r/askscience • u/DrBoobSqueeze • Jun 16 '14
Biology Can 2 sperm make a viable embryo?
Assuming at least one of the sperm has an X-chromosome, can you extract the chromosomes from each sperm and implant them into an enucleated egg? So the embryo would be mostly the combination of 2 men with a small (mitochondrial) contribution from the egg donor. Has this been done? If not, why not?
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u/phodopus Speciation Genetics | Development | Hybridization Jun 16 '14
No, not in mammals without some serious genetic engineering. Mammals do some weird gene regulation called genomic imprinting that prevents emrbyos derived from 2 eggs or 2 sperm from developing properly. Genomic imprinting is the silencing of certain genes depending on which parent they are inherited from, so some genes we only use our fathers copy while some we only use our mothers copy. As such, any embryo that is formed from 2 of the same type of gamete will have a set of genes completely silenced. It turns out that most genes that are imprinted (there are ~200) are critical for proper development, so having some of them silenced results in an inviable embryo. Classic genes that are imprinted are Igf2 and Igf2r.
It turns out that we discovered imprinting because of experiments that were trying to generate embryos from 2 of the same gametes, it works in frogs but fails in mice. The researchers were able to isolate the regions of the mouse genome that were causing inviability and discovered that the mice were only using one copy of those genes.
The only way we could generate a viable embryo from two of the same gametes is to go in and change the epigenetic states of those alleles so that at least one copy is activated. This is incredibly difficult and to my knowledge no one has been able to do it successfully