in genetically modifying and birthing the first fertile parthenogenic mouse, Kaguya. Whether genetically modified androgenesis or parthenogenesis will succeed in humans remains to be seen. The high risk is currently prohibitive. In the future, it might be a viable option, and could also be used to save critically endangered species which may only have a few individuals of one sex remaining. Never say 'impossible.' You Might Also Like The Do's and Don'ts of Using Painter's Tape The Best Portable BBQ Grills for Cooking Anywhere Can a Smart Watch Prolong Your Life?
Times
24-06-2025
- Science
- Times
Scientists create fertile mice with two fathers for first time
Scientists have created fertile mice from male genetic material alone, a breakthrough that could one day open the door to human babies who inherit their genes from two fathers. The experiment, led by Professor Yanchang Wei at Shanghai Jiao Tong University in China, marks a milestone in the quest to overcome the biological barriers to same-sex reproduction. The research, published in the journal PNAS, involved inserting DNA from two sperm cells into an egg that had been emptied of its nucleus. This resulted in an androgenetic embryo — one that contains only male genetic material — which was then implanted into the uterus of a surrogate mother mouse. In mammals androgenetic embryos typically fail early in development due to a phenomenon known as genomic imprinting. Roughly speaking, this refers to how certain genes are turned on or off depending on whether they came from the mother or father, via chemical modifications or 'epigenetic tags' that are attached to their DNA. Wei and his colleagues overcame this by using an editing technique to 'reprogramme' seven regions of the DNA of one of the sperm cells placed inside the egg. Epigenetic tags were altered to restore the genetic balance normally achieved by having input from a male and a female. Out of 259 embryos implanted into female mice, only two male pups survived to adulthood. Though the success rate was low, both males went on to have healthy offspring with female partners — the first time this has been achieved with two-father animals. The science is still in its early stages and there is no prospect of human babies being born with two fathers in the near future. However, the implications may be profound. • 'Motherless' mice created from embryos with only male genes Unlike some previous attempts to produce same-sex mammalian offspring, the technique used involved editing only the epigenetic features that control the activity levels of genes, rather than the genes themselves. This may makes it more useful for future clinical applications. However, the extremely low success rate of the technique used in the study would require an unacceptable number of eggs and surrogate mothers. One reason for the low success rate is that combining two sperm increases the odds of producing embryos with two Y chromosomes, which cannot develop. The epigenetic reprogramming also only worked fully in a fraction of the embryos. In 2004, Japanese researchers created a female mouse from two mothers — a breakthrough at the time. But producing viable offspring from two sperm has proven far more complicated, requiring a deeper understanding of imprinting. If the technique were ever adapted for use in humans, such children would technically still have a 'third parent' in the egg donor, whose mitochondrial DNA would remain in the embryo. However, they would inherit their nuclear DNA, which contains the vast majority of their genetic code, from two men.
