探討Zfp280d在PDX1所調控的胰臟發育中所扮演的角色

近年來胰臟發育的研究已經可以將相關的轉錄因子(transcription factor) 描繪成一個網絡系統，包括了PDX1、Ptf1a以及Ngn3等。在這些轉錄因子當中，PDX1具有能夠決定內胚層中原腸腔 (primitive gut) 發育成胰臟的區域的能力，因此PDX1基因缺陷小鼠往往不會有胰臟的發育。此外也有研究顯示，PDX1對於β-cell的功能維持是相當重要的。為了更進一步研究PDX1在胰臟發育時期的功能，我們實驗室利用酵母菌雙雜交系統 (yeast two-hybrid assay) 尋找10.5天的胚胎胰臟芽基因庫(E10.5 pancreatic bud cDNA library) 中能夠與PDX1有交互作用的蛋白質。我們成功地篩選出許多基因，包括了尚未被研究過的鋅模組蛋白Zinc finger protein 280d (Zfp280d)。分析這個蛋白質的胺基酸序列，發現它含有九個Zinc finger domain，而我們利用酵母菌雙雜交系統篩出的片段中，有一個保守性但功能未知的DUF4195序列。在我的研究中，我已經成功的利用證實PDX1與Zfp280d有直接交互作用，並且可以推定Zfp280d是透過DUF4195 domain 跟PDX1做結合。隨後，我利用共免疫沉澱分析 (co-immunoprecipitation) 證實了在哺乳動物細胞中PDX1-Zfp280d的交互作用也是存在的。進一步做共免疫螢光染色(co-immunofluroence)，我也發現在細胞中表現的PDX1與Zfp