Satoshi Furukawa

Bangladesh Agricultural University, Mymensingh, Bangladesh

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Publications (10)6.51 Total impact

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    ABSTRACT: The full-length of insulin-like growth factor (IGF) complementary (c)DNAs encoded by igf-I and igf-II from torafugu pufferfish Takifugu rubripes were cloned in the present study. The deduced amino acid sequences of the two genes showed c. 80% identity each with those of Igf-I and Igf-II from other teleosts, respectively. Two growth hormone (GH) receptors, ghr1 and ghr2, were also cloned in silico using the T. rubripes Fugu genome database. The transcripts of T. rubripes igf-I were detected in slow muscle, heart, skin, gill, liver and intestine but not in fast muscle, spleen and testis of adult fish, whereas those of igf-II were found in all tissues examined. Subsequently, the accumulated messenger (m)RNA levels of igf-I and igf-II were investigated in an F(2) population derived from a male of an apparent fast-growing T. rubripes strain and a wild female T. rubripes together with those of other growth-related genes encoding Gh, Ghr1 and Ghr2, and with those of prolactin (Prl) and leptin (Lep) previously reported. The accumulated mRNA levels of igf-I, gh and ghr1 were significantly correlated to growth rate at larval stages in the population, but not for those of igf-II, prl, ghr2 and lep. Although it is unclear whether or not this phenotype is directly related to the heredity of the fast-growing strain, the findings suggest that the expression of igf-I, gh and ghr1 is involved in the regulation of growth rate at larval stages in T. rubripes.
    Journal of Fish Biology 10/2011; 79(4):854-74. · 1.83 Impact Factor
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    ABSTRACT: It has been reported that the nucleotide sequences of the mitochondrial and nuclear genes of Takifugu pufferfish torafugu T. rubripes and karasu T. chinensis show 99–100% sequence identity, indicating a very close relationship between the two species. To further investigate this genetic relationship, we compared genetic variation at four microsatellite loci and at the mitochondrial control region (CR) (561bp) between groups of T. rubripes caught at two locations [TrG, caught in the Genkai Sea off Tsushima Island in 2003 (n=50); TrS, caught in the Suwo Sea off Kita-Kyushu in 2008 (n=50)] and T. chinensis caught at one location (TcK, caught off the east coast of Korea in 2004; n=50). Analyses using microsatellite loci showed that genetic diversity index values of the TrG, TrS and TcK groups were 0.9505, 0.9350 and 0.9335, respectively, while values of genetic distance and genetic differentiation between TrG and TcK (0.0543 and 0.0189, respectively) were smaller than those between TrG and TrS (0.0857 and 0.0194, respectively). Analyses using CR for the same specimens showed that genetic distances were consistent with those obtained using microsatellite loci. These results, together with our previous observations, suggest that T. rubripes and T. chinensis are very closely related and possibly can be regarded as the same species. KeywordsGenetic diversity–Genetic differentiation–Microsatellite–Mitochondrial control region–Pufferfish– Takifugu
    Fisheries Science 01/2011; 77(1):59-67. · 0.90 Impact Factor
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    ABSTRACT: Objective: Pufferfish of the genus Takifugu are regional fish, found in narrow waters of northwestern Pacific Ocean. Among them, many are closely related which is especially true for two species such as torafugu T. rubripes and karasu T. chinensis. The two species have pronounced color pattern differences in their skin and anal fin: torafugu has some irregular black marks on a dorsal half of the posterior body part with white or pinkish anal fin, whereas karasu possesses no black marks on that body part with black anal fin. However, our previous study on these two species using several mitochondrial (mt) and nuclear genes showed their very close relationship. In addition, hybrid-like individuals which possess morphological features of both species are available in the culture system as well as in the nature. The present study was undertaken to detect genetic diversity of the two species at a population level using microsatellite markers and mt control region (CR). Materials and methods: Microsatellite genotyping was carried out by PCR for total DNA using three microsatellite markers reported by Furukawa et al. (2004) and one unpublished. Total DNA was extracted from liver and muscle tissues for torafugu from two wild torafugu populations [collected at Tsushima Island in 2003 (TT), n = 50 and Soneshinden, Kitakyushu in 2008 (ST), n = 50] and from anal fin tissues from one wild karasu population [collected on the east coast of Korea in 2004 (KK), n = 50]. The amplified PCR products were analyzed using QIAxcel system (QIAGEN, Irvine, CA, USA). Population study was performed using CR for the same 150 pufferfish specimens after direct sequencing. Data analyses were performed using Genepop v3.4 (Raymond and Rousset, 1995), TFPGA (Miller, 1997) and Fstat software (Goudet, 1995) for microsatellite loci, and Arlequin v3.0 (Excoffier et al. 2005) and DnaSP v4.0 software (Rozas et al. 2003) for CR. Results and discussion: All four microsatellite loci used were polymorphic and yielded a total of 138 different alleles. The genetic diversity index values of TT, ST and KK populations were 0.9505, 0.9350 and 0.9335, respectively. The values of genetic distance and genetic