{"created":"2023-06-20T13:20:58.334371+00:00","id":1044,"links":{},"metadata":{"_buckets":{"deposit":"8b4a4923-cdbc-4899-90f6-49081853df0e"},"_deposit":{"created_by":1,"id":"1044","owners":[1],"pid":{"revision_id":0,"type":"depid","value":"1044"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00001044","sets":["2:430:20"]},"author_link":["0","0","0"],"item_1_creator_2":{"attribute_name":"著者名","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"荻沼, 政之"}],"nameIdentifiers":[{}]}]},"item_1_creator_3":{"attribute_name":"フリガナ","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"オギヌマ, マサユキ"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2008-03-19"}]},"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":" During mouse embryogenesis, many morphogenetic events occur sequentially
according to the scheduled time, indicating that these sequential events are linked
with the precise temporal regulation. Such regulations must exist throughout
embryogenesis to coordinate many developmental processes, although the molecular
nature coordinating such temporal regulation is largely unknown.
The vertebrate body is subdivided into repeating segments along the
anterior-posterior (AP) axis. This segmental or metameric pattern is established early
in embryogenesis by the process of somitogenesis. Somites are blocks of paraxial
mesoderm cells that give rise to the axial skeleton and their associated muscles and
tendons, which retain a metameric pattern. During development, somitogenesis is
tightly coupled with axis elongation. Precursors of the somites, called presomitic
mesoderm (PSM), arise from the posterior end of embryo, called tail bud. Somites are
aligned along the neural tube, and budding off from the anterior-most end of the
unsegmented presomitic mesoderm at the regular time. Therefore, somitogenesis is an
event that occurs according to the scheduled time, and it is believed that somitogenesis
is under the precise control of temporal information.
The timing of somitogenesis is regulated by the so-called `segmentation clock',
which is associated with a periodic activation of Notch signal pathway in PSM cells.
Notch signal .activates the target genes, Hes7 and L-fng. The transcription factor Hes7
(hairy and enhancer of split 7) in turn represses own transcription as well as that of
L-fng, making negative feedback loops. L-fng encodes a glycosyltransferase that acts
as a negative regulator of Notch activity, which generates the oscillation of Notch
signal activity within the PSM. However, the oscillation itself does not make a
segmental boundary, as exemplified by a pendulum clock in which the correct time is
not provided by the rhythm of pendulum. This temporal information has therefore to
be accurately translated into a spatial pattern during somitogenesis.
The basic helix-loop-helix (bHLH) protein Mesp2 is a crucial factor in this process.
Mesp2 expression is periodically observed only in the anterior PSM, and the anterior
border of the Mesp2 expression domain determines the next somite segmental border.
To understand dynamic expression of Mesp2, the enhancer sequence, which is required
for the expression in the PSM, has been mapped within 185bp upstream region in the 5'
flanking region of Mesp2 gene, and it has been shown that a T-box transcriptional
factor, Tbx6, directly binds to the enhancer elements, and is essential for the
activation of Mesp2. Furthermore, it is shown that Notch signaling synergistically
works with Tbx6 and enhances Mesp2 activation when these factors coexist. However,
since the enhancer analysis was mainly conducted using the cultured cell system,
mechanisms involved in the spatial restriction and periodic regulation of Mesp2
expression remain elusive.
In this study, I have employed high resolution fluorescent in situ hybridization in
conjunction with immunohistochemical methods to analyze sections derived from
single specimens. These methods have enabled me to determine the spatio-temporal
relationship among several factors involved in mouse somitogenesis. Initially I show
that the timing of Mesp2 expression is determined by the periodic waves of Notch
activity, indicating the temporal link between Notch signal oscillation and Mesp2
transcription cycle. Next, I find that Tbx6 defines the anterior limit of Mesp2
expression domain by serving as an important transcription activator. Intriguingly,
Mesp2 mRNA initially shares an identical anterior border, but that once translated,
the Mesp2 protein is found to suppress Tbx6 expression post-translationally. This was
strongly supported by the fact that Tbx6 protein expression was expanded to the
anterior somitic region in the Mesp2-null embryo without altering expression pattern
of the transcript. The negative regulation of the Tbx6 by Mesp2 is critically important
to set up the next anterior border of Mesp2 expression domain. These results indicate
that interactions of three factors, Mesp2, Tbx6 and Notch activity are critically
important to translate temporal information to the spatial patterning. I also find that
onset of Mesp2 transcription is intimately linked with the initiation of Notch signal
oscillation, indicating that the relationship of three factors appears to be established
in the early stage embryo via initial Notch oscillation. I further show that the lack of
FGF signaling results in the posterior shift of Mesp2 expression domain, indicating
that FGF signaling provides a spatial cue to position the posterior border of Mesp2
expresslon.
Furthermore, to reveal the mechanism of post-translational Tbx6 suppression
downstream of Mesp2, I tried to determine the domain of Tbx6 protein that was
required for the suppression process. I generated transgenic mice harboring several
types of Tbx6 protein that had truncation in several domains, under the control of
endogenous promoter and enhancers of Tbx6 using a BAC-base transgenic mouse
technology. These results indicate that the T-box domain containing a DNA-binding
motif, is essential and sufficient for the suppression of Tbx6 expression. In good
agreement with these results, I find that Mesp2 also suppresses the expression of
Brachyury, the other T-box factor protein, by the post-translational mechanism.
Taken together, I conclude that Mesp2 is the final output signal by which the
temporal information from the segmentation clock is translated to the segmental
patterning, and reciprocal regulation between Mesp2 and Tbx6 creates the periodic
pattern during somitogenesis.
","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1162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":"2007"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"OGINUMA, Masayuki","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1162_要旨.pdf","filesize":[{"value":"334.2 kB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"要旨・審査要旨","url":"https://ir.soken.ac.jp/record/1044/files/甲1162_要旨.pdf"},"version_id":"ef6be7c8-3c9a-4cda-a026-507181b241c7"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1162_本文.pdf","filesize":[{"value":"3.0 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文","url":"https://ir.soken.ac.jp/record/1044/files/甲1162_本文.pdf"},"version_id":"bd18617f-4186-45d4-8547-40f43b1db895"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"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":"Mesp2 and Tbx6 cooperatively establish periodic patterns, coupled with the clock machinery during mouse somitogenesis","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Mesp2 and Tbx6 cooperatively establish periodic patterns, coupled with the clock machinery during mouse somitogenesis"},{"subitem_title":"Mesp2 and Tbx6 cooperatively establish periodic patterns, coupled with the clock machinery during mouse somitogenesis","subitem_title_language":"en"}]},"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":"1044","relation_version_is_last":true,"title":["Mesp2 and Tbx6 cooperatively establish periodic patterns, coupled with the clock machinery during mouse somitogenesis"],"weko_creator_id":"1","weko_shared_id":-1},"updated":"2023-06-20T16:09:47.668275+00:00"}