Explained: How the cats got their stripes and spots?

Over the years, we have heard a million theories on how tigers and other members of the family such as cats got their stripes and spots but little scientific evidence was available to support them. 

However, the scientists' fraternity that was long intrigued by the stripes and spots on domestic cats have now discovered a gene that is responsible for the said patterns.

What does the research say?

A study recently published in Nature Communications journal revealed that a specific gene in domestic cats plays a key role in determining the pattern they are going to have on their coats. 

It further underscored that the pattern can be predicted in the embryonic stage, long before hair follicles develop and assume their distinctive colours.

The team of researchers associated with the HudsonAlpha Institute for Biotechnology in Alabama and the Stanford University School of Medicine include Greg Barsh, Christopher B. Kaelin and Kelly A. McGowan. 

Gene responsible for the patterns on cats

Dickkopf4 gene, also known as the Dkk4 gene, plays a major role in setting off a reaction between two chemicals and determine the pattern of a cat's fur. One of these chemicals stimulates genetic activity, while the other inhibits it, leading to the formation of dark and light stripes on your cat.

How the research was carried out?

Hundreds of embryos that would otherwise have been discarded were collected by the researchers from veterinary clinics that sterilize feral cats by removing the ovaries, many of which were pregnant when admitted. 

The senior scientist, McGowan examined the skin cells of embryos that were 25-28 days old under the microscope. She noticed thicker areas of skin were interspersed with thinner areas, creating a temporary colour pattern that resembled the tabby colouring of an adult cat.

The team further analyzed embryos’ individual skin cells and found that each of them expressed separate sets of genes. Among these, the DKK4 gene differed the most. 

DKK4 is a messenger protein that signals cells surrounding it to become dark. However, mutations often occur leading to white spots or thinner stripes. Further, pigmentation alterations can also occur such as an all-black coat-- when the pigment cells produced only dark pigment. 

Basis of research

The theoretical basis of the study is based on British scientist Alan Turing's work on mathematical biology in 1952. Truing predicted a reaction-diffusion process where two chemicals, one that stimulates gene activity and one that inhibits it, can result in regular, alternating patterns. In the case of cats, DKK4 is the inhibitor but the activator is unknown. 

Charles Darwin proposed that most deaf cats were white with blue eyes. He stated that during the development process, species acquire inconsequential changes such as hair colour because they were linked to other, more useful changes. The succeeding research will uncover how tissue patterns change to different colours when the hair follicles start developing in kittens.

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