Patterns of Fur

During developement of embryo, cells which will be melanocytes (melanoblasts) migrate from dorsal area - from active region, which is place alongside of back of embryo and is called neural crest - to whole body. These cells will become basics of hair follicles and also pieces of organs like eye, inner ear and nervous system. If migration of melanocytes is for some reason disrupted, some parts of the body will not have any melanocytes and in these areas will be produced white fur.

Pigmentation cells usually migrate to some specific places. Three are on the head (close to eyes, ears and on the top of the head), six on the side of the body and some around the tail. They multiply at those places and migrate to next parts where they connect into bigger fields. They spread down to paws and from head area down where they connect at the chin and down the body where they meet on the belly. Pigmentation cells also migrate into iris and eye retina. If iris has no pigmentation, it looks like red (hamsters, rats and mice) or blue (dogs and cats). Odd eyes are consequence of migration of pigmentation only into one eye. Pigmentation cells also migrate to inner ear where they affect hearing. If inner ear has not enough of pigmentation cells, animal can be deaf. They also migrate to the brain where lack of them can lead to motion troubles or affect changes in behavior. From crest area migrate except for pigmentation cells also nerve cells and if necessary amount of them doesn´t reach guts it might happen that they don´t function good enough and animal is not able to secrete and that leads to illness called megacolon. So that happens quite often that pattern of fur, abnormality of eye colour, deafness and megacolon can be seen together. All these troubles are consequence of delay of migration of melanocytes from neural crest.

Mutations occur in distribution of melanocytes:

Mutations in endothelin B receptor creates spotted pattern. Normal migration of cells melanocytes and neural cells is dependent on present of endothelin B and its receptors, which regulates their dividing, spreading and migration. Gene which affects function of endothelin B receptor causes depigmentation on the forehead and further around the body. .

Mutation in kit protein causes that kit protein, which is produced by c-kit gene, is partially damaged. Mutation causes that there are missing 12 bases in c-kit gene. Kit protein has more functions, except of normal distribution of pigment cells also affects distribution of neural cells. Result of this is white spotting.

In Syrian hamster exists these assumptions about origin of patterns of fur: Dominant Spot (Dsds) could be kit protein mutation, Piebald (ss) as well; Banded pattern (Ba_) is probably not kit protein mutation but originates in mistake in early migration of cells from spine area; White Bellied/Roan (Whwh) could be result of apoptosis, what is actually cell suiside and it is mechanism used to eliminate redundant or damaged cells, it is cell eclipse caused by activation of cystein protease caspases and afterwards nuclear endonukleases and Recessive Dappled (rdrd) could be combination of both last named.

If hamster has more patterns of fur, patterns make synergistic action and resulting white areas are bigger then they would be each alone and summarized.