Apical extracellular matrix
The apical extracellular matrix (aECM) is widely present in the animal kingdom, and they can form a variety of structures that play a key role in regulating the interaction between organisms and their environment. Many aECMs show complex three-dimensional structures and have complex patterns at both the microscopic and nanoscale.
Currently, some well-studied examples of aECM include the collagen cuticle of nematodes, the chitin cuticle of arthropods, etc. Scientists have known that, in some cases, the pattern of aECM is directly related to the cytoskeletal pattern of the underlying epithelium. But in general, little is known about how complex patterns arise in aECM.
Now, a new study published in the journal Nature Communications reports that a team of scientists using advanced imaging instruments has finally revealed the basis of these substrates in a tiny nematode after years of hard work.
Decoding the Critical "Struts"
Caenorhabditis elegans is a model organism studied in the laboratory and has been extensively studied for decades. Due to their extremely simple, transparent bodies, researchers can easily peek inside their bodies and examine their skin.
At the same time, beneath the surface of these simple animals, they also have complex structures and possess nearly 20,000 genes, about the same number as human genes, so studying these nematodes could provide clues to the structure and function of more advanced organisms.
In the new study, the researchers deciphered the aggregation of aECM patterns in Caenorhabditis elegans at the nanoscale. Using a super-powerful, high-resolution microscope, they revealed never-before-seen patterns associated with "strut" and concluded that struts play a key role in the normal development and functional exercise of aECM.
In the cuticle of an adult Caenorhabditis elegans, each layer is connected by a pole. The struts are like small pillars that connect the different layers of the substrate and act as scaffolds.
3D images of "poles" (green) and collagen (magenta) were realistic. (Photo/ucsd.edu)
In the new study, the researchers focused on the exoskeleton, or cuticle, of Caenorhabditis elegans. They found that defects in the struts caused the fluid-filled medial stratum corneum to swell, or "blister."
Within the stratum corneum, they focus on collagen, the most abundant type of protein in the animal's body, which helps to keep body substances bound together. The struts connect the key layers together. Without these struts, these different layers would separate, leading to problems such as blistering. Under the microscope, the researchers observed that among the blistered mutants, no struts were visible.
A new paradigm for research
This result is made possible by the 3D structured light illumination super-resolution microscopy technique used by the researchers, which focuses on the brace with an amazing degree and makes it easier for the researchers to interpret the function of the struts. Prior to this, conventional laboratory instruments were not able to image the struts in detail, often resulting in unknown spots appearing in the frame.
Two types of nematode collagen labeled red and green under a super-resolution microscope. (Photo/ucsd.edu)
They analyzed the structure of the brace and the previously unknown pattern of the cuticle at the nanoscale. In this study, the researchers said, they could see exactly where the proteins went in those matrices. This result may be an exemplary study of how substrates are assembled into very complex structures and very complex patterns.
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