What happened
- Three researchers, Serrano Nájera, Delahaye and Steventon, published on 6 November 2026 in PNAS a study on how cells choose a strategy for elongating the body axis.
- They used gastruloids, aggregates of stem cells that model elongation of the posterior axis in mammals and in which environmental cues can be controlled in the laboratory.
- When gastruloids float free, they self-assemble a single posterior body axis, presumably through cell-cell interactions.
- When plated on laminin, an extracellular matrix protein, they acquire a flat morphology, break symmetry multiple times and produce several independently elongating cell streams, with anterior-posterior polarity, through collective migration.
Why it matters
- It is known that altering environmental cues can induce alternative morphogenetic programmes. What was not known is what determines the strategy cells use in each environment.
- The work shows that substrate availability determines which force-generation strategy cells employ to build the axis.
- Distinguishing between forces and genetic signals helps interpret early development experiments.
The number
No change in gene expression. Transcriptomic analysis shows that inhibiting formins blocks elongation on laminin with no detectable transcriptional changes. According to the authors, those cytoskeletal components play primarily a mechanical role that is only required when cells engage a substrate.
Context
On laminin, formin activity and focal adhesion-mediated traction are required for tissue elongation. In floating conditions, both are dispensable. That is, the same outcome, an elongated axis, is achieved with different machinery.
Laminin also biases cells towards posterior migratory fates, although similar Hox gene expression is preserved. The underlying genetic pattern holds, and what changes is the way of moving.
Gastruloids are a model and not an embryo, and the abstract does not claim the same happens in a mammalian embryo. What it offers is a demonstration that a single tissue can build its shape by different mechanical routes, depending on what it finds beneath it.
At Mamífero we follow developmental biology. We reported that having more cells with two X chromosomes eases Turner syndrome in the brain and that the brain removes neurons with highly altered genomes around birth. Also that capsids assembled in a test tube carry gene editors to dystrophic muscle and that a hypothalamic RNA slows the decline in sperm quality.
What’s next
- Checking whether these mechanical routes also appear in embryos would be the next step.
- Testing other substrates and other extracellular matrix proteins would show how many strategies exist.
- Morphogenesis models will have to include the mechanical context, besides genetic signals.
Bottom line
A tissue that elongates does not always need the same machinery. Changing what lies beneath the cells is enough for them to switch method without switching genes.
Sources
- Serrano Nájera, Delahaye and Steventon, “Gastruloids reveal alternative morphogenetic routes for body-axis elongation with distinct cytoskeletal dependencies”, PNAS, 6 November 2026, DOI 10.1073/pnas.2606813123. This note is based on the paper’s abstract.
- Cover image: Linda Bartlett (Photographer), Public domain, via Wikimedia Commons
Edited by Rodrigo Cornejo. How we select and verify: who writes these notes.