differentiation between TT and KK (0.0543 and 0.0189, respectively) were smaller than those between TT and ST (0.0857 and 0.0194, respectively). UPGMA dendrogram using microsatellite data also showed that TT formed one clade with KK, whereas ST was separated from this clade. Population dynamics study using CR yielded 161 variable sites (29%), resulting in 106 haplotypes. Haplotype diversity (h) was highest in ST population (0.9984 ± 0.0040) and lowest in KK (0.9118 ± 0.0260). Sequence diversity (π) also showed a similar trend among the three Takifugu populations. The genetic distance using CR between TT and KK populations was smaller (0.0821) than those between TT and ST populations (0.1473). Average pairwise difference was lowest between TT and KK (7.490) and largest between TT and ST populations (17.765). These results, together with our previous observation, suggest that torafugu and karasu are very closely related and hardly regarded as different species.
    Yearly conference of the Japanese Society of Fisheries Science; 03/2009
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    ABSTRACT: Among different pufferfish species, members of the genus Takifugu are closely related. This is especially true for torafugu T. rubripes and karasu T. chinensis. Although they have pronounced color-pattern differences in their skin and anal fin, e.g. white and black in torafugu and karasu, respectively, the availability of hybrid-like individuals having intermediate color patterns between the two fish lead to disputes arising in the Japanese fish markets from trade on species identification and classification. In the present study, we employed a suppression subtractive hybridization technique to identify genes involved in color differentiation between torafugu and karasu. A total of 145 clones were generated and 23 genes were putatively identified by homology search in BLASTx. RT-PCR analysis confirmed species-specific expression for two genes encoding Annexin 2a and C1q-like adipose specific protein and different levels of expression for three genes encoding IgM heavy chain constant region, MGC108117 and 40S ribosomal S17 protein. Annexin 2a has been reported to be expressed in mouse retinal pigment epithelium, and is a potential candidate for color-pattern differences between karasu and torafugu.
    WFC2008: 5th World Fisheries Congress; 10/2008
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    ABSTRACT: Sequence analyses of mitochondrial (mt) and nuclear genes were performed for genetic comparison between two Takifugu pufferfish species torafugu T. rubripes and karasu T. chinensis. With a sequence coverage of 20% in mtDNA, 640, 308, 344, 554 and 697 bp encoding mt 16S ribosomal RNA (rRNA), adenosine triphosphatase 6 (ATPase 6), nicotinamide adenine dinucleotide dehydrogenase subunit 4 (ND4), ND5 and cytochrome b (cyt b), respectively, among 24 wild torafugu, 24 wild karasu and 6 hybrid-like samples, 15% torafugu identified by external color patterns showed nucleotide sequences consistent with karasu. Meanwhile, sequences of 60% karasu were consistent with those registered for torafugu (AJ421455). As for the hybrid-like samples, we found two to possess karasu-specific sequences in some base positions while torafugu-specific in others. Remaining hybrid-like samples possessed torafugu-specific sequences. Mt control region, on the other hand, did not show such type of consistency. Analysis of nuclear melanocortin receptor genes (MC1R, MC4R) among 54 samples showed 99 - 100% inter- and intra-specific sequence identity. Partial nuclear 18S rRNA, complete internal transcribed spacer 1 (ITS1), partial 5.8S rRNA and ITS2 genes showed similar levels of identity, indicating very low level of variation in their respective gene fragments between the two Takifugu species.
    Fisheries Science 01/2008; 74:743-754. · 0.90 Impact Factor
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    ABSTRACT: Rotifers have been used to study the mechanisms of ageing for more than a century, but the underlying molecular basis of ageing in rotifers is largely unknown. The insulin/insulin-like growth factor (IGF-1) signaling pathway has been found to regulate the lifespan of evolutionarily distinct eukaryotes from yeast to mammals. We therefore assume that the insulin/IGF-1 pathway is a candidate for regulating the rotifer’s lifespan. Accordingly, we examined the action of an inhibitor to PI3-kinase involved in the pathway for the rotifer Brachionus plicatilis O. F. Müller. This kinase was first discovered as age-1 to regulate the longevity of Caenorhabditis elegans. As expected, the inhibitor treatment resulted in the extension of lifespan by 30% compared to the reference group without the treatment, whereas reproductive characters were not apparently changed. These results were consistent with those observed in C. elegans, suggesting that the lifespan of B. plicatilis is likely to be regulated by the signaling pathway involving PI3-kinase.
    Hydrobiologia 12/2004; 546(1):347-352. · 1.99 Impact Factor
  • Md. Shaheed Reza, Satoshi Furukawa, Shugo Watabe
