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Researchers find that cells building the face emerge from a program highly conserved across jawed vertebrates, but different facial architectures arise from distinct behaviors of the cells´ derivatives.
To the Point:
• Ancient blueprint: cells building the face emerge from a deeply conserved program across all jawed vertebrates
• Key difference: the divergence in facial development originates in the altered behavior of the cells´ derivatives
• New model system: small-spotted catshark allows the identification of conserved and divergent components of ancient developmental programs
• Information-rich resource: the study provides a high-resolution molecular and 3D atlas of facial development in a cartilaginous fish representative, the small-spotted catshark
Most of what scientists know about face development comes from studies in bony vertebrates such as mice, chickens, and zebrafish. However, their evolutionary counterparts, cartilaginous fishes, have remained largely unexplored. This gap has limited our understanding of how facial structures evolved at the origin of jawed vertebrates.
To address this, the research team led by Dr. Markéta Kaucká at the Max Planck Institute for Evolutionary Biology studied the small-spotted catshark (Scyliorhinus canicula). By combining single-cell transcriptomics with high-resolution molecular and synchrotron radiation µCT imaging, the researchers tracked the development of cranial neural crest cells—the cell population responsible for building the face.
The architects of the vertebrate face
Cranial neural crest cells are a transient population of multipotent cells unique to jawed vertebrate embryos that play a central role in building the head and face. They originate at the border of the neural plate (future brain) during early development, then delaminate from there and migrate to specific regions of the embryo. There, they differentiate into a wide range of tissues, including much of the craniofacial skeleton, cartilage, connective tissue, and parts of the peripheral nervous system. Because of their broad developmental potential and key role in shaping facial structures, cranial neural crest cells are considered a major driver of vertebrate head evolution.
A shared blueprint across 400 million years
The researchers found that cranial neural crest cells in sharks, which diverged from bony vertebrates more than 400 million years ago, follow a developmental program that closely resembles that of bony vertebrates. These cells emerge and migrate in a highly conserved manner. This indicates that the fundamental “blueprint” for face formation was already established early in jawed vertebrate evolution and has been maintained across diverse lineages.
Where divergence emerges: changes in cell behavior
Despite this shared foundation, the study reveals a crucial source of variation: the behavior of neural crest derivatives (daughter cells). In the catshark, neural crest cell progenies first gather and wait behind the eye and do not move to the front of the developing face, as in the mouse or chicken. Importantly, these cells still give rise to equivalent anatomical regions later on, suggesting that similar outcomes can be achieved through different developmental routes.
“We expected that the unique shark facial morphology arises from distinct properties of CNCC; however, that is not the case,” says Dr. Elio Escamilla-Vega, the first author of the study. “The core genetic program of CNCC is remarkably conserved, and instead, the dynamics and behavior of the derivatives are the main difference.”
Why this remained hidden until now?
“Shark embryos develop for several months in a firm egg case, where they are well-sheltered from the environment. This makes it difficult to apply methods that researchers routinely use in other model organisms, such as lineage tracing in mouse and zebrafish or dye tracing in chicken. This is one of the main challenges of working with such a unique non-model organism,” says Dr. Kaucká. The researchers collaborated with DESY (Deutsches Elektronen-Synchrotron), Dr. Jörg Hammel, and used synchrotron radiation micro-computed tomography to understand early development in the catshark. “Using tissue contrasting combined with attenuation-based X-rays, we can reach cellular resolution images of developing sharks in 3D,” says Dr. Jörg Hammel from DESY. When combined with staining for different genes, the researchers could reliably segment out cells, tissues, and organs in developing catshark embryos and understand the cellular dynamics throughout development.
The researchers deposited all data to make them available to the research community. “Catshark is becoming more frequently used in research,” says Dr. Escamilla-Vega, “but compared to traditional research organisms, its development is still largely unexplored. We wanted to provide these resources to the scientists, because there is still so much interesting information to mine”.
This research has been funded by the Max Planck Society and DESY (Hamburg, Germany), a member of the Helmholtz Association HGF (proposal I-20230087).
Dr. Markéta Kaucká
Max Planck Research Group Leader
Max Planck Institute for Evolutionary Biology
Max Planck Research Group Evolutionary Developmental Dynamics
Elio Escamilla-Vega, Andrea P. Murillo-Rincón, Louk W. G. Seton, Ann-Katrin Koch, Stella Kyomen, Carsten Fortmann-Grote, Jörg U. Hammel, Timo Moritz, Markéta Kaucká; Developmental dynamics of catshark cranial neural crest cells provide insights into gnathostome facial evolution. Development 1 May 2026; 153 (9): dev205258. doi: https://doi.org/10.1242/dev.205258
In yellow, developing skeletal elements in the catshark.
Source: Elio Escamillo
Copyright: Elio Escamillo
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