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New Insights into the Development of Mammalian Nose Patterns
The intricate physical structures seen on the noses of various mammals, such as dogs, ferrets, and cows, have intrigued scientists for decades. A research team from the University of Geneva (UNIGE) has delved into the embryonic development of these unique patterns using advanced 3D imaging techniques combined with computer simulations.
The study reveals that the distinct geometric patterns, comprising networks of grooves and polygons, arise from differential growth in skin tissue layers. This growth is supported by the network of blood vessels below, marking a significant advance in understanding how such structures develop. The detailed findings are documented in the journal Current Biology.
Natural patterns are visible in many species, from the stripes of zebras to the spots of cheetahs and even the spiral arrangements of pine cones. These diverse forms emerge through various morphogenetic processes responsible for shaping organisms during their developmental phases.
Some patterns arise through self-organization driven by chemical interactions, as articulated in Alan Turing’s reaction-diffusion theory. This model explains how certain biological patterns can form through the diffusion and interaction of chemical substances. Conversely, other shapes, like the folds in the human brain, result from mechanical constraints during growth, where faster-growing layers create complex structures.
Exploring the Morphogenesis of Noses
The research led by Professor Michel Milinkovitch in the Department of Genetics and Evolution at UNIGE is aimed at deciphering how developmental mechanisms contribute to the remarkable diversity of life. According to Milinkovitch, “It is quite straightforward to find beautiful patterns in nature; our study centers on the unique polygonal structures observed in the noses of canines, ferrets, and bovines.”
The rhinarium, or the naked skin of the nose in many mammals, displays this polygonal network, which plays critical roles such as retaining moisture and aiding in the collection of pheromones and other odorants.
To conduct their study, the Geneva team collaborated with multiple institutions, including Université Paris-Saclay and the École Nationale Vétérinaire d’Alfort (EnvA), acquiring rhinarium samples from embryos of these mammals.
Advanced Imaging Techniques
Utilizing light sheet fluorescence microscopy, the researchers were able to visualize the morphological features in three dimensions. Their observations confirmed that the characteristic polygonal networks begin to emerge during embryogenesis and are precisely aligned with the stiff network of blood vessels located in the dermis, the layer beneath the epidermis. Furthermore, the study noted that epithelial cells exhibit a faster rate of proliferation compared to those in the dermis.
The Role of Blood Vessels in Structural Formation
Building upon their observations, the team developed a mathematical model that simulates tissue growth, factoring in the varying growth rates of the epidermis and dermis, their stiffness, and the influence of blood vessels. Post-doctoral fellow Paule Dagenais explained, “Our simulations demonstrate that the mechanical stress from fast-growing epidermal layers is focused around the underlying vessels, which act as rigid supports. This dynamic leads to the outward expansion of the epidermis, forming dome-like structures similar to arches rising from solid pillars.”
This groundbreaking work illustrates how the positioning of the polygonal structures in the skin is influenced by the underlying vascular system, leading to the distinct formation of grooves and domes during nose development. “The concept of ‘mechanical positional information’ we identified has not been previously described as a mechanism for embryonic structure formation, but we anticipate it will enhance our understanding of various biological structures tied to vascular systems,” Milinkovitch concluded.
More information: Paule Dagenais et al, “Mechanical positional information guides the self-organized development of a polygonal network of creases in the skin of mammalian noses,” Current Biology (2024). DOI: 10.1016/j.cub.2024.09.055
Citation: “3D imaging study shows how geometric mechanics shape the dog’s nose” (2024, October 22) retrieved from Phys.org.
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phys.org