These mice are heterozygous for two different alleles of oculocutaneous albinism II (Oca2): Oca2p-d (dark pink-eye) and Oca2p-25H (pink-eyed dilution 25 Harwell). The compound heterozygotes have a color phenotype intermediate between those of the two homozygotes with eyes lighter at birth than those of Oca2p-d mice, but not as light as those of Oca2p mice, and darken by weaning.Read More +
Oca2p-25H/Oca2p-25H mice exhibit significant dilution of coat color with pink eyes, similar in appearance to Oca2p/Oca2p mice. The Oca2p-25H phenotype also includes a slightly jerky gait with some tremor, small body size compared to control littermates, male sterility, female semisterility, and impaired maternal behavior, and the smaller-than-expected proportion of Oca2p-25H homozygous intercross offspring implies reduced prenatal viability (Lyon et al. 1992, Phillips et al. 1977). The Oca2p-25H mutation comprises an inversion of a segment of Chromsome 7 that alters the 5' end of the Oca2p gene so that no detectable ptranscript is produced, accounting for the pigment-dilution phenotype (Gardner et al. 1992). The deletion also disrupts the Herc2/rjs gene proximal to Oca2p so the transcript sequence diverges from wild-type after the first 8772 bp (of 15 kb in wild-type), resulting in a truncated protein and accounting for the non-pigment related aspects of the Oca2p-25H phenotype (Lehman et al. 1998). Mice homozygous for Oca2p-d are born with lightly pigmented eyes, darker than those of Oca2p/Oca2p mice, which darken by weaning and a coat color "considerably darkerthan that of Oca2p/Oca2p mice, somewhat resembling that of brown [Tyrp1b/Tyrp1b] mice"; both sexes are fertile (Gardner et al. 1977, Lyon et al. 1992). A normal-sized Oca2p transcript is present in eyes of Oca2p-d/Oca2p-d mice (Gardner et al. 1992), and Southern blot analysis revealed no gross alteration of the Oca2p gene (Gardner et al. 1992, Lyon et al. 1992); thus, the molecular nature of the defect is unknown. Oca2p-d/Oca2p-25H compound heterozygotes have a color phenotype intermediate between those of the two homozygotes: eyes are "lighter at birth than those of Oca2p-d/Oca2p-d mice (but not as light as those of Oca2p/Oca2p mice) and darken by weaning"; ears and tail are lighter than those of Oca2p-d/Oca2p-d mice, but coat color is indistinguishable. The compound heterozygotes exhibit no behavioral abnormalities and are fertile (Lyon et al. 1992).
Both the Oca2p-d and Oca2p-25H mutations were radiation induced at the Medical Research Council Radiobiology Unit, Harwell, UK, the former by X-irradiation of the fetus and the latter by neutron irradiation of a male mouse, both of strains/stocks of unidentified lineage.
|Allele Name||pink-eyed dilution 25 Harwell|
|Allele Type||Radiation induced|
|Allele Synonym(s)||Herc2p-25H; p25H|
|Gene Symbol and Name||Oca2, oculocutaneous albinism II|
|Strain of Origin||Not Specified|
|General Note||p25H, p-25 Harwell, recessive. This allele was neutron-irradiation-induced. Homozygotes are very similar to p6H homozygotes, except that sperm morphology differs; p25H homozygous males have a lower proportion of normal sperm (J:5219, J:5501, J:15082, J:5808). The sperm shows a loss of negative charge along the whole length of the tail (defined by the inability to stain with the positively charged colloidal iron hydroxide), suggesting that the defect in spermatogenesis may involve the Golgi apparatus and/or plasma membrane (J:11957). Females have reduced fertility. In addition, in p25H homozygotes of both sexes, the pars nervosa of the pituitary contains degenerating nerve axons (J:5508), and the hypothalamus has reduced binding capacity for estradiol-17ÃŸ (J:5219). Mutant females can generally produce a small, first litter, but the pups often die neonatally due to poor maternal behavior, which may involve improper nesting (J:49046).|
|Molecular Note||Southern blot analyses using cDNA probes from the pink-eyed dilution locus show that this allele comprises an inversion of a segment of Chromsome 7 that alters the 5'end of the Oca2p gene preventing transcription of p.|
The male sterility, female semisterility and failure of females to nurture their young that are characteristic of Oca2p-25H homozygotes necessitate maintaining this mutation by mating compound heterozygotes. Oca2p-25H/Oca2p-25H females may produce one or two litters, but the pups must be fostered to survive.
When using the STOCK Oca2p-d/Oca2p-25H/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #001585 in your Materials and Methods section.