葉酸是胚胎發育必需的營養素。懷孕婦女未能攝取充足的葉酸將會增加其胎兒獲得先天性神經管缺陷的風險。然而對於葉酸缺乏造成的出生缺陷的作用機轉還未完全了解。斑馬魚是一個研究發育生物學有利的動物模式，但是要利用控制魚的飲食來造成葉酸缺乏卻極其困難。在本研究中利用熱休克啟動子控制γ-穀氨酸水解酶的異位表達，建立一誘發性葉酸缺乏斑馬魚動物模式。γ-穀氨酸水解酶的功能是藉由去除葉酸結構上鍵結的多穀氨酸來促進細胞內葉酸的運送。我們發現在此動物模式中葉酸缺乏的嚴重程度和γ-穀氨酸水解酶的表現量呈正相關。且葉酸缺乏的斑馬魚胚胎展現了臨床相關疾病特徵，包括:異常的神經管閉合、頭臉部及眼睛的發育異常和受損的造血功能。這些發育缺陷藉由補充葉酸都能夠部分恢復，顯示葉酸缺乏造成疾病產生的因果特異性。我們也發現在葉酸缺乏的胚胎中神經細胞和後側線基原細胞的正常遷移受到阻擾，進一步探討顯示氧化壓力和細胞外訊號調節激酶的訊號路徑很可能參與在葉酸缺乏導致的先天性異常。以上的結果顯示此新發展出的動物模式能提供做為另一實驗脊椎動物平台應用於活體研究葉酸缺乏相關致病機轉。

Folate is an essential nutrient, which is especially important for embryogenesis. Insufficient folate intake in pregnant women was reported to increase the risk of delivering the fetus with congenital defects including neural tube defects. However, the etiology for folate deficiency-associated birth defects is not fully understood. Zebrafish is a powerful model organism for developmental biology research. However, to establish a folate deficient zebrafish via dietary control is difficult and impractical. In present study, we established a heat-shock induced folate deficient zebrafish model by ectopically expressing γ–glutamyl hydrolase (GGH), the enzyme removing the polyglutamyl moiety of folate and facilitating the exportation of intracellular folate. We found that the extent of folate deficiency in GGH-overexpressing transgenic embryos was positively correlated to the expression level of GGH. These folate deficient embryos exhibited the characteristic phenotypes of folate deficiency, including impeded neural tube closure, craniofacial and ophthalmic abnormalities and impaired hematopoiesis. These anomalies were partly reversed by folate supplementation, suggesting a cause-and-consequence specificity. Our results also showed that the migration of neural crest cells and posterior lateral line primordia were obstructed in folate deficient transgenic embryos. Further investigation suggested that oxidative stress and ERK signal pathway were likely to be involved in the occurrence of abnormalities caused by folate deficiency. Our results suggested that this newly developed model can serve an alternative platform of vertebrate for studying folate-deficiency associated pathogenesis in vivo.

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