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Chikusa ku, Japan

Ishijima J.,Laboratory of Animal Cytogenetics | Uno Y.,Laboratory of Animal Genetics | Nishida C.,Hokkaido University | Matsuda Y.,Laboratory of Animal Genetics | Matsuda Y.,Nagoya University
Cytogenetic and Genome Research

The W chromosome of ratite birds shows minimal morphological differentiation and retains homology of genetic linkage and gene order with a substantial stretch of the Z chromosome; however, the molecular structure in the differentiated region is still not well known. The kW1 sequence was isolated from the kiwi as a W-specific DNA marker for PCR-based molecular sexing of ratite birds. In ratite W chromosomes, this sequence commonly contains a ∼200-bp deletion. To characterize the very early event of avian sex chromosome differentiation, we performed molecular cytogenetic analyses of kW1 and its flanking sequences in paleognathous and neognathous birds and reptiles. Female-specific repeats were found in the kW1-flanking sequence of the cassowary (Casuarius casuarius), and the repeats have been amplified in the pericentromeric region of the W chromosomes of ratites, which may have resulted from the cessation of meiotic recombination between the Z and W chromosomes at an early stage of sex chromosome differentiation. The presence of the kW1 sequence in neognathous birds and a crocodilian species suggests that the kW1 sequence was present in the ancestral genome of Archosauria; however, it disappeared in other reptilian taxa and several lineages of neognathous birds. © 2014 S. Karger AG, Basel. Source

Nishida C.,Hokkaido University | Ishishita S.,Laboratory of Animal Genetics | Yamada K.,Hokkaido University | Griffin D.K.,University of Kent | And 2 more authors.
Cytogenetic and Genome Research

The osprey (Pandion haliaetus) has a diploid number of 74 chromosomes, consisting of a large number of medium-sized macrochromosomes and relatively few microchromosomes; this differs greatly from the typical avian karyotype. Chromosome painting with chicken DNA probes revealed that the karyotype of P. haliaetus differs from the chicken karyotype by at least 14 fission events involving macrochromosomes (chicken chromosomes 1-9 and Z) and at most 15 fusions of microchromosomes, suggesting that considerable karyotype reorganization occurred in P. haliaetus in a similar manner previously reported for Accipitridae. A distinct difference was observed, however, between Accipitridae and Pandionidae with respect to the pattern of chromosome rearrangements that occurred after fissions of macrochromosomes. Metacentric or submetacentric chromosomes 1-5 in P. haliaetus appear to have been formed by centric fusion of chromosome segments derived from macrochromosomal fissions. By contrast, many pairs of bi-armed chromosomes in Accipitridae species seem to result from pericentric inversions that occurred in the fission-derived chromosomes. Two families of repetitive sequences were isolated; the 173-bp PHA-HaeIII sequence occurred on all chromosomes, whereas intense signals from the 742-bp PHA-NsiI sequence were localized to all acrocentric chromosomes, with weak signals on most of the bi-armed chromosomes. Two repetitive sequences cohybridized in the centromeric heterochromatin; however, the sequences differed in unit size, nucleotide sequence and GC content. The results suggest that the 2 sequence families originated from different ancestral sequences and were homogenized independently in centromeres, and that a chromosome size-dependent compartmentalization may have been lost in P. haliaetus. © 2014 S. Karger AG, Basel. Source

Nishida C.,Hokkaido University | Ishijima J.,Hokkaido University | Ishishita S.,Laboratory of Animal Genetics | Yamada K.,Hokkaido University | And 3 more authors.
Cytogenetic and Genome Research

The karyotype of the Japanese mountain hawk-eagle (Nisaetus nipalensis orientalis) (2n = 66) consists of a large number of medium-sized and small chromosomes but only 4 pairs of dot-shaped microchromosomes, in contrast to the typical avian karyotype with a small number of macrochromosomes and many indistinguishable microchromosomes. To investigate the drastic karyotype reorganization in this species, we performed a molecular cytogenetic characterization employing chromosome in situ hybridization and molecular cloning of centromeric heterochromatin. Cross-species chromosome painting with chicken chromosome-specific probes 1-9 and Z and a paint pool of 20 microchromosome pairs revealed that the N. n. orientalis karyotype differs from chicken by at least 13 fissions of macrochromosomes and 15 fusions between microchromosomes and between microand macrochromosomes. A novel family of satellite DNA sequences (NNO-Apa I) was isolated, consisting of a GC-rich 173-bp repeated sequence element. The NNO-Apa I sequence was localized to the C-positive centromeric heterochromatin of 4 pairs of microchromosomes, which evolved concertedly by homogenization between the microchromosomes. These results suggest that the 4 pairs of dot-shaped microchromosomes have retained their genomic compartmentalization from other middle-sized and small chromosomes. © 2013 S. Karger AG, Basel. Source

Uno Y.,Laboratory of Animal Genetics | Asada Y.,Biosystems Science Course | Nishida C.,Hokkaido University | Takehana Y.,Japan National Institute for Basic Biology | And 2 more authors.
Cytogenetic and Genome Research

The large biarmed chromosomes of Oryzias celebensis [2n = 36, fundamental arm number (FN) = 48] are considered to have resulted from fusions of acrocentric chromosomes in the ancestral karyotype of Oryzias, which is retained in O. hubbsi (2n = 48, FN = 48). To understand the molecular evolution of heterochromatin associated with karyotype reorganization in medaka fishes, we cloned 3 and 6 novel families of heterochromatin-related repetitive DNA sequences from O. hubbsi and O. celebensis, respectively, and characterized them using molecular cytogenetics. Two AT-rich repetitive sequences isolated from the genomic DNA of O. hubbsi, a 164-bp satellite DNA (OHU-RsaI-Scen) and a 177-bp telomere-specific repeat (OHU-RsaI-Stelo), were shown to be major components of the constitutive heterochromatin of centromeres and telomeres, respectively. A GC-rich 326-bp sequence, named OHU-AluI-M1, was colocalized with the 18S-28S ribosomal RNA gene cluster to a single autosomal pair of chromosomes and the W chromosome. In O. celebensis, 2 major satellite DNA sequences (the AT-rich 157-bp OCE-AluI-Scen sequence and the 186-bp OCE-HinfI-Scen sequence) were identified in the centromeric regions of almost all chromosomes. The 197-bp OCE-HinfI-S6 sequence was located in the centromeric and distal and/or interstitial heterochromatin of almost all chromosomes, and the 191-bp OCE-HinfI-S8 sequence was located in 6 pairs of chromosomes. Constitutive heterochromatin on the short arm of large submetacentric chromosome 5 was composed of at least 3 different repetitive sequences: the 171-bp OCE-AluI-S18 sequence, the 197-bp OCE-HinfI-S6 sequence and the 172-bp OCE-HinfI-S11 sequence. All families of repeated sequences showed no nucleotide sequence similarity with each other and high species-specificity among 7 different species. These results suggest that the heterochromatin of O. hubbsi and O. celebensis consists of various types of repetitive sequence and that the sequences evolved independently and were then amplified site-specifically in each lineage after karyotype reorganization occurred in the ancestral karyotype. © 2013 S. Karger AG, Basel. Source

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