Amazing stuff!
"... However, the study reveals that cell rounding is not a universal feature of cell division and is not how it often works in the body.
Dividing cells, they show, often don’t round up into sphere-like shapes. This lack of rounding breaks the symmetry of division to generate two daughter cells that differ from each other in both size and function, known as asymmetric division.
Asymmetric divisions are an important way that the different types of cells in the body are generated, to make different tissues and organs.
Until now, asymmetric cell division has predominantly only been associated with highly specialised cells, known as stem cells.
The scientists found that it is the shape of a parent cell before it even divides that can determine if they will round or not in division and determines how symmetric, or not, its daughter cells are going to be.
Cells which are shorter and wider in shape tend to round up and divide into two cells which are similar to each other. However, cells which are longer and thinner don’t round up and divide asymmetrically, so that one daughter is different to the other.
The findings could have far reaching implications on our understanding of the role of cell division in disease. For example, in the context of cancer cells, this type of ‘non-round’, asymmetric division could generate different cell behaviours known to promote cancer progression through metastasis. ..."
From the editor's summary and abstract:
"Editor’s summary
As tissues assemble, the dynamic shape changes that define their form occur coincident with the asymmetric cell divisions that generate cellular diversity. Lovegrove et al. used morphometric analyses of tissue formation in multiple contexts, including zebrafish, human, and mouse blood vessel and neural crest development, finding that these morphogenetic events are fundamentally co-dependent. Distinct shifts in shape-switched cells to a so-called “isomorphic” mode of division, which preserves premitotic shape and the unequal distribution of identity determinants throughout division. This switch, which avoids the usual cell rounding associated with division, breaks symmetry and creates daughter cells that adopt disparate identities. Thus, shape change sculpts tissue architecture and tunes the mode, symmetry, and outcome of cell division to direct identity decisions driving tissue building. ...
Abstract
During tissue formation, dynamic cell shape changes drive morphogenesis while asymmetric divisions create cellular diversity. We found that the shifts in cell morphology that shape tissues could concomitantly act as conserved instructive cues that trigger asymmetric division and direct core identity decisions underpinning tissue building. We performed single-cell morphometric analyses of endothelial and other mesenchymal-like cells.
Distinct morphological changes switched cells to an “isomorphic” mode of division, which preserved pre-mitotic morphology throughout mitosis. In isomorphic divisions, interphase morphology appeared to provide a geometric code defining mitotic symmetry, fate determinant partitioning, and daughter state.
Rab4-positive endosomes recognized this code, allowing them to respond to pre-mitotic morphology and segregate determinants accordingly.
Thus, morphogenetic shape change sculpts tissue form while also generating cellular heterogeneity, thereby driving tissue assembly."
Shifts in interphase cell morphology tune the mode and symmetry of mitosis.
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