Agouti gene

As agouti (also tabby or agouti ) is called the classic coat pattern of domestic cats, but also coat patterns of other species such as degus, rabbits, rats, mice or guinea pigs. The corresponding gene locus is named after the agoutis, South American rodents, which show a typical expression of wild color.

Functioning of the gene

Agoutilocus of (a) the gene for the agouti signaling peptides (ASIP ), whose function will be simultaneously affected by the melanocortin receptor 1 ( MC1R ), the extension of the locus (S) is encrypted.

About the agouti gene, the pigment cells are influenced by their location and the surrounding cellular milieu and the distribution of black and yellow pigments controlled. This results in both the light and dark banding of individual hairs of the wild coloration of many animal species as well as the distribution over the whole body, such as in the saddle expression of the German Shepherd.

Mutations of this locus is the yellow band of the single hair either lost ( non-agouti ) or expands ( or yellow agouti ). The ventral side of the body for the Phäomelaninbildung is preferred. Alleles of this locus be abbreviated to A, where the dominant allele A, the yellow and the recessive allele a, the black hair color coded.

That is, by mutations of the Agoutilocus the black areas can be magnified in the coat pattern ( Nigrismus ) to, in extreme cases, the entire body is black ( Skotasmus ); The result is thus " melanism " to varying degrees. By Agoutilocus induced melanism is a recessive trait.

Conversely, dark fur drawings can be reduced until they disappear completely in extreme cases and the animal fox red over the entire body or yellow. Some mutations of this locus lead to obesity and yellow fur, partly associated with diabetes mellitus.

Dog

At the house the dog Agoutilocus located on chromosome CFA24.

There are four alleles. The allele fawn / sable (ay ) leads to sand-colored, yellow, or red-brown animals that sometimes have a dark face mask, a semi- drawing from dyed black hair like the Collie or individual dark hair in the coat. The allele aw ( wolf sable ) is the allele of the wild -colored dog with lots of light and dark banded hair. The allele at (black - and-tan or brown- and-tan ) leads to a black dog with lighter markings on the legs and face. The recessive allele for a completely black color occurs at the German Shepherd Dog ( Groenendael, as well as, Schipperke, Shetland Sheepdog, and Newfoundland ). However, there is another gene which leads to a dominant color, and black K is encoded by the locus. It is assumed that the order of the dominant gene for rezessivsten looks like this: ay > aw > at > a

Mouse

When breeding form of the house mouse, there are several alleles that produce coloration variants, ranging from dominant to recessive bright color to black color.

A specific mutation of this gene locus is called Viable Yellow. In homozygous animals, this mutation is associated with " yellow " color, fatty degeneration, increased propensity for cancer and increased insulin secretion.

Hybrids that have one of the agouti gene is an allele for black color and for Viable Yellow, can be just as "yellow" look like a mouse in which both alleles of the Agouti have locus the Viable - Yellow variant. But you can also look like the parent animal in which both alleles code for the color black mice; Moreover, there are black and yellow spotted mice. By imprinting, - that the switching off of an allele of the agouti gene in each cell by the DNA is methylated before these genes - determines which of the alleles of the gene in each hair as it is active and visible on the basis of the resulting color.

If now mice fed with food, which makes it easier to the mice to methylate one of the alleles new, so that it can no longer be active, the non-mutated gene is active than in mice that do not receive this common feed. In addition, plays a role in whether the gene in the mother was more active or inactivated; Mice can thus inherit not only their genes but also their activation state. In addition, the allele comes from the mother, often active, than that which comes from the father.

Cats

In cats is agouti (A) the wild-type and dominant. The agouti gene causes the tabby pattern is formed.

The mutation Nonagouti ( a) is recessive. A cat with the genotype aa is monochromatic, if it is not red or cream. The Nonagouti allele causes the hair is not banded, but are colored monochrome. Only in young animals the tabby pattern seems nor as a ghost markings.

Horse

In the horse, the dominant agouti gene A corresponds to the coat color of the brown (brown with black mane and black tail ) incurred while the recessive form ( a) results in that the Black spread all over the body and a black horse.