Are males actually needed for reproduction? Possibly not, but it is certainly easier with them
The first baby conceived through in-vitro fertilization (IVF), a process by which an egg is combined with sperm outside the body, in a lab, was born in 1978. The revolutionary process has been perfected over the years, entering regular medical practice and resulting in the birth of five million babies since.
As always in science, once you overcome one obstacle, new questions emerge. One of the most interesting ones is, is sperm truly essential for fertilization to occur, or can it happen without it? If the sperm and egg can be combined in a lab to create a fetus carrying DNA from both cells, then why can’t one egg fertilize another, giving rise to a fetus from two mothers?
Researchers from Tokyo University decided to test this in mice. The first experiments did not go well: The fertilized egg developed for several hours, but the placenta, which nourishes the embryo, did not. In another experiment, they fertilized an empty egg with two sperm cells, so that all the DNA came from the sperm donors. In this case, the placenta and outer embryonic tissue developed, the embryo itself did not.
The disappointing results did not discourage the researchers. Rather, it motivated them to find out what prevents a fertilized egg from developing into a fetus. Their persistence paid off, and, following several years, 460 attempts, and ten live births, one mouse lived to maturity. In an article published in Nature in 2004, the researchers, led by Tomohiro Kono, presented Kaguya – the first mouse born of the merger of genetic material from two eggs, with no father. Kaguya was born healthy, developed well, and matured, eventually giving birth to her own offspring.
Where was the problem?
It turns out that during gamete (the egg or sperm cell) formation, some genes go through genomic imprinting, which enables them to identify their source cell as male or female. As a result, the gene will be inactive, even though the DNA sequence does not change.
In nature, a gene from the father “silences” the parallel gene from the mother under certain conditions, and vice versa. This process is required for the proper development of both fetus and placenta; that’s why embryos originating in two female or male genome systems do not develop properly.
The researchers simulated the situation in nature by manipulating genes H19 and Igf2, which are essential for the development of the embryo and the placenta. H19 is expressed in the regular female chromosome and Igf2 is silenced in it. In the male chromosome, it’s the opposite. Since the researchers only used egg cell nuclei, they omitted H19 in one of them, which caused Igf2 to be expressed, as happens in natural fertilization.
Kids with no father?
When will two females be able to have children without a male? Probably not any time soon. At least not using the method in which the Japanese mouse was conceived. The process with humans is much more complicated, and if we don’t silence the right genes, or silence the wrong ones, genetic changes will occur that won’t enable proper fetus development. Moreover, there is an ethical dilemma in every process that involves genetic manipulation of human egg cells.
The solution could come from a study published in December 2014 in Cell, in which a research team led by Yaqub Hanna from the Weizmann Institute and Azim Surani from Cambridge University presented a breakthrough in the field of reproduction. For the first time, they created human stem cells from which sperm and egg cells can develop. These cells could have the potential to become genetically matching mature sperm and eggs for patients. In the future, it may be possible to develop new treatment methods in the field of reproduction based on this, and even enable a woman to reproduce with another woman.
In the video: A report from Sky News on the attempt to develop egg and sperm cells artificially