For more than a century, biology textbooks have taught that animal cells must round up before dividing, producing two identical daughter cells. The team discovered that many cells – including human endothelial cells – can divide while remaining elongated, generating two daughter cells that are unequal in size and potentially in fate.  

The researchers call this newly characterised process ‘isomorphic division’. Unlike classical division, where a cell becomes spherical and splits symmetrically, isomorphic division allows elongated cells to maintain their shape and split asymmetrically. This creates one larger and one smaller daughter cell, often with different internal contents and developmental roles.  

According to the authors, “Distinct morphological changes switched cells to an ‘isomorphic’ mode… interphase morphology appeared to provide a geometric code defining mitotic symmetry, fate determinant partitioning, and daughter state.”  

The study involved live imaging of zebrafish embryos and experiments with human and mouse endothelial cells. One of the key findings was that this geometric code – based on a cell’s shape prior to division – is read by specialised intracellular components, particularly Rab4-positive endosomes. These endosomes help distribute cellular materials unevenly, influencing what each daughter cell becomes.  

This discovery carries significant relevance for regenerative medicine. If scientists can control the shape of a cell before it divides, they could potentially steer the identity of the resulting cells – an essential tool for tissue engineering and organ repair. Cells might be guided to divide in a way that produces a specialised type while also retaining a more primitive or supportive daughter, offering a precise method of building complex tissues.  

Dr Shane Herbert, co-author of the study, explained the importance of this insight in an interview with Phys.org: “This means that manipulating cell shape could be used not just to predict cell behaviour, but to actively design it.”