PubMed · 13077676
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H F FALLS. Albinism.. https://pubmed.ncbi.nlm.nih.gov/13077676/
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Albino animals display a hypopigmented phenotype associated with several visual abnormalities, including rod photoreceptor cell deficits, abnormal patterns of connections between the eye and the brain and a general underdevelopment of central retina. Oculocutaneous albinism type I, a common form of albinism, is caused by mutations in the tyrosinase gene. In mice, the albino phenotype can be corrected by functional tyrosinase transgenes. Tyrosinase transgenic animals not only show normal pigmentation but the correction of all visual abnormalities associated with albinism, confirming a role of tyrosinase, a key enzyme in melanin biosynthesis, in normal retinal development. Here, we will discuss recent work carried out with new tyrosinase transgenic mouse models, to further analyse the role of tyrosinase in retinal development. We will first report a transgenic model with inducible tyrosinase expression that has been used to address the regulated activation of this gene and its associated effects on the development of the visual system. Second, we will comment on an interesting yeast artificial chromosome (YAC)-tyrosinase transgene, lacking important regulatory elements, that has highlighted the significance of local interactions between the retinal pigment epithelium (RPE) and developing neural retina.
We identified the rat pink-eyed dilution (p) and pink eye Mishima (p(m)) mutations. The p(m) mutation, which was isolated from a wild rat caught in Mishima Japan in 1961 and is carried in the NIG-III strain, is a splice donor site mutation in intron 5. The p mutation, which was first described in 1914 and is carried in several p/p rats including the RCS and BDV strains, is an intragenic deletion including exons 17 and 18. In addition to RCS and BDV strains, several albino strains, KHR, KMI and WNA, all descendants of albino stock of the Wistar Institute, are homozygous for the p allele. Analyses revealed that the colored p strains and the Wistar-derived albino p strains had the same marker haplotype spanning approximately 4 Mb around the P locus. This indicates that these p strains share a common ancestor and the p allele did not arise independently via recurrent mutations. The historical relationship among the p strains suggests that the p deletion had been maintained in stock heterogeneous for the C and P loci and then was inherited independently by the ancestor of the Wistar albino stock and the ancestor of the pink-eyed agouti rats in Europe.
Maternal effects can form an important source of variation in offspring fitness and have important evolutionary and ecological consequences. To explore genetic control for body size of newborn offspring, the present study examined maternal brood size and offspring body size in 14 strains and performed cross experiments in an ovoviviparous fish, guppy. Correlation analyses among the strains indicated that the strains with larger brood size have smaller offspring body size. Diallel and reciprocal crosses among four strains revealed a large maternal, but no paternal, contribution to offspring body size. To examine whether offspring body size is determined by maternal genotypes and whether offspring body size correlates with albinism, backcrosses were performed between a wild-type strain with large offspring body size and an albino strain. Offspring body size differed from both the parental strains in one generation of backcrossing but was not significantly different from the paternal strains after three generations. In the backcross generations, the offspring yielded by albino individuals showed significantly smaller body size than those yielded by normal individuals. These results indicated that offspring body size is determined by maternal genotypes, suggesting that offspring body size is influenced by the maternal albinism gene or the maternal locus linked with the albinism locus. The significant negative correlation between maternal brood size and offspring body size detected through our experiments showed that the maternal genetic character of brood size strongly correlated with offspring body size, indicating genetic trade-off between maternal brood size and offspring body size in the guppy.