Development of a novel pink-eyed dilution mouse model showing progressive
darkening of the eyes and coat hair with aging |
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Authors: | Akira ISHIKAWA Makoto SUGIYAMA Eiichi HONDO Keiji KINOSHITA Yuki YAMAGISHI |
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Institution: | 1)Laboratory of Animal Genetics, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan;2)Laboratory of Animal Morphology and Function, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan;3)Present address: Laboratory of Veterinary Anatomy, School of Veterinary Medicine, Kitasato University, Higashi, Towada, Aomori 034-8628, Japan |
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Abstract: | Oca2p-cas (oculocutaneous albinism II; pink-eyed dilution
castaneus) is a coat color mutant gene on mouse chromosome 7 that arose spontaneously in
wild Mus musculus castaneus mice. Mice homozygous for
Oca2p-cas usually exhibit pink eyes and gray coat hair on
the non-agouti genetic background, and this ordinary phenotype remains unchanged
throughout life. During breeding of a mixed strain carrying this gene on the C57BL/6J
background, we discovered a novel spontaneous mutation that causes darkening of the eyes
and coat hair with aging. In this study, we developed a novel mouse model showing this
unique phenotype. Gross observations revealed that the pink eyes and gray coat hair of the
novel mutant young mice became progressively darker in color by approximately 3 months
after birth. Light and transmission-electron microscopic observations revealed a marked
increase in melanin pigmentation of coat hair shafts and choroid of the eye in the novel
mice compared to that in the ordinary mice. Sequence analysis of
Oca2p-cas revealed a 4.1-kb deletion involving exons 15
and 16 of its wild-type gene. However, there was no sequence difference between the two
types of mutant mice. Mating experiments suggested that the novel mutant phenotype was not
inherited in a simple fashion, due to incomplete penetrance. The novel spontaneous mutant
mouse is the first example of progressive hair darkening animals and is an essential
animal model for understanding of the regulation mechanisms of melanin biosynthesis with
aging. |
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Keywords: | animal model coat color hair darkening mouse Oca2 |
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