Molecular mechanisms of gynogenetic clonal reproduction in polyploid crucian carp

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This three-year project was to study the molecular mechanisms underlying gynogenesis practiced by a population, or subspecies, of Japanese crucian carp, namely, Carassius auratus langsdorfi. This extremely rare and interesting vertebtare(fish) has been known to produce unreduced eggs with its genomic constitution exactly identical to that of somatic cells by means of 1. skipping the first meiotic division and 2. upon insemination, keeping the membrane of incoming sperm nucleus undamaged, thus prohibiting the male genome from participating in embryo development. Such a type of clonal reprodction as this one is remarkable in terms of both basic developmental biology and developing an artificial way of mass production of clonal offspring.In this study, we examined a sizable collection of C.a.langsdorfi (both the bisexsual diploid and all-female tri- or tetraploid) and several other C.a. subspecies, including the goldfish, from many parts of Japan for their mitochondrial D-loop sequences, DNA markers which we found specific/polymorphic, electrophoretograms of RAPD-PCR with carefully selected primers, and we almsot surely clarified the maternal origin of the genomes of the gynogenetic populations. In the course of this investigation, a strong link between the triploid genome and genomes of both diploid C.a. and goldfish was also found.In search for genes that are related to gynogenetic mechanisms, we chose two approaches : close examination of wee1 gene, an important cell-cycle regulating gene, and mutual subtraction of cDNAs from overies of both diploid and triploid fish. For the former, we conducted a thorough characterization of wee1 gene and its product. For the latter, four genes were isolated which were reasonably expected to be related to the gynogenetic phenomena and they were analyzed for the base sequences and patterns of expression.