シンポジウムが行われた台湾トップの学術研究機関アカデミ
アシニカ内の「INSTITUTE OF
BIOMEDICAL SCIENCES」

熊本大学グローバルCOE の若手研究者による論文を紹介します。

Draxin is essential for tectum andretinocollicular axon projections. Developmental Biology.332(2) 351-359 August 2009

台湾を訪れた12名の
熊大G-COEメンバー

Naser Iftekhar Bin
COEリサーチ・アソシエイト
神経分化学分野

I have been working with a recently identified axon guid-since axon guidance molecules may also play importantance molecule draxin which plays important role in theroles in, for example, morphogenesis, blood vessel forma-development of spinal and forebrain commissures (Islam et.

tion, and in the immune system.

al 2009, science 323, 388-393).In the midbrain of chick andmouse, draxin is expressed from early embryonic stage in adorsal high to ventral low gradient. My data suggest that

人材育成の一環として若手研究者も参加
熊大G-COEでは、国際シンポジウムを若手

draxin might function as a repulsive guidance cue for theventrally directed axon projection in chick early embryonicbrain (Naser IB et al, 2009. Dev. Biol. 332, 351-359). Conたりにすることは、大きな刺激となります。

tinuous expression of draxin even after the midbrains ven-

研究者の育成において、貴重な機会と捉えてさらに、自分と同じポジションにいるアカ

trally directed axon projections were completed led me toいます。若手研究者が海外で研究発表を行い、デミアシニカの若手研究者の研究発表を聞

analyse the retinocollicular (tectum) projection in draxin

海外の研究者の発表を聞き、その考えに触れき、その内容のみならず、研究に対する姿勢を

knock out mice. Draxin was found to be essential for this

ることは、短期間で留学に代わる経験を積む

自分と対比させることで、モチベーションをwell analyzed system. draxin is expressed in the mouse

ことに値するといっても過言ではありませかきたてることにもなりました。

superior colliculas in a dorsal high to ventral low gradientん。今回は、公募によって若手研究者2名を選

during the time of retinocollicular map formation. Draxin出。この2名が経験したエントリーから準備期

今年度初となった今回のシンポジウムは、

inhibits neurite outgrowth from mouse retinal explant. draxin

間、発表までのプロセス、そして現地での発表

熊大G-COEとアカデミアシニカの友好関係

knock out mice shows clear mapping defect along theおよびディスカッションは、大きな経験となも深め、研究に関する情報を共有できたこと、

dorso-ventral and anterior-posterior axis of superior collicu-りました。

若手研究者に貴重な経験を積ませたことな

las. I believe revealing draxin's function will have a high

ど、大きな成果を上げることができました。こimpact not only in the developmental neurobiology

国際シンポジウムで発表するのは初めてとのような経験を、より多くの若手研究者に経

research field, but also in the wider context of cell biology

いう若手研究者にとって、このような機会を験してもらうために、熊大G-COEでは「若手与えられたことは、非常に貴重な経験となり研究者研究成果発表旅費支援」などの事業をました。熊大G-COEとアカデミアシニカの教行い、若手研究者の育成に力を入れています。

授たちの発表を間近で聞き、そこで交わされ今回のシンポジウムを皮切りに、今後も戦る教授たちの専門領域を越えた議論を目のあEvolutionary history and functional characterization of androgen
receptor genes in jawed vertebrates. Endocrinology.150(12) 5415-5427 December 2009

略的に国際交流事業を実施していきます。

12Fig 1: (A) Schematic representation of ventrally directed axonal tracts inchick midbrain (Chédotal et al., 1995). Mesencephalic (Mes) V neurons(black circles) present near the dorsal midline. They start to project axons
towards ventral direction from stage 14 and turn caudally in the ventraltectum. Tectobulbar neurons (open circles) also project axons toward
ventral direction and turn caudally before reaching the tegmentum andfollow the path of medial longitudinal fascicles. Dorsal tectum explants fromE4 embryos were co-cultured with mock transfected COS cell aggregate(B) and draxin transfected COS cell aggregate (C). Quantification of theaxonal growth of dorsal tectum explants cultured in collagen with mocktransfected COS cells or draxin transfected COS cells show a repulsive
activity of draxin. Significant differences were observed among proximal
sectors in the case of draxin compared with control cases. Vector GFP
DNA (D) or draxin cDNA (E) were over expressed in the ventral side of thetectum. Overlay picture shows that growth of axons was long and straight
through the GFP vector over expressed site (D, arrow). In fig E, tectum
axons were misrouted and stop by the over expressed draxin (E, arrow).

3

荻野由紀子／ Yukiko OginoCOEリサーチ・アソシエイト
生殖発生分野Vertebrates show diverse sexual characters in sexuallyby teleost ARβ. These findings indicate that the most

attractive and reproductive organs, which are regulated byancient type of AR, as activated by the classical androgens

steroid hormones, particularly androgens. However the evo-

as ligands, emerged before the Chondrichthyes-

lutionary history of Androgen receptor (AR) gene remains

Osteichthyes split, and the AR gene was duplicated during

largely unknown on the basis of phylogenic and functional

the TSGD event. We report here for the first time the accu-analyses. To elucidate the evolutionary history and func-

rate evolutionary history of AR gene and functional charac-tional diversification of AR genes in vertebrates, we cloned

terization of AR duplicates in teleost lineage.

the AR cDNAs from a shark, basal ray-finned fishes(Actinopterygii), namely bichir and sturgeon(Acipenseriformes), and teleosts including a basal teleost,arowana (Osteoglossiformes). Molecular phylogenetic analysis revealed that the gene duplication event that gave riseto two different teleost ARs (αandβ) likely occurred in theactinopterygian lineage leading to teleosts after the divergence of Acipenseriformes but before the split of Osteoglos4

56siformes, which is compatible with the phylogenetic timing of
teleost-specific genome duplication (TSGD). Searching for
AR genes in the medaka genome indicated that the teleostAR gene duplication has been associated with the duplication between chromosomes 10 and 14. Our functional analysis revealed that the shark AR activates the target gene via
androgen response element (ARE) by classical androgens.

1. 若手研究者（熊大講師 首藤さん）の発表。堂々たるもの 2. 聴講に訪れたアカデミアシニカの研究者や学生たち 3. シンポジウムでは、活発な議論が交わされた（熊大COEリサー
チ・アソシエイト 寺林さん） 4. 休憩時間は若手研究者同士のコミュニケーションの場（左：熊大COEリサーチ・アソシエイト 原田さん） 5. 広大な敷地のアカデミアシニカ内にはさまざまな研究所があり、高性能の研究器材や設備が整っている 6. 熊大G-COEのメンバー12名とアカデミアシニカのChen所長ら

3The teleost ARα showed the unique intracellular localization
with a significantly higher transactivating capacity than that4