Human cells help researchers understand squid camouflage

Date:
March 27, 2023
Source:
American Chemical Society
Summary:
Squids and octopuses are masters of camouflage. But some aspects
of how they become reversibly transparent are still 'unclear,'
because researchers can't culture cephalopod skin cells in the
lab. Now, researchers have replicated the tunable transparency of
squid skin in mammalian cells, which are more easily cultured.


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FULL STORY ========================================================================== Squids and octopuses are masters of camouflage, blending into their
environment to evade predators or surprise prey. Some aspects of how
these cephalopods become reversibly transparent are still "unclear,"
largely because researchers can't culture cephalopod skin cells in
the lab. Today, however, researchers report that they have replicated
the tunable transparency of some squid skin cells in mammalian cells,
which can be cultured. The work could not only shed light on basic squid biology, but also lead to better ways to image many cell types.


==========================================================================
The researchers will present their results at the spring meeting of the American Chemical Society (ACS).

For many years, Alon Gorodetsky, Ph.D., and his research group have been working on materials inspired by squid. In past work, they developed "invisibility stickers," which consisted of bacterially produced squid reflectin proteins that were adhered onto sticky tape. "So then, we had
this crazy idea to see whether we could capture some aspect of the ability
of squid skin tissues to change transparency within human cell cultures,"
says Gorodetsky, who is the principal investigator on the project.

The team at the University of California, Irvine focused their efforts
on cephalopod cells called leucophores, which have particulate-like nanostructures composed of reflectin proteins that scatter
light. Typically, reflectins clump together and form the nanoparticles, so light isn't absorbed or directly transmitted; instead, the light scatters
or bounces off of them, making the leucophores appear bright white.

"We wanted to engineer mammalian cells to stably, instead of
temporarily, form reflectin nanostructures for which we could better
control the scattering of light," says Gorodetsky. That's because if
cells allow light through with little scattering, they'll seem more transparent. Alternatively, by scattering a lot more light, cells will
become opaque and more apparent. "Then, at a cellular level, or even
the culture level, we thought that we could predictably alter the cells' transparency relative to the surroundings or background," he says.

To change how light interacts with cultured cells, Georgii Bogdanov,
a graduate student in Gorodetsky's lab who is presenting the results, introduced squid- derived genes that encoded for reflectin into human
cells, which then used the DNA to produce the protein. "A key advance in
our experiments was getting the cells to stably produce reflectin and form light-scattering nanostructures with relatively high refractive indices,
which also allowed us to better image the cells in three dimensions,"
says Bogdanov.

In experiments, the team added salt to the cells' culture media and
observed the reflectin proteins clumping together into nanostructures. By systematically increasing the salt concentration, Bogdanov got
detailed, time-lapse 3D images of the nanostructures' properties. As
the nanoparticles became larger, the amount of light that bounced off
the cells increased, consequently tuning their opacity.

Then, the COVID-19 pandemic hit, leaving the researchers to wonder what
they could do to advance their investigation without being physically
in the lab.

So, Bogdanov spent his time at home developing computational models
that could predict a cell's expected light scattering and transparency
before an experiment was even run. "It's a beautiful loop between theory
and experiments, where you feed in design parameters for the reflectin nanostructures, get out specific predicted optical properties and then
engineer the cells more efficiently -- for whatever light-scattering
properties you might be interested in," explains Gorodetsky.

On a basic level, Gorodetsky suggests that these results will help
scientists better understand squid skin cells, which haven't been
successfully cultured in a laboratory setting. For example, previous researchers postulated that reflectin nanoparticles disassemble and
reassemble to change the transparency of tunable squid leucophores. And
now Gorodetsky's team has shown that similar rearrangements occurred
in their stable engineered mammalian cells with simple changes in salt concentration, a mechanism that appears analogous to what has been
observed in the tunable squid cells.

The researchers are now optimizing their technique to design better
cellular imaging strategies based on the cells' intrinsic optical
properties. Gorodetsky envisions that the reflectin proteins could
act as genetically encoded tags that would not bleach inside human
cells. "Reflectin as a molecular probe provides a lot of possibilities
to track structures in cells with advanced microscopy techniques," adds Bogdanov. For example, the scientists propose that imaging approaches
based on their work could also have implications for better understanding
cell growth and development.

The researchers acknowledge funding from the Defense Advanced Research
Projects Agency and the U.S. Air Force Office of Scientific Research.

* RELATED_TOPICS
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# Biology # Biotechnology # Molecular_Biology #
Biotechnology_and_Bioengineering
o Earth_&_Climate
# Environmental_Awareness # Environmental_Issues #
Sustainability # Environmental_Policy
* RELATED_TERMS
o Somatic_cell o Stem_cell o Octopus o Epithelium o
Intelligence_of_squid_and_octopuses o Itch o Giant_squid
o Camouflage

========================================================================== Story Source: Materials provided by American_Chemical_Society. Note:
Content may be edited for style and length.


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Link to news story: https://www.sciencedaily.com/releases/2023/03/230327114905.htm

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