Molecular Evolution and Systems Biology Study of Hypoxia-Inducible Signaling Pathway in Embryonic Development (III)

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Project title

Code/計畫編號

NSC101-2627-B019-001

Translated Name/計畫中文名

從分子演化及系統生物學角度探討胚胎發育時期低氧細胞訊息路徑的功能與調控機制-總計畫及子計畫4----斑馬魚發育時期HIFs的訊息路徑與生物功能區別(III)

Project Coordinator/計畫主持人

Chin-Hwa Hu

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Bioscience and Biotechnology

Website

https://www.grb.gov.tw/search/planDetail?id=2664156

Year

2012

Start date/計畫起

01-08-2012

Expected Completion/計畫迄

01-07-2013

Bugetid/研究經費

1500千元

ResearchField/研究領域

生物技術(理)

氧氣是維持生命不可或缺的重要分子，在正常氧氣供應（常氧）的環境下，細胞透過有氧呼吸提供了生物所需能量。當環境中的氧氣濃度降低造成低氧壓力時，會引起細胞內的各種代謝生理作用發生改變，以適應低氧環境的緊迫壓力，但亦可能會產生各種病理變化。在生物體內，這些低氧壓力的適應主要靠細胞內的HIFs （hypoxia-inducible factors)作用，啟動下游各相關基因的表現。HIFs是由α與β兩種不同次單元所組成，在斑馬魚內共有3種HIFα基因，均在發育時期廣泛表現在多種細胞內。我們在本計畫中針對斑馬魚的HIF1α與HIF2α基因，分別從逆向遺傳學、功能性基因體學的角度分別探討這些基因在胚胎發育的基因調控網路中所扮演的功能。我們在斑馬魚胚胎內發現Hif2α會透過細胞內抗凋亡基因survivins（birc5a與-5b）的表現，保護中樞神經細胞並促進其先驅細胞的分化。這項研究首次證實細胞低氧訊息系統在正常生理狀況下（常氧環境）直接控制細胞的生長與分化作用。此外Hif2α也參與了神經細胞內neuroD基因家族的調控。將hif2α基因默化會降低視網膜神經中多個neuroD基因被抑制，因而造成視網膜神經的分化停止。而外源性neuroD mRNA的表現亦可以回復hif2α基因默化胚胎（hif2α MO）視網膜神經的發育。在另一方面，我們的研究中發現Hif2α會透過liver-enriched gene-1（Leg1）的控制，完成肝臟發育後期組織擴展（outgrowth）的工作。當Hif2α的表現被抑制時，leg1的表現受到抑制，同時肝臟的發育萎縮而停留在未成熟的分化階段。在Hif1α方面，我們發現在斑馬魚胚胎內初期紅血球的發育過程中Hif1α參與了血球細胞生長與分化過程中的多項關鍵基因的調控工作，並負責擔任造血細胞內統整性的關鍵角色，負責協調血球先驅細胞從生長到分化過程中各項工作的穩定平衡。例如調控胚胎內紅血球生成素EPOerythropoietin）與攜鐵蛋白transferrin的表現、控制血球細胞內血基質（heme）合成酵素ALAS2與攜鐵蛋白接受器transferrrin receptor的表現等。在過去三年內，我們總共發表了五篇SCI論文，其中三篇為責任作者。目前正撰寫另外三篇論文中。 Oxygen is the most important molecule in our life, which can provide pivotal biological energy through an aerobic respiration system. When the organism is under hypoxia stress, it will make some physiological changes, such as metabolic switch, anaerobic respiration change, enhancing metabolic efficiency, increasing erythropoietic and angiogenic processes as well as inhibiting apoptosis. Prolonged hypoxia stress will cause severe pathological effects, or even death. Most of cellular hypoxia-responses are mediated by hypoxia-inducible factors (HIFs) to mediate its downstream gene transcriptions. The HIFs are heterodimeric transcription factors consisting with an oxygen-regulated α subunit and a constitutively expressed β subunit (HIF1β/ARNT).Via reverse genetic and functional genomic studies, here we investigated the functions of HIF1α and HIF2α in the genetic regulatory network during embryonic development. Our recent studies revealed that the cellular hypoxia-signaling system has some critical functions during zebrafish development, including neural survival and differentiation, erythropoiesis, liver outgrowth, and retinal development. It suggests that even with low level of HIFα factors, the hypoxia-signaling system still plays critical biological functions in normoxia environment. Specifically, we found that HIF2-related pathway protects CNS neural cells against apoptosis and promotes neuronal differentiation through tha activation of its downstream survivin (including birc5a and -5b) expression. In addition, HIF2α also controls neurod transcription. Knockdown hif2α translation abrogates neuroD expression and prevents neuronal differentiation. Ectopic neuroD cRNA rescued CNS and retinal development in hif2α morphants. Our results suggests there is a close coordination network between neurod, survivin and hif2α expressions during neuronal differentiation. In addition to the neural development, HIF2α also involves in liver development through the activation of leg1 (liver enrich gene-1). Knockdown hif2α abrogated leg1 transcription and prevented liver outgrowth. For the erythropoiesis, HIF1α plays a key role in coordinating stem cell proliferation, differentiation, iron homeostasis, heme biosynthesis, and globin gene transcription. In summary, we have published 5 papers, including 3 papers as corresponding author, during 2011-2013. Currently, there are 3 manuscripts are under prepared.

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Molecular Evolution and Systems Biology Study of Hypoxia-Inducible Signaling Pathway in Embryonic Development (III)

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