Here comes the single-celled mouse embryo!

Multiscale analysis of single and double maternal-zygotic Myh9 and Myh10 mutants during mouse preimplantation development https://www.biorxiv.org/content/10.1101/2020.09.10.291997v1

This is the 2nd preprint of the lab!
We carefully analysed the phenotype of double maternal zygotic non-muscle myosin II KOs. A collective effort lead by @MSchliffka and @Fra_Torto, with a lot of help from @oozguc, @diane_pelzer, Ludmilla de Plater and Oliver Polzer.

So what happens when embryos don't have non-muscle myosin II? Obviously, they cannot contract and this makes it rather difficult to undergo cytokinesis. In fact they can fail all successive divisions and reach the blastocyst stage with 1 single cell instead of 32!

But it doesn't matter too much to the mouse embryo, which powers through its development as a single-celled embryo and tries anyways to form its first lumen with the trophectoderm-like structure that it can make.

Can't divide??
Keep calm and carry on to make a single-celled "blastocyst"

So during early mouse development, you basically don't need a tissue to accumulate the fluid destined to form the first lumen. To check this, we used a cool cell fusion assay to create more single-celled embryos.

Fused single-celled embryos also start inflating at the same rate as WT and mutant embryos. So basically, the fluid accumulation of the early mouse embryo is a programmed cell-autonomous process!

There are plenty of other aspects about early mammalian development and the relative contribution of different myosin paralogs explored in this study. So please check it out!