‘True hybrid’ mice might reveal how new species emerge

Amazing stuff!

"... To explore this question, the researchers crossed two different mouse species by creating zygotes that had the nuclear material and cytoplasm from both male Mus domesticus mice and female Mus spretus mice. They crossed different species as the contributions from each parent’s cytoplasm might be more apparent than taking the same approach in a male and female of the same species.

When a domesticus male is naturally bred with a spretus female, the females do not produce offspring. But through the researchers’ blended zygote technique — an approach the researchers have dubbed “true hybridization” — offspring were born, indicating something in the male cytoplasm was able to overcome this reproductive barrier. ..."

From the abstract:

"Interspecies hybrids have nuclear contributions from two species but oocyte cytoplasm from only one. Species discordance may lead to altered nuclear reprogramming of the foreign paternal genome. We reasoned that initial reprogramming in same species cytoplasm plus creation of hybrids with zygote cytoplasm from both species, which we describe here, might enhance nuclear reprogramming and promote hybrid development.

We report in Mus species that
(i) mammalian nuclear/cytoplasmic hybrids can be created,
(ii) they allow development and viability of a previously missing and uncharacterized hybrid class,
(iii) different oocyte cytoplasm environments lead to different phenotypes of same nuclear hybrid genotype, and
(iv) the novel hybrids exhibit sex ratio distortion with the absence of female progeny and represent a mammalian exception to Haldane’s rule.

Our results emphasize that interspecies hybrid phenotypes are not only the result of nuclear gene epistatic interactions but also cytonuclear interactions and that the latter have major impacts on fetal and placental growth and development."

‘True hybrid’ mice might reveal how new species emerge | YaleNews "Creating zygotes from the genetic material and cytoplasm of two mouse species yields offspring that differ drastically from their parents, a new study shows."

Creation of true interspecies hybrids: Rescue of hybrid class with hybrid cytoplasm affecting growth and metabolism (open access)

Fig. 1. Control single pronuclear and novel true interspecific hybrid zygotes are created as schematized.