The mice born from unfertilized eggs represent a new achievement in reproductive science. These laboratory-born rodents, containing only maternal genes, have grown to adulthood and successfully reproduced, generating subsequent generations—a feat previously thought impossible in mammals.
A team of researchers has successfully raised an adult mouse born from an unfertilized egg. This is known as asexual reproduction, or parthenogenesis, which occurs naturally in some animal species, including certain sharks, lizards, and birds. It produces a female that contains half or all of the genetic material from its mother, without requiring any genetic contribution from male gametes.
Successfully raised an adult mouse born from an unfertilized egg.
The authors wrote: “The success of reproduction in mammals opens up many opportunities in agriculture, research, and medicine. Identifying and editing additional ICRs that mark control regions can improve the efficiency of genetic development.”
A previous study attempting to induce reproduction in animals through parthenogenesis failed due to a lack of gene imprinting. In normal sexual reproduction, females receive two copies of a gene, one from each parent. However, the absence of gene imprinting—where certain genes are chemically tagged to indicate their parental origin—results in only one copy of the gene being expressed.
In the latest study, scientists utilized CRISPR gene-editing tools to target seven of these imprinted gene regions and altered various sections to make it appear as if the maternal genetic code came from a male. They then injected an enzyme into the egg to activate certain genes and mimic a process similar to that of an egg fertilized by a male.
Biochemist Tony Perry from the University of Bath in the UK stated: “This will become an important part of the puzzle regarding the mechanisms of very early embryonic development and how the two parental gene sets are regulated. Secondly, it serves as a significant technical proof of concept for the efficacy of these CRISPR tools.”
The researchers transferred 192 heterozygous gene embryos into 14 female mice, resulting in three live births, but only one mouse survived to adulthood. This mouse had a normal body weight at birth, but as an adult, it weighed about 20% less than the control mice in the study. Nevertheless, this mouse was still able to reproduce normally with males.
Marisa Bartolomei, a molecular biologist at the University of Pennsylvania who was not involved in the research, remarked: “I think there will be people who look at this and say, how is this possible? Can it replace reproduction? Reproduction without men seems hard to believe.” However, it could aid in the study of diseases caused by gene imprinting, such as Prader-Willi syndrome or Beckwith-Wiedemann syndrome.
We hope to continue necessary research in the future to improve the processes and success rates of viable offspring generations.
