Gene editing has allowed researchers at the Chinese Academy of Sciences to reproduce mice with two sets of same-sex parents, one bi-maternal and the other bi-paternal.
In a study published by the Cell Stem Cell journal, the researchers have announced that the offspring of the bi-maternal parents are healthy, and have even gone on to have pups of their own. However, the ‘two-dads’ mice have not fared so well, and have died within days of their birth. This is the first time in history scientists have achieved same-sex reproduction.
Mammals can only reproduce through sexual reproduction, but the same rule does not apply to the rest of the animal kingdom. Certain fish, reptiles, and amphibians can reproduce through a process known as parthenogenesis.
The purpose of this project was to figure out which rules of reproduction needed to be broken to enable same-sex reproduction.
In the double mum’s case, the researchers took an egg from one mouse and a type of cell known as a haploid embryonic stem cell from another. They then used gene editing to delete three sets of genetic instructions to make them compatible with one another.
However, things were more complicated on the bi-paternal front.
To make bi-paternal reproduction possible, the researchers had to use a sperm, a male haploid embryonic stem cell, an egg that had all of its own genetic information removed and delete seven sets of genetic instructions.
The study suggests that the reason mammalian reproduction requires a male and female is that DNA behaves differently depending on which gender it came from. Consequently, without a set of male and female DNA, in utero development can be highly problematic. This is due to genomic imprinting, a process that imprints DNA in sperm and eggs with ‘stamps’ that alters how they function.
The parts of DNA carrying these stamps are the ones scientists had to delete in order to make the birth of the baby mice viable.