How genes harnessed physics to develop organisms

The original version to This story Featured in Quanta Magazine.

Sip a glass of wine, and you’ll notice the liquid constantly dripping down the wet side of the glass. In 1855, James Thomson, brother of Lord Kelvin, He explained in Philosophical magazine These “rips” or “legs” of the wine result from the difference in surface tension between the alcohol and water. “This fact affords an explanation for many very strange movements,” Thompson wrote. He did not realize that the same effect, later called the Marangoni effect, might also shape how embryos develop.

In March, a group of biophysicists in France I mentioned The Marangoni effect is responsible for the pivotal moment when a homogeneous mass of cells elongates and develops a head-tail axis – the first distinguishing features of the organism it will become.

This discovery is part of a trend that challenges the norm in biology. Typically, biologists attempt to describe growth, development, and other biological processes as the result of chemical signals stimulated by genetic instructions. But that picture often seemed incomplete. Researchers now increasingly appreciate the role of mechanical forces in biology: forces that push and pull tissues in response to their physical properties, directing growth and development in ways that genes cannot.

Modern imaging and measurement techniques have opened scientists’ eyes to these forces by flooding the field with data calling for mechanistic explanations. “What has changed over the past decades is actually the possibility of watching what is happening live, and seeing the mechanisms in terms of cell movement, cell rearrangement, and tissue growth,” he said. Pierre François Lin from the University of Aix-Marseille, one of the researchers behind the latest study.

The shift toward mechanistic explanations has revived interest in pre-genetic models of biology. For example, in 1917, the Scottish biologist, mathematician, and classics scholar Darcy Thomson published On growth and shapeWhich highlighted the similarities between the forms found among living organisms and those appearing in non-living materials. Thompson wrote the book as an antidote to what he believed was an excessive tendency to explain everything in terms of Darwinian natural selection. His thesis—that physics also shapes us—is coming back into fashion.

“The hypothesis is that physics and mechanics can help us understand biology at the tissue scale,” he said. Alexander Kaplaa physicist and engineer at the University of Cambridge.

The task now is to understand the interplay of causes, where genes and physics somehow work in tandem to sculpt organisms.

Grow with the flow

Mechanistic models of embryo and tissue development are not new, but biologists have long lacked ways to test these ideas. Just seeing the fetuses is difficult; They are small and diffuse, bouncing light in all directions like frosted glass. But new microscopy and image analysis techniques have opened a clearer window on evolution.

Lin and his colleagues applied some new techniques to monitor the movement of cells inside mouse ventricles: bundles of stem cells that, as they grow, mimic the early stages of fetal development.