肝醣生成酵素激酶-3β對斑馬魚血管發育的影響

Abstract

肝醣生成酵素激酶(Glycogen synthase kinase-3β; GSK3β)是參與在Wnt/β-catenin signaling pathway中非常重要的調控因子，對於細胞分化及軸向發育都十分的重要。雖然在許多細胞培養的實驗當中都顯示GSK3β能調控小血管的新生(angiogenesis)，然而在胚胎時期中GSK3β對於血管發育的影響及分子機制仍然不清楚。為了回答這個問題，我們利用基因抑制劑(morpholino antisense oligonucleiotides；MO) 注射到一細胞時期血管綠螢光的基因轉殖魚Tg(fli1:EGFP) 來抑制GSK3β的表現，再藉由觀察基因轉殖魚的綠螢光血管探討GSK3β對血管發育的影響。在28hpf時觀察MO注射的個體intersegmental vessels (ISV) 較短且無法延伸至背部形成dorsal longitudinal vessels (DLAV)，在48-72 hpf ISV依然不完整且生長也失去方向性而parachordal vessels (PAV)的生長也受到影響。Sub-intestinal venous vessels (SIV)也無法正常發育，甚至完全消失，而尾部的venous plexus也變得較膨大。此外，尾鰭部份的微血管叢也完全無法生長。因此我們認為GSK3β確實能調控血管的發育。然而注射MO的個體中動脈(deltaC, notch3)、靜脈(flt4, ephb4)專一基因的mRNA表現與對照組卻沒有顯著的差異，暗示著動靜脈的分化似乎不受影響。此外觀察體節雖然能形成但myod卻異位性地表現在somite boundary。總結以上幾點，我們認為GSK3β確實能調控angiogenesis但不影響vasculogenesis。此外，ISV的缺失可能是由於體節缺失所造成的。

Glycogen synthase kinase-3β (GSK3β) is involved in the canonical Wnt/β-catenin signaling pathway and essential for cell differentiation and axis formation. Although many in vitro researches indicated GSK3β may modulate the angiogenesis, the molecular mechanism of GSK3β that plays roles on vascular development in embryonic development remains unknown. To address this issue, we microinjected the morpholino antisense oligonucleiotides (MOs) which specifically inhibits the translation of GSK3β into the one-celled embryos derived from the fli1:EGFP transgenic zebrafish expressing GFP in all blood vessels. At 28-hpf, the gsk3β morphants exhibited shorten intersegmental vessels (ISV) and the discontinued dorsal longitudinal vessels (DLAV). At 48-72 hpf, the ISV remained a shortened form and even disoriented migration and the sub-intestinal venous vessels (SIVs) were reduced or even completely lost. The venous plexus became less complex compared to control embryos. Moreover, the capillary of tail fin were all defective. We propose GSK3β plays important roles in angiogenesis of zebrafish. Unexpectedly, the patterns showing by the artery specific (deltaC, notch3) and the venous specific (flt4, ephb4) markers in gsk3β morphants were indistinguishable from those of control embryos, suggesting the artery-venous differentiation was unperturbed. Although the somite boundary still existed, myod was ectopically expressed in somite boundary in gsk3β morphants. Taken together, these results indicate GSK3β functions in angiogenesis, but not in vasculogenesis. Furthermore, the ISV defect in trunk may be due to somite malformation and vessel defect.