促存活蛋白Mcl-1在Tie2+細胞譜系之功能探討

Mcl-1屬於Bcl-2蛋白家族中具有抗細胞凋亡功能的一員，在諸多受調控的細胞生死程式中扮演重要的上游角色。老鼠若全身性缺乏Mcl-1蛋白，會造成胚胎在著床前後死亡。在這篇論文中，我們利用Cre-loxP系統將內皮細胞譜系中的mcl-1基因剔除。以Tie2-cre將內皮細胞部份的mcl-1剔除後，會造成大部分的胚胎死亡：Tie2-cre;mMcl-1f/ko突變鼠的比例從E13.5以後開始明顯下降，但有部分突變鼠可以存活到出生後。組織切片分析顯示，這些條件性基因剔除小鼠的心臟發育有嚴重的延遲現象，其中ㄧ隻還帶有與先天性心臟缺損相似的缺陷。然而，再經由更細部的分析之後，我們未能在Tie2-cre;mMcl-1f/ko突變鼠的心內膜墊(endocardial cushion)中觀察到不正常的間葉細胞(mesenchymal cell)增生或凋亡亦或是神經脊細胞(neural crest cell)遷移的異常。存活的Tie2-cre;mMcl-1f/ko突變鼠經由心臟超音波檢查發現，主動脈血液回流以及和主動脈狹窄相似的表現型。這些結果暗示了內皮細胞所表現的Mcl-1蛋白在胚胎心臟發育和維持成熟心臟的正常功能中扮演了重要的角色。我們仍然需要更多的實驗來說明Mcl-1蛋白如何實行這些功能。

關鍵字

Mcl-1 ；細胞凋亡；內皮細胞譜系；小鼠；心臟發育

並列摘要

Myeloid cell leukemia-1 (Mcl-1) is an anti-apoptotic member of the Bcl-2 protein family, which plays an apical role in many regulatory programs of cell death and survival. Mcl-1 deficiency results in peri-implantation lethality. Here, we employed the Cre-loxP system to conditionally knockout mcl-1 in the endothelial cell lineage. Tie2-cre-mediated deletion of mcl-1 leads to embryonic lethality with incomplete penetrance, with the expected frequency of Tie2-cre;mMcl-1f/ko conditional knockout embryos decreasing dramatically after E13.5. Histological analysis revealed that these conditional knockout embryos demonstrate a severe delay in heart development and one of them manifested defects mimicking congenital heart defects. However, detailed analysis revealed that cell proliferation and survival of mesenchymal cells in the endocardial cushion as well as migration of neural crest cell appeared to be normal in these mutant mice. The survived adult conditional knockout mice showed aortic regurgitation and an aortic stenosis-like phenotype. These results suggest a crucial role of endothelial Mcl-1 in embryonic heart development and maintaining normal heart functions during the adulthood. How Mcl-1 carries out these functions remains to be determined.

並列關鍵字

Mcl-1 ； anti-apoptotic member ； Cre-loxP system ； endothelial cell lineage ； heart development

參考文獻

Altmeyer, A., Simmons, R.C., Krajewski, S., Reed, J.C., Bornkamm, G.W., and Chen-Kiang, S. (1997). Reversal of EBV immortalization precedes apoptosis in IL-6-induced human B cell terminal differentiation. Immunity 7, 667-677.

Bae, J., Donigian, J.R., and Hsueh, A.J. (2003). Tankyrase 1 interacts with Mcl-1 proteins and inhibits their regulation of apoptosis. J Biol Chem 278, 5195-5204.

Bae, J., Leo, C.P., Hsu, S.Y., and Hsueh, A.J. (2000). MCL-1S, a splicing variant of the antiapoptotic BCL-2 family member MCL-1, encodes a proapoptotic protein possessing only the BH3 domain. J Biol Chem 275, 25255-25261.

Bamforth, S.D., Braganca, J., Eloranta, J.J., Murdoch, J.N., Marques, F.I., Kranc, K.R., Farza, H., Henderson, D.J., Hurst, H.C., and Bhattacharya, S. (2001). Cardiac malformations, adrenal agenesis, neural crest defects and exencephaly in mice lacking Cited2, a new Tfap2 co-activator. Nat Genet 29, 469-474.

Bamforth, S.D., Braganca, J., Farthing, C.R., Schneider, J.E., Broadbent, C., Michell, A.C., Clarke, K., Neubauer, S., Norris, D., Brown, N.A., et al. (2004). Cited2 controls left-right patterning and heart development through a Nodal-Pitx2c pathway. Nat Genet 36, 1189-1196.

國際替代計量

促存活蛋白Mcl-1在Tie2+細胞譜系之功能探討

全文下載

主題瀏覽