Genetic mapping of the dominant albino locus in rainbow trout (Oncorhynchus mykiss)

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 confirming that this trait is not due to a tyrosinase gene mutation that causes OCA1 (tyrosinase-negative OCA), we combined the amplified 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 identified. One of these markers was codominant and we have it converted into a GGAGT-repeat 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 identified here will facilitate cloning of the dominant albino gene in rainbow trout and contribute to a better understanding of tyrosinase-negative OCA in animals.

Generation of a white-albino phenotype from cobalt blue and yellow-albino rainbow trout (Oncorhynchus mykiss): Inheritance pattern and chromatophores analysis

“…Color variations from wild-type have been described for many teleosts, especially in farmed species subjected to intensive inbreeding [25]. In rainbow trout, color phenotypes including the yellow-albino and cobalt/metallic blue have been reported, but most of them display recessive inheritance and impairments related to growth or reproduction aspects [12,14]. In this Fig 2A).…”

“…The inheritance of albino phenotypes is determined mainly by recessive genes [11], but there is also a case of a dominant strain [14]. In case of blue phenotype, Blanc and collaborators [15] described a blue strain with autosomal, recessive inheritance.…”

A second generation genetic map for rainbow trout (Oncorhynchus mykiss)

“…An evolutionarily recent whole genome duplication event is estimated to have occurred 25–100 mya [ 45 ], and the genome is estimated to be 1/3 of the way along the process of re-diploidization, [ 46 ]. Several laboratories have constructed genetic maps including AFLPs, microsatellites, and SNPs to identify quantitative trait loci (QTL) affecting time to hatch, development rate, growth, thermal tolerance, natural killer cell-like activity, albinism and disease resistance [ 47 - 56 ]. The first genetic map based on molecular markers was constructed by Young et al .…”

Estimates of linkage disequilibrium and effective population size in rainbow trout

“…To this end several international laboratories have produced genetic maps for this species to aid in the identification of loci affecting phenotypes of interest. These maps primarily include amplified fragment length polymorphisms (AFLPs) and microsatellites [3-9] and have resulted in the identification of many quantitative/qualitative trait loci (QTL) affecting phenotypic variation in traits associated with albinism, disease resistance, temperature tolerance, sex determination, embryonic development rate, spawning date, condition factor and growth [10-19]. In spite of these efforts, the elucidation of the precise allelic variations and/or genes underlying phenotypic diversity has yet to be achieved in this species having low marker densities and lacking a whole genome reference sequence.…”