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    ABSTRACT: A molecular approach was used to identify pufferfish, Takifugu rubripes which is considered as a fish of great commercial value. Recently, it has been reported that other pufferfish species of lower economic importance including T. chinensis and hybrid-like pufferfish enter Japanese fish markets in the name of T. rubripes. In an effort to prevent adulteration of fish species and to ensure consumers’ rights, a quick and reliable method is needed which will easily distinguish T. rubripes from other pufferfish species. Using the reported mtDNA sequence of T. rubripes and T. chinensis, we selected 16S rRNA, ATPase6, ND4 and ND5 loci which contain base-pair difference in at least two positions between these two species. We amplified these four loci using PCR and determined nucleotide sequences by direct sequencing. Among the nine different pufferfish samples under investigation, three samples showed consistency with T. chinensis, but the morphologically identified T. chinensis itself did not show similarity. Rather it was identified to be T. rubripes. This is an indication that morphological identification can be inconsistent with DNA sequence result between closely related pufferfish species. The rest five pufferfish samples which were suspected to be hybrids from their external color patterns on the skin, showed similarity with T. chinensis in some base positions, and in other positions showed similarity with T. rubripes. The results in our study suggest that speciation between T. rubripes and T. chinensis is not due to evident species difference but individual polymorphism. Our observation to distinguish T. rubripes and T. chinensis is needed to be further confirmed, because the present conclusion was derived from a small number of samples. We are currently analyzing newly obtained T. chinensis samples.
    TODAI International Symposium "Functional Genomics of Pufferfish - Recent Advances and Perspective"; 11/2004
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    ABSTRACT: The search for dinucleotide repeat microsatellites within scaffolds 1–25 of genome database JGI Fugu v3.0 for the pufferfish Takifugu rubripes revealed that 80% of microsatellite loci consisted of five to 13-fold repeats with locus-specific differences in density. Eleven out of 15 microsatellite loci isolated from the database with which genotyping using wild pufferfish was successfully performed showed polymorphism; that is, the means of the number of alleles and expected and observed heterozygosities at these 11 loci were 21.8, 0.915 and 0.829, respectively. It was confirmed that eight out of the 11 polymorphic loci were inherited through the Mendelian law and one pair of microsatellite loci derived from the same scaffold was linked. These results demonstrated that these loci are useful for constructing a linkage map in the pufferfish as DNA markers.
    Fisheries Science 08/2004; 70(4):620 - 628. · 0.90 Impact Factor
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    ABSTRACT: Torafugu Takifugu rubripes is an attractive vertebrate model organism for genomics by virtue of its smallest genome among vertebrates and available whole-genome database. Our group has constructed the torafugu linkage map with over 400 markers. In this study, we screened superior trait-related genes of torafugu by using the genome database and linkage map. Following two groups of genes were screened and analyzed, 1: Growth and muscle formation related genes, 2: Sex determining genes. (1) Quantitative trait loci (QTL) associated with high growth were screened by linkage analysis in crosses between a high-growth selected male and wild female. By using microsatellite markers, we identifi ed several loci which may relate to the high-growth trait. We also analyzed genes (MYHs) encoding myosin heavy chain, the most important functional molecule among muscle proteins. A comprehensive analysis on the genome database revealed at least 28 MYHs in torafugu, almost twice as many as in humans. Expression analysis of each MYH showed their developmental stage-specifi c and tissue-specifi c expressions. (2) By performing linkage analyses, we showed that the sex of torafugu is determined by a single chromosomal region named SDY on linkage group 19 in an XX-XY system.
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    ABSTRACT: The rotifer Brachionus plicatilis is an ecologically and commercially important species, and has been studied in various fields such as population dynamics, ecotoxicology and aging. However, recent studies have revealed that the B. plicatilis lineages involve an unknown number of cryptic species, and the group has been regarded as the Brachionus complex. One cause of this complicated taxonomy is the lack of surveys in the tropical zone, which is characterized by enormous species-richness. Accordingly, in this study we collected two Brachionus rotifers from the Sumatra and Sulawesi Islands, Indonesia, and determined their partial nucleotide sequences of mitochondrial DNA cytochrome c oxidase subunit I gene. Subsequently, we constructed molecular phylogenetic trees with fourteen species/lineages from four genera including the two Indonesian rotifers. The two Indonesian Brachionus rotifers were respectively found to be phylogenetically close to B. ibericus and B. rotundiformis. On the other hand, Japanese B. plicatilis was suggested to be phylogenetically closer to B. Manjavacas, which is proposed to be a new species, than to Spanish B. plicatilis. These results imply that the current taxonomy of the Brachionus is problematic, and a major revision is necessary to establish a reliable taxonomy of this group.

Publication Stats

31 Citations
6.51 Total Impact Points

Institutions

  • 2011
    • Bangladesh Agricultural University
      • Department of Fisheries Technology
      Mymensingh, Bangladesh
  • 2004–2008
    • The University of Tokyo
      • • Department of Aquatic Bioscience
      • • Faculty and Graduate School of Agriculture and Life Sceince
      Edo, Tōkyō, Japan