Molecular cloning and characterization of the repetitive DNA sequences that comprise the constitutive heterochromatin of the W chromosomes of medaka fishes
Molecular cloning and characterization of the repetitive DNA sequences that comprise the constitutive heterochromatin of the W chromosomes of medaka fishes
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DOI：
10.1007/s10577-011-9259-7
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发表时间：
2012-01-01
影响因子：
2.6
通讯作者：
Sakaizumi, Mitsuru
中科院分区：
文献类型：
--
作者：
Takehana, Yusuke;Naruse, Kiyoshi;Sakaizumi, Mitsuru
在青鳉属的青鳉中，大多数种类具有同形性染色体，但也有一些种类，如Oryziashubbsi和Oryziasjavanicus，具有异型性ZW性染色体。本研究从O. Hubbsi和染色体原位杂交和滤膜杂交鉴定。这个重复的元素，我们指定为BstNI家族元素，定位在异染色质区域的W染色体，以及两对常染色体。该元件的同源序列仅在O. javanicus是O. hubbsi，这表明这种重复的元素起源于这两个物种的共同祖先。而O. javanicus比O. hubbsi，以及该元件在O. javanicus局限于一对常染色体上的异染色质区域。因此，我们假设这个重复元件在O. hubbsi谱系，特别是在其W染色体上，在O.爪哇亚种谱系。此外，我们还发现18 S-28 S核糖体RNA基因在两种O. hubbsi和O.爪哇人。我们以前的研究表明，这些物种的性染色体没有连锁同源性，表明RNA基因是共享的W染色体之间的不同来源。这种情况可能是由易位的性别决定区与核糖体RNA基因在任一物种或独立的积累的RNA基因作为一个收敛的过程中W染色体变性。
Among the medaka fishes of the genus Oryzias, most species have homomorphic sex chromosomes, while some species, such as Oryzias hubbsi and Oryzias javanicus, have heteromorphic ZW sex chromosomes. In this study, a novel family of repetitive sequence was molecularly cloned from O. hubbsi and characterized by chromosome in situ and filter hybridization, respectively. This repetitive element, which we designated as a BstNI family element, localized at heterochromatin regions on the W chromosome, as well as on two pairs of autosomes. Homologous sequences to this element were found only in O. javanicus, which is a sister species of O. hubbsi, suggesting that this repeated element originated in the common ancestor of these two species. However, the intensity of the hybridization signals was lower in O. javanicus than in O. hubbsi, and the chromosomal location of this element in O. javanicus was confined to heterochromatin regions on one pair of autosomes. Thus, we hypothesize that this repetitive element was extensively amplified in the O. hubbsi lineage, especially on its W chromosome, after the separation of the O. javanicus lineage. In addition, we also found the W chromosomal location of the 18S-28S ribosomal RNA genes in both O. hubbsi and O. javanicus. Our previous studies showed no linkage homology of the sex chromosomes in these species, indicating that the RNA genes were shared between W chromosomes of different origins. This situation may be explained by a translocation of the sex-determining region with the ribosomal RNA genes in either species or an independent accumulation of the RNA genes as a convergent process during W chromosome degeneration.