Genetic mapping of the dominant albino locus in rainbow trout ( Oncorhynchus mykiss )
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O R I GI N A L P A P E R
K. Nakamura á A. Ozaki á T. Akutsu á K. Iwai T. Sakamoto á G. Yoshizaki á N. Okamoto
Genetic mapping of the dominant albino locus in rainbow trout (Oncorhynchus mykiss ) Received: 25 November 2000 / Accepted: 24 January 2001 / Published online: 25 April 2001 Ó Springer-Verlag 2001
Abstract Albinism in animals is generally a recessive trait, but in Japan a dominant oculocutaneous albino (OCA) mutant strain has been isolated in rainbow trout (Oncorhyncus mykiss). After con®rming that this trait is not due to a tyrosinase gene mutation that causes OCA1 (tyrosinase-negative OCA), we combined the ampli®ed fragment length polymorphism (AFLP) technique with bulked segregant analysis (BSA) to map the gene involved in dominant oculocutaneous albinism. Four AFLP markers tightly linked to the dominant albino locus were identi®ed. One of these markers was codominant and we have it converted into a GGAGTrepeat microsatellite marker, OmyD-AlbnTUF. Using this pentanucleotide-repeat DNA marker, the dominant albino locus has been mapped on linkage group G of a reference linkage map of rainbow trout. The markers identi®ed here will facilitate cloning of the dominant albino gene in rainbow trout and contribute to a better understanding of tyrosinase-negative OCA in animals. Keywords Dominant albino locus á Rainbow trout á Tyrosinase locus á AFLP marker á Microsatellite marker
Introduction Oculocutaneous albinism (OCA) is the most commonly inherited disorder of generalized hypopigmentation. As Communicated by G. P. Georgiev K. Nakamura á A. Ozaki á K. Iwai á T. Sakamoto G. Yoshizaki á N. Okamoto (&) Department of Aquatic Biosciences, Tokyo University of Fisheries, Konan 4, Minato-ku, Tokyo 108-8477, Japan E-mail: nokamoto@tokyo-u-®sh.ac.jp Fax: +81-3-5463-0552 T. Akutsu Fuji Trout Hatchery, Shizuoka Prefecture Fisheries Experimental Station, Fujinomiya, Shizuoka 418-0108, Japan
the techniques of molecular biology have developed, our knowledge of pigmentation at the molecular level has rapidly increased. Over the past several years, King et al. (1995) have classi®ed human albinism in terms of the genes responsible for the condition. OCA1 is caused by mutations in the tyrosinase gene (TYR), and includes the non-pigmenting type OCA1A, and the pigmenting types OCA1B (yellow OCA), OCA1MP (minimal pigment OCA) and OCA1TS (temperature-sensitive OCA). OCA2 refers to phenotypes caused by mutations at the P gene locus. Brown OCA (BOCA) and Rufous OCA (ROCA) were recently classi®ed as OCA3, and are caused by mutations in the gene for tyrosinase-related protein-1 (TRP-1) (Boissy et al. 1996; Manga et al. 1997). Autosomal dominant OCA has been described in several families (Bergsma and Kaiser-Kupfer 1974; Fitzpatrick et al. 1974; Frenk and Calame 1977), but remains unclassi®ed. The characterization of this form was incomplete and most cases did not ®t the criteria for albinism (King et al. 1995). Final characterization of dominant OCA awaits the careful evaluation of families with clear autosomal dominant expression of
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