For the first time, a research shows that female eggs may not essentially be needed to create an offspring; scientists from the University of Bath have formulated a method that includes using sperm to fertilize embryos rather than eggs, and the method has resulted in the birth of healthy baby mice.
Senior author Dr. Tony Perry, from the Department of Biology & Biochemistry at Bath, and co-workers publish their results in the journal Nature Communications.
In the conventional sense, fertilization takes place when a sperm meets a female egg. Once this happens, the egg “reprograms” the sperm, whereby numerous chromosomal and DNA modifications occur that allow the sperm to split and generate the specialized cells that comprise an organism – a process identified as totipotency.
Since the fertilization process was initially unraveled in the late 1800s, researchers have long considered that only an egg has the capability to reprogram a sperm to be able to induce embryonic development.
Earlier researches have shown it is feasible to “trick” a non-fertilized egg into developing an embryo, developing what are known as parthenogenotes. However, because these embryos are absent of sperm, which is essential for development, they have not live through more than a few days.
Now, Dr. Perry and colleagues show that in mice, injecting sperm into parthenogenotes can spur full-term embryonic growth, resulting in the birth of healthy offspring.
Sperm does not depend on the egg to be reprogrammed
For their research, the investigators injected sperm nuclei into mice parthenogenotes that were chemically treated to contain a single set of unpaired chromosomes, as compared to a set of paired chromosomes that generally occur when a sperm meets an egg.
The study team identified the technique led to the development of healthy offspring, with around a 24 % success rate. In comparison, non-injected mice parthenogenotes developed no offspring, while a 2 percent success rate took place with nuclear transfer cloning.
Though inserted embryos had chromosomal and DNA resemblances to non-injected embryos, the researchers observe that the injected embryos confirmed various cellular processes.
This observation, they say, indicates that there are other ways in which sperm can be reprogrammed to induce embryonic development – that is, sperm is not solely reliant on the egg.
“It had been considered that only an egg cell was able to reprogram sperm to enable embryonic development to take place.
Our work challenges the dogma, held since early embryologists first observed mammalian eggs about 1827 and noticed fertilization 5 decades afterwards, that only an egg cell fertilized with a sperm cell can outcome in a live mammalian birth.”