Uniparental chromosome elimination in the early embryogenesis of the inviable salmonid hybrids between masu salmon female and rainbow trout male |
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Authors: | Atushi Fujiwara Syuiti Abe Etsuro Yamaha Fumio Yamazaki Michihiro C Yoshida |
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Institution: | (1) Laboratory of Cytogenetics, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060, Japan, JP;(2) Chromosome Research Unit, Faculty of Science, Hokkaido University, North 10, West 8, Kita-ku, Sapporo 060, Japan, JP;(3) Nanae Fish Culture Experimental Station, Faculty of Fisheries, Hokkaido University, Kameda 041-11, Japan, JP;(4) Laboratory of Breeding Science, Faculty of Fisheries, Hokkaido University, Hakodate 041, Japan, JP |
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Abstract: | Chromosome elimination through chromosome loss and partial deletion is known to be one of the causes of embryonic inviability
in some salmonid interspecific hybrids. Using fluorescence in situ hybridization and related techniques, including whole chromosome
painting and comparative genomic hybridization, parental origin of eliminated chromosomes was identified in the inviable hybrids
between masu salmon (Ms, Oncorhynchus masou) female and rainbow trout (Rb, O. mykiss) male at the early embryonic stage prior to death. In these hybrids, the haploid Rb chromosome number decreased to nearly
half, whereas the Ms chromosomes were retained as one or occasionally two full haploid complements. The Rb chromosomes were
also involved in the frequently observed fragments and micronuclei. Whereas the occurrence of fragments was constant throughout
the observed period, chromosome loss occurred mainly from just after fertilization to the blastulae stage. In tissue sections
and cell spreads of late blastula, some Rb chromosomes were trapped in the midzone from ana- to telophase, resulting in micronuclei
at the subsequent interphase. Micronuclei and mitotic abnormalities were also observed in the androgenetic haploid hybrids.
However, such abnormalities were seldom or never observed in the viable reciprocal hybrids. The present findings suggest that
the paternal Rb chromosomes in the inviable hybrids are preferentially eliminated through mitotic abnormalities during early
embryogenesis, owing to a possible incompatibility between the maternal Ms cytoplasm and paternal Rb genome.
Received: 22 August 1996; in revised form: 14 November 1996 / Accepted: 20 November 1996 |
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