{"created":"2023-06-20T13:21:28.306432+00:00","id":1689,"links":{},"metadata":{"_buckets":{"deposit":"6355047a-679f-4a00-89a1-4c738c93754b"},"_deposit":{"created_by":21,"id":"1689","owners":[21],"pid":{"revision_id":0,"type":"depid","value":"1689"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00001689","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":"鈴木, 郁夫"}],"nameIdentifiers":[{}]}]},"item_1_creator_3":{"attribute_name":"フリガナ","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"スズキ, イクオ"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2010-03-24"}]},"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":"A remarkable feature of the mammalian evolution is the expansion of the
neocortex and emergence of the specific internal cytoarchitecture, the layer
structure. All of the mammalian species share the neocortical layer structure, in
which a similar type of neurons are arranged in a particular layer parallel to the
brain surface. During the neocortical de-velopment, the neuronal subtypes in the
neocortical layers are produced from neural progenitor cells in a stereotyped
temporal sequence from deep to upper layers. This stereotyped sequence of
neuronal production is attributed to the temporal restriction of the competence
of neural progenitors. The progenitors initially possess the multipotency to
generate the neuronal subtypes in all neocortical layers, but gradually loose the
potency during the development, and eventually become only able to produce the
upper layer neurons.
The dorsal region of the telencephalon called the pallium is the
non-mamalian homologue of the neocortex, because the same developmentally
important genes are commonly expressed in the mammalian neocortex and the
non-mammalian pallium. Although the pallium is completely conserved among
the vertebrates, the internal structure is variable. For example, the bird, one of
the closest relatives of the mammals, possesses the well-developed pallium
packed with distinct subtypes of neurons that are arranged in particular
domains. Such observations suggest that the common ancestor of the mammals
and the birds had already acquired the pallium, and that the pallial structure
has been modified in an animal group-specific manner through alterations in the
developmental processes. Therefore, a key event contributing to the evolutionary
emergence of the neocortical layer structure could be found through comparison
of the development between the mammalian neocortex and the non-mammalian
pallium.
The chick pallium is a good model to approach the problem, because of the
closest phylogenetic position to the mammals as well as the convenience of
experimental manipulations. For over a century, it has been argued whether the
avian pallium has a comparable neuronal repertory to the mammalian neocortex.
Therefore, I first checked expression patterns of marker genes for the
mammalian neocortical layers in the chick pallium. This analysis revealed that
both the deep (layer V) and upper layer (layer II/III) marker genes were
expressed in the chick pallium, suggesting that the chick pallium possesses a
neuronal repertory similar to the mammalian neocortex. In addition to the
molecular expressions, the axon projections were also found to be partially
similar between the chick pallial neurons and the corresponding neuronal
subtypes of the mammalian neocortex. In spite of the remarkable conservation
in the neuronal repertory, spatial distribution patterns of the deep and upper
layer neurons were entirely different from the layer arrangement of the
mammalian neocortex; in the chick pallium, the deep and upper layer neurons
were not arranged in parallel, but distantly located in the medial and lateral
side, respectively.
The development of the deep and upper layer neurons in the chick pallium
was investigated in detail. First, the birthdate analysis by BrdU pulse-labeling
demonstrated that the deep layer neurons were generated earlier than the
upper layer neurons in the chick pallium, suggesting that the temporal sequence
of the neuron production is evolutionarily conserved between the mammals and
the birds. Second, the fate mapping analysis revealed that the deep and upper
layer neurons originated from the distinct neural progenitors on the medial and
lateral sides in the chick pallium, respectively. This spatially separate
production of the neurons is the critical difference from the mammalian
neocortical development, in which the deep and upper layer neurons are
uniformly produced across the entire neocortex. Probably related to this
difference, I found that the late neurogenesis in the chick pallium
predominantly occurs on the lateral side. This spatiotemporally biased neuronal
production can explain the selective generation of the late-born upper layer
neurons only from the lateral side in the chick pallium. Taken together, the
distinct neurogenetic properties between the medial and lateral progenitors
appeared to be the key to construct the non-layered domain-like cytoarchiteture
in the chick pallium.
How then is the medio-lateral difference of neurogenetic properties is
instructed in the chick pallium? I cultured neural progenitor cells from the
medial and lateral sides of the chick pallium in a clonal density, and
surprisingly found that most of the clones derived from a single progenitor cell
contained both deep and upper layer neurons, regardless of its origin. This
remarkable observation clearly demonstrated that the neural progenitor cells in
the medial and lateral sides of the chick pallium intrinsically possess a similar
neurogenic competence, and the neurocompetency is extrinsically regulated by
the surrounding tissues according to the spatial positions.
On the basis on the results obtained, I propose the following model for the
avian pallial development. The avian neural progenitors are intrinsically
equivalent to those of mammals and capable of sequentially generating a full
repertory of neuronal subtypes. However, the neurogenesis in the avian pallium
is extrinsically regulated by two potential mechanisms. First, the deep layer fate
in the early-born neurons on the lateral side is suppressed by environmental
factors, and thereby, the lateral neural progenitor cells produce only the upper
layer neurons in the later phase of neurogenesis. Second, the medial neural
progenitors terminate the neurogenesis precociously before producing the upper
layer neurons leading to the preferential generation of deep layer neurons from
the medial side.
Lastly, the emergence of the layered neocortex in mammals has been a
long-standing mystery in evolutionary biology. The present discovery of the
evolutionary conservation in the neural progenitor competence between the
mammals and the avian suggests that the common ancestor of the amniotes has
already possessed the developmental potential to sequentially produce the
multiple neuronal subtypes. During the evolutionary diversification into each
lineage of animal groups, alterations in the spatial regulation of the
neurogenetic program may have contributed to the emergence of animal
group-specific brain structures, such as the layer structure in the mammalian
neocortex and the domain structure in the avian pallium.","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1343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":"2009"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"SUZUKI, Ikuko","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1343_要旨.pdf","filesize":[{"value":"359.8 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/1689/files/甲1343_要旨.pdf"},"version_id":"d49bba6f-5571-4a3e-9d25-d17cf033642a"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1343_本文_①.pdf","filesize":[{"value":"461.5 kB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文_①","url":"https://ir.soken.ac.jp/record/1689/files/甲1343_本文_①.pdf"},"version_id":"ffc2dfaf-a3bf-4eb6-b042-bcb3d21c7fb9"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1343_本文_②.pdf","filesize":[{"value":"294.7 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文_②","url":"https://ir.soken.ac.jp/record/1689/files/甲1343_本文_②.pdf"},"version_id":"0a10029c-f427-4f9e-8913-14185faa9bea"}]},"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":"Conservation of developmental mechanisms in evolutionarily divergent brain structures","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Conservation of developmental mechanisms in evolutionarily divergent brain structures"},{"subitem_title":"Conservation of developmental mechanisms in evolutionarily divergent brain structures","subitem_title_language":"en"}]},"item_type_id":"1","owner":"21","path":["20"],"pubdate":{"attribute_name":"公開日","attribute_value":"2011-01-19"},"publish_date":"2011-01-19","publish_status":"0","recid":"1689","relation_version_is_last":true,"title":["Conservation of developmental mechanisms in evolutionarily divergent brain structures"],"weko_creator_id":"21","weko_shared_id":-1},"updated":"2023-06-20T15:57:01.728293+00:00"}