Pink-eyed dilution gene

Young mice exhibiting the pink-eyed dilution gene (MisterMiceGuy 2019).

The first documented version of the pink-eyed dilution mutation is believed to come from Asia and today there are over 100 documented varieties. Some of them occurred due to spontaneous natural mutations while others were induced mutations by means of x-ray or chemical mutagens. The genes occur on chromosome 7 and its referred to as the P-locus (Brilliant, Ching, Nakatsu, and Eicher 1994). The version of P-locus gene that is present in the fancy mouse hobby is simply called “Pink-Eye Dilution” (p). This is reported to be the oldest and most common version of the gene (Silvers 1979).

A common feature among these P-locus genes is a reduction in coat color and eye color pigment. Depending on the version of the gene this effect can be minor or extreme. Although the pink-eye effect can appear similar to that of C-locus genes, such as albino or siamese, but the genes are different and occur at a different locus (The Finnish Mouse Club 2020, Brilliant, Ching, Nakatsu, and Eicher 1994).

The genotype for homozygous pink eye is “p/p” but this is always combined with other coat color genes and produces a variety of phenotypes (American Fancy Rat and Mouse Association 2019).

MisterMiceGuy’s original Pink-eyed Mouse (MisterMiceGuy 2019).

Another thing to keep in mind that different Fancy Mouse Clubs may use different terms to describe a phenotype even though the genotype may be the same. For example mice that have the pink-eyed black genotype (aa pp) may be referred to as Dove, Lilac (The Finnish Mouse Club 2020) or blue lilac (Silvers 1979). Conversely, sometimes a phenotype name may be used regardless of the mouses genotype (Fance Mouse Breeders Association 2020).

Some common phenotype names that involve the pink-eye dilution gene include Dove, Pink-eyed Dove, Lilac, Blue Lilac, Silver, Pink-eyed Blue, champagne, Cream, Chinchillated Dove, Lavender, Orange, Argente, Blue Argente, Argnete Creme, Pink-eyed Fawn, Cinnamon, Fawn, or White. Pink-Eye Dilution gene can also accompany any variety of marking such as pied, spashed, broken, hereford, head spot, rumpwhite, merle, roan or any variety of coat type such as nude, angora, texel, or frizzie (Fance Mouse Breeders Association 2020, Silvers 1979, The Finnish Mouse Club 2020, American Fancy Rat and Mouse Association 2019).


Brilliant, M., Ching, A., Nakatsu, Y, and Eicher, E. (1994) The Original Pink-Eyed Dilution Mutation (p ) Arose in Asiatic Mice: Implications for the H4 Minor Histocompatibility Antigen, Myodl Regulation and the Origin of Inbred Strains. Genetics, 138, 203-211

Silvers, W. (1979) The Coat Colors of Mice: A Model for Mammalian Gene Action and Interaction. Springer Verlag, Retrieved from:

American Fancy Rat and Mouse Association (2019) Fancy Mouse Genes, Alphabetical Name Listing, Retireved from:

The Finnish Mouse Club (2020) P-locus. Retrieved from:

Fancy Mouse Breeder’s Association (2020) Show Standards. Retrieved from:

The Long Hair Genes

Pied Recessive Yellow mouse with long hair (Photo Credit: MisterMiceGuy)

MisterMiceGuy has always been enamored with long haired animals and mice are no exception. In fact is seems that long haired mice are very popular among pet owners and hobby breeders in general (The Finnish Mouse Club 2020). Because of this MisterMiceGuy is incorporating long haired genes into his line of mice.

Illustration of the hair growth cycle in humans. FGF5 protein reduces time spent in the anagen phase and decreases hair length (Photo Credit: Capillus 2017)

There may actually be many genes influencing the length of a mouse’s coat (The Finnish Mouse Club 2020). The gene at play for hobbyist mice seems to be mutations of Fibroblast growth factor 5 gene (FGF5)(The Finnish Mouse Club 2020, Hébert, Rosenquist, Götz, and Marin 1994). Fibroblast Growth Factor 5 (Fgf5) is found on the outer root sheath of hair follicles during the anagen VI phase, which is a phase of hair follicle growth. The FGF5 protein serves to inhibits the elongation of the hair shaft and induces that start of the catagen phase of the hair cycle (Hébert, Rosenquist, Götz, and Marin 1994, and Ota et al. 2002) . In fgf5neo this growth factor seems to be reduced allowing for increased hair length (Hébert, Rosenquist, Götz, and Marin 1994).

According to The Finnish Mouse Club (2020) there is also the Angora gene (go) which appears to be present in the hobby population. Phenotypically it is similar or identical to fgf5neo. Unfortunately as it turns out angora is also recessive a mutant of the FGF5 gene meaning that mice with fgf5neo and fgf5go do not result in augmented hair length when bred together (Hébert, Rosenquist, Götz, and Marin 1994).

It appears that there may be other long hair genes that either are not common or do not exist at all in the hobby population and some of these include, lgh, Fgf5tm1Mrt, skc6, and skc8 genes (The Finnish Mouse Club 2020)

Based personal experience MisterMiceGuy suspects that there are even more additional factors affecting coat length. In mice, coat length reduces with age which may indicate an increased production of FGF5 protein with age. Additionally it seems that there is some difference between guard hairs and undercoat as some mice have very long guard hairs but an average undercoat. Anothing thing that MisterMiceGuy has noticed is that there are differences between hair density which seems unrelated to hair length but effects the overall appearance of the mouse’s coat.


Capillus (2017) Understanding Hair Growth Stages. Retrieved from:

Hébert, J., Rosenquist, T., Götz, J., and Marin, G. (1994) FGF5 as a regulator of the hair growth cycle: Evidence from targeted and spontaneous mutations. Cell, (78)6, 1017-1025.

The Finnish Mouse Club (2020) Varieties. Retrieved from:

Ota, Y., Saitoh, Y., Suzuki, S., Ozawa, K., Kawano, M., and Imamura, T. (2002). Fibroblast growth factor 5 inhibits hair growth by blocking dermal papilla cell activation. Biochemical and Biophysical Research Communications. 290(1), 169-76.