{"created":"2023-06-20T13:20:53.081660+00:00","id":948,"links":{},"metadata":{"_buckets":{"deposit":"d1412a7e-6564-4bf9-bd77-647f83c17935"},"_deposit":{"created_by":1,"id":"948","owners":[1],"pid":{"revision_id":0,"type":"depid","value":"948"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00000948","sets":["2:430:20"]},"author_link":["9993","9994","9995"],"item_1_creator_2":{"attribute_name":"著者名","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"磯部, 拓"}],"nameIdentifiers":[{}]}]},"item_1_creator_3":{"attribute_name":"フリガナ","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"イソベ, タク"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2000-03-24"}]},"item_1_degree_grantor_5":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_name":"総合研究大学院大学"}]}]},"item_1_degree_name_6":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士（理学）"}]},"item_1_description_12":{"attribute_name":"要旨","attribute_value_mlt":[{"subitem_description":"In mammals, the mouse major histocompatibility complex (MHC) is the only region where breakpoints of meiotic recombination are systematically studied at the molecular level.  In the class II region of the MHC, meiotic recombination does not occur at random but are clustered in limited regions known as hotspots.  Outside of the hotspots, where recombination scarcely occurs, is called cold regions.<br />  Thus far, four hotspots have been identified in the MHC class II  region.  The presence or absence of a hotspot depends on the MHC haplotype involved in genetic crosses used to detect recombination.  Among the four hotspots, three hotspots have been well characterized at molecular level and their nucleotide sequences were determined.  Comparison of the sequences indicated several molecular motifs, such as middle repetitive sequence of MT-family, a sequence similar to a transcription factor binding motif and TCTG or CCTG tetrtamer repetitive sequence, are commonly observed in the three hotspots.  It was also reported that the hotspot regions are not always hypersensitive sites to endonuclease Dnase I  (Mizuno et al.  1996), suggesting that chromatin structure of the hotspots is not open.  Despite studies over almost 15 years since the discovery of the hotspots and findings mentioned above, the mechanism by which the recombinations in this region are restricted to the hotspot is not still clear.<br />  In this study, I attempted to address this question by combining of molecular genetical approach and a recently developed cytogenetical approach.  First, I carried out the molecular genetical analysis to reveal the structure of the hotspot in the vicinity of Pb gene, which has been left untouched for a long time.  The result of this study indicated that the breakpoints of the recombinations are confined to a very short segment of DNA as seen in other three hotspots.  Subsequently, comparing the sequences of all four hotspots, I tried to find general features of their molecular structure.  From this analysis, I found that all four hotspots were located either in introns or at 3' end of genes, gut not all 5' end of genes.<br />  In addition, I searched molecular motifs shared by the hotposts in more systematic way.  To do this, I surveyed a 1.3Mb nucleotide sequence of the whole MHC class II  region, which was recently deposited to database, as well as sequences of the all four hotspots.  As a result, it appeared that Eb, Lmp2, Pb hotspots have MT family sequences, and that all four hotsopts have a octamer transcription factor binding motif designated as O motif, B motif-like sequences that is similar to another transcription factor biding motif and the tetramar repetitive sequence.  The direction of the O motif and the B motif-like sequences is opposite.  The distance between these two motifs is within 300bp in all four hotspots.  The tetramer repetitive sequences are located in DNA segments less than 1.2kb in length, which contain the O motif and the B motif-like sequences as well.  It is notable that these motifs are also found in a hotspot identified in the mouse MHC class III region, as well as a hotspot identified in the vicinity of TAP2 gene in the human MHC class II  region.  All these findings contrast the well established characterizations of the hotspots in budding yeast, Saccharomyces cerevisiae.  In budding yeast, their hotspots are located in promoter regions at the 5' end of genes, which are overlapped with hypersensitive sites to endonuclease DNase I  and MNase.  Any consensus sequences shared by the yeast hotspots are known.<br />  In meiosis, chromatin forms special structure, which shows dynamic changes during the stages of meiosis.  In the early stage, sister chromatides remain associated with each other (zygotene to pachytene stage).  Then, two copies of homologous chromosome behave in a coordinated fashion.  Homologous chromosomes must find their proper partners and physically pair with them along their structure known as the synaptonemal complex (SC).  SC consists of the core region and chromatin loops that are anchored to the core region.<br />  It is established that RecA homologs, Rad51 and Dmc1 proteins, play central roles in the meiotic recombination.  In mouse, both of Rad51 and Dmc1 are observed on the chromatin from the leptotene to the zygotene stage (Ikeya et al.  1997).  In the zygotene stage, the protein complex known as early recombination nodule is observed on the inside of the two axial elements.  In the pachytene stage, Rad51 protein is localized along the core of SC, and the late recombination nodule, which is protein complex larger than the early recombination nodule, is observed exclusively along the core of the SC.  At the stage of segregation of the SC (diplotene to diakinesis stage), chiasmata that are stable connections between homologs and are thought to be cross over points can be seen.  Then chiasmata are disassembled and recombination intermediates are resolved.  Number of the late recombination nodules is almost equal to chiasmata, implying that the sites of the late recombination nodule are cross over points.  This is also supported by the observation that the Rad51 proteins localized on the late recombinaiton nodules along the core of SC.<br />  Previous reports suggested that special sequences play a role in pairing homologous chromosomes in meiosis.  For example, painting of the X and Y chromosomes in Drosophila melanogaster is mediated by the rDNA repeats, which are bpresent in two tandem clusters, one in the centromeric X heterochromatin and the other near the teromere of the short arm of the Y chromosome.  A block of the tandem repeats on the X chromosome interacts with a similar block on the Y chromosome.  Analysis of flies containing transgenic insertions of the rDNA has demonstrated that a 240bp sequence located in the intergenic spacer region of the rDNA is necessary and sufficient for the pairing (Ren et al.  1997).  This report indicates that special sequences act to determine the pairing sites of homologous chromosomes.<br />  If, in deed, these special sequences are able to initiate chromosome pairing, it is possible that regions containing such sequences become recombination hotspots.  The hotspots in the mouse MHC are not found in promotor regions of 5' end of genes, where in budding yeast double-strand breaks (DSBs) of DNA occurs and recombination reaction i itiates.  This fact also supports the idea that unlike budding yeast , the locations of hte mouse hotspots are determined by the specificity of chromosome pairing sites but not of initiation istes of recombination reaction by DFSBs.  If this is the case, it is expected that the mouse hotspots DNA tends to be localized closer to the SC core than cold region DNA in the pachyten stage.  In this study, in order to examine this possibility, I carried out cytogenetical analysis to observe topological location of the hotspot and the cold region in relative to the cold region and immuno-staining with antibody for the SC core demonstrated that the hotspot signals localize closer to the SCD core than the signals of the cold region.  This result indicates that mouse chromatin loop is not randomly attached to the SC core and the possibility that the hotspot region is specifically used as a landmark in the chromosome pairing, which determines the site of recombination.","subitem_description_type":"Other"}]},"item_1_description_18":{"attribute_name":"フォーマット","attribute_value_mlt":[{"subitem_description":"application/pdf","subitem_description_type":"Other"}]},"item_1_description_7":{"attribute_name":"学位記番号","attribute_value_mlt":[{"subitem_description":"総研大甲第463号","subitem_description_type":"Other"}]},"item_1_select_14":{"attribute_name":"所蔵","attribute_value_mlt":[{"subitem_select_item":"有"}]},"item_1_select_8":{"attribute_name":"研究科","attribute_value_mlt":[{"subitem_select_item":"生命科学研究科"}]},"item_1_select_9":{"attribute_name":"専攻","attribute_value_mlt":[{"subitem_select_item":"18 遺伝学専攻"}]},"item_1_text_10":{"attribute_name":"学位授与年度","attribute_value_mlt":[{"subitem_text_value":"1999"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"ISOBE, Taku","creatorNameLang":"en"}],"nameIdentifiers":[{}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲463_要旨.pdf","filesize":[{"value":"402.1 kB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"要旨・審査要旨 / Abstract, Screening Result","url":"https://ir.soken.ac.jp/record/948/files/甲463_要旨.pdf"},"version_id":"cb348ad5-901f-419a-92a0-a24fcda2714b"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲463_本文.pdf","filesize":[{"value":"1.9 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文","url":"https://ir.soken.ac.jp/record/948/files/甲463_本文.pdf"},"version_id":"5fd9b52a-9119-4647-9dcf-b63e63b2202e"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"jpn"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"thesis","resourceuri":"http://purl.org/coar/resource_type/c_46ec"}]},"item_title":"マウスＭＨＣクラス・領域における減数分裂期組換えのホットスポットの遺伝学的解析","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"マウスＭＨＣクラス・領域における減数分裂期組換えのホットスポットの遺伝学的解析"}]},"item_type_id":"1","owner":"1","path":["20"],"pubdate":{"attribute_name":"公開日","attribute_value":"2010-02-22"},"publish_date":"2010-02-22","publish_status":"0","recid":"948","relation_version_is_last":true,"title":["マウスＭＨＣクラス・領域における減数分裂期組換えのホットスポットの遺伝学的解析"],"weko_creator_id":"1","weko_shared_id":1},"updated":"2023-06-20T14:41:44.770787+00:00"}