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House tiger: How tabby cats get their coat pattern

House cats : Like cats you do Get a fur pattern

A gene called »Dickkopf & nbsp; 4« creates the stripes in the cat's fur. They develop long before the first hair follicles form. by Lars Fischer Two baby cats are lying in a basket and look expectantly into the camera. © w-ings/Getty Images/iStock (excerpt)

The different colored fur patterns of tabby cats develop in the early embryo, long before the hair follicles form. Thickened and thinner zones are formed on the skin of the embryo, which correspond to the later darker and lighter areas, reports a working group led by Gregory S. Barsh from Stanford University. As the team in & raquo; Nature Communications & laquo; writes, it identified the “Dickkopf & nbsp; 4” (DKK4) gene, which encodes a signaling molecule, as a central factor in this pattern formation. In its study, it used cat embryos that are produced in veterinary clinics when neutering cats that have gone wild. The researchers used these to examine the structure of the skin and the activity of various genes at different stages of development. In doing so, the team came across a mutation of DKK4, which ensures that an actually tabby cat loses its coat pattern and appears monochrome. The study sheds light on another aspect of the formation of fur patterns in mammals, which remains a mystery to this day.

The hair follicles in mammals arise from identical cells of the skin layer of the embryo. But in order to create the different patterns of the tabby cats, the resulting hair must have different colors depending on the region. Experts suspect that this is due to chemical feedback loops that either strongly express or completely suppress certain signals, depending on their immediate environment. The basic mechanism was already described in 1952 by the British mathematician Alan Turing & nbsp; & # 8211; How the process works and is controlled in reality has only been partially clarified.

In tabby cats, with their light and dark stripes, some details of this patterning process are known. Barsh's team took advantage of one of them. It is known that the original tiger stripes turn into a marble cake-like pattern if the gene for the protein transmembrane aminopeptidase & nbsp; Q (Taqpep) is defective. Based on this peculiarity, the team showed that the thickened areas in the skin of the cat embryos actually correspond to the later dark tiger stripes. With further genetic analyzes it then demonstrated that the activity of DKK4 creates this striped pattern even before the thick and thin zones develop.

The gene »Dickkopf & nbsp; 4« & nbsp; & # 8211; unlike the name suggests, this gene family was not discovered in cats, but in clawed frogs & nbsp; & # 8211; is therefore right at the beginning of the striping of tabby cats. It codes for a protein that interferes with cell signaling pathways. In the further course of the stripe development, the formation of the DKK4 protein shifts more and more to individual cells of the stripe region & nbsp; & # 8211; until it only appears in those cells that later form dark hair. The working group discovered another indication of the meaning of “Dickkopf & nbsp; 4” in a mutation of this gene. If it is unusable due to a change, the cat is not mackerel but “ticked”. Such cats have the facial markings of tabby cats, but no coat pattern. Their fur only appears lighter or darker in some places because the individual hair is striped.

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