Tops born from two fathers were born healthy, grown and become fathers in turn: a result that teaches us something more on reproduction.
For the first time in the studies on the reproduction between mammals, two mice obtained in the laboratory by two fathers were born healthy, grown up to adulthood and have generated a offspring in turn. They became dad, to try again that the unconventional origin had not compromised their fertility. The discovery published on Pnas It is the result of a job coordinated by Yanchang Wei, the Shanghai Jiao Tong University (China).
Two spermatozoa and an oocyte without nucleus
To obtain mice without a mother’s chromosomal kit, the researchers injected two spermatozoa into a cell egg of private mouse of the nucleus (where the maternal genetic heritage resides). Then, they used a technique called Editing of the epigenoma To reprogram the DNA of the spermatozoa on several sites, so that the embryos develop normally. They obtained 259 embryos that were transferred to mouse females, chosen to carry on pregnancies.
Only two embryos have given rise to healthy mice, both males. Once adults, the two mice coupled with some females and generated healthy mice.
What is genomic imprinting
In the past, fertile mice had already been created starting from two mothers, but so far the attempts to obtain fertile mice from two fathers had not given fruit. The embryos developed for some time, and then then stop completely: reason is a mechanism called genomic imprintingthat the new study helped to better understand.
Most animals have, in their cells, two complete series of chromosomes, each inherited from a parent. Genomic imprinting is the Modulation of the expression of genesdepending on that genetic material comes from the mother or father. The chromosomes received as a dowry from parents are provided with “chemical labels” capable of making certain genes active or inactive (epigenetic changes, because they do not change the DNA sequence). Epigenetic programming of egg or sperm cells is different: certain genes are active in male and inactive gametes in female and vice versa.
This mechanism represents A biological barrier to asexual reproduction Because, if a cell hosts two series of maternal chromosomes or two series of paternal chromosomes, due to genomic imprinting, it is missing the active copies of genes necessary for development, or it has active two copies where there should be one copy only.
The solution thanks to Crispr
The authors of the study have used a modified form of the Molecular Scissors Crispr to target seven specific Sperm DNA sites, removing or adding the “labels” that activate or deactivate the genes (called methyl groups) instead of altering the DNA sequence.
They thus obtained mice for the first time not only vital and healthy, as had already happened in the past, but even fertile in turnshowing that “genomic imprinting is the fundamental barrier to term development full of the unipine embryos of mammals ».
What do these results mean for man?
The new approach, which does not contemplate any genetic modification, could in principle represent a possible future path for homosexual couples who want to have children with their own genetic heritage. However, We are not even remotely close to this option: The very low reproductive success would require an exaggerated number of embryos and surrogate mothers, and there is the possibility that the regulation of genomic imprinting in humans steps for sites other than those identified for mice. The merit of the study is for now that of having increased our understanding of reproductive mechanisms in mammals.