Written by Rebecca Brown.

During development, cells in the zebrafish embryo oscillate between solid and liquid state due to different pressures in environment – a process known as tissue ‘melting’.

Following almost a decade of research, Mongera et al. have shown that anterior-posterior axis elongation of the zebrafish embryo relies on such methods. Whilst cells at the head remain packed densely together, posterior cells move more freely around one another encouraging movement and resulting in sculpting and elongation of the tail.

Much like the process of ‘jamming’ in foams, the cells transition between solid and fluid state, creating cells which appear to ‘jiggle’. Thus, the culture is neither solid nor liquid, but exists somewhere in between as an amorphous solid. [This can be visualised in the solid-yet-flowing nature of toothpaste.]

Figure 1 (taken from Cepelewicz 2018): differing cell densities along the anterior-posterior axis of the zebrafish embryo.

Using techniques such as magnetically-responsive microdroplets, the authors measured stress forces along the axis and determined that cell shape changed from spherical to ellipsoid, indicating higher forces at the anterior end of the embryo. This has shown that elongation relies on the moulding of structures; think about glass blowing: the structure is malleable yet still retains its shape.

The applications of this are still to be known. Research needs to be conducted into the differences between 2D and 3D samples, in which correlation between yield force and cell-adhesion is not aligning. Furthermore, better understanding of what causes ‘jamming’ could eventually outline treatment options such as in preventing metastasising cancers.

Forget jingle bells, this is the time of jiggle cells!

Further Reading:

Mongera et al. 2018. ‘A fluid-to-solid jamming transition underlies vertebrate body axis elongation’. Nature:


Cepelewicz J. 2018. ‘‘Traffic Jams’ of cells help to sculpt embryos’. Quanta Magazine:


Lenne PF and V Trivedi. 2018. ‘Tissue ‘melting’ sculpts embryo. Nature (News and Views):


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