After scientists study cat embryos in depth, uncover the amazing origin of unique markings on tabby cats

 

Among nearly 60 million pet cats across the United States, classic striped tabby is particularly popular.

Taggy stripes originated from the direct ancestor of domestic cats, the Near East Wildcat.

According to National Geographic (written by JOANNA KLEIN: Zhong Huiyuan): After scientists studied cat embryos in depth, they uncovered the amazing origin of this unique marking on domestic cats.

Among the nearly 60 million pet cats in the United States, one of the most popular is the classic tabby - it is a kind of stripes, dots and vortexes, and the cat's forehead also has a fur color that looks like a capital M.

Although tabby cats are so popular (think Garfield), scientists know very little about how their unique appearance comes from.

In a study published last Monday in the journal Nature Communications, scientists observed that the genes that produce tabby patterns in cat embryonic skin cells had activated before cats' fur began to develop. Under the microscope, these early skin cells can even be seen mimicking tabby stripes, an unprecedented discovery on embryonic cells.

This unique genetic process may be the same as the mechanism of the occurrence of markings and origins in wild cats, the authors inferred. The word "tag" in English is tabby, derived from al-'Attābiyya, which is a region of Baghdad. The area once produced striped silk taffeta in the 16th century, but the tabby stripes themselves may have originated from the direct ancestor of domestic cats, the striped Near Eastern wildcat.

"To learn more about the world, it will make people feel accomplished." Research host Greg Barsh, a researcher at the Hudson Alpha Institute for Biotechnology, a research institute based in Hencivi, Alabama. However, this study is also surprising on another level. He said: "Biology has repeatedly used the same set of tools, so it is very rare to find something that has not been widely used in many other situations. This is likely to be the case." The genetics behind the fur color and pattern of domestic cats have been shaking scientists' curiosity for a long time. Darwin once suggested that most deaf cats are white cats with blue eyes. He said that during development, species sometimes undergo small, unimportant changes, such as coat color, because these changes are linked to other more useful changes.

He added that some changes are simply invisible to us. He has no modern genetics knowledge, but he is right: this is inherited genetic abnormality.

Different types of cat cells

Because of ethical recognition of research agreements, Barsh, Stanford University geneticist Christopher Kaelin, and Hudson Alfa senior scientist Kelly McGowan collected nearly 1,000 embryos that would have been thrown away from veterinary clinics that helped street cats; many were pregnant when they were sent to the clinic.

When McGowen used a microscope to examine embryonic skin cells aged 25-28 days, she noticed that thin areas were interspersed in thicker skin, resulting in a temporary fur-color pattern, which looked like the tabby color on a cat.

What she was most surprised was that she could see such patterns in such an early stage of embryonic development; hair follicles and pigments would not appear long before they appeared, and these two were the key to the color of animal fur.

For more in-depth research, the team analyzed individual skin cells of the embryo and found two different types of cells, each showing different groups of genes. Among these genes, the most different one is the gene specifically named "Dickkopf WNT Signaling Pathway Inhibitor", which is DKK4.

They examined embryos about 20 days old to see how the cells showed DKK4, and found that the cells involved were all those that would form thicker skin lines in a few days.

Balsh explained that DKK4 is also a communication protein, known as a "secreted molecule", which sends signals to surrounding cells, basically saying: "You are special. You are the area where black hair grows."

When everything develops according to the plan, cells with the DKK4 gene will eventually become dark lines that make tabby cats have tabby. But mutations also often occur, causing other fur colors and patterns, such as white spots or finer stripes. Pigmentation can also cause other conditions: for example, all-black fur is caused when pigment cells that are to produce other colors only produce melanin.

Naturally occurring pattern development

In order to understand how these cells create pattern patterns on cats, the team turned to Alan Turing, a computer scientist and the founder of mathematical biology. In 1952, Turing once described a way to explain how patterns emerge naturally using mathematics..

His theory is called "reaction-diffusion". The prediction of this theory is that during embryonic development, when molecules such as inhibitors and activation factors (genes in the cat's case) move from cells to cells at different rates (that is, diffusion), the system can organize itself. So when the inhibitor spreads further or faster than the activation factor, then mathematically, this system can also organize itself. In the case of tabby cats, the inhibitor is the DKK4 gene, but the activation factor is unknown.

Turing did not know what the activation factor or inhibitor would be; he did not even know that there were these two things. But 70 years later, the discovery found in the tabby cat is one of the many discoveries that Turing is right.

"We always think that cells move during development, but they can determine the distribution of marks in this three-dimensional way at such an early stage with skin thickness... that's really amazing." Elaine Ostrander, who studies the inheritance of domestic dogs at the National Human Genome Research Institute in Beshstad, Maryland.

Ostende, who was not involved in the study, added that simply analyzing these cells "allows them to disassemble some of these different processes, and all of this is important to finally obtain patterns that appear in children's storybooks."

Barsh's team now believes that the production of cat colored markings is a two-stage process. First, skin cells will determine if the tabby stripes are dark or light, then hair follicles grow and pigment create.

By studying how these processes work in other animals—why some have stripes and some do not—the team hopes to unravel how the colored markings evolve. Barsh said they might also accidentally find discoveries that seem to have nothing to do with fur marks—like the invisible difference Darwin imagined before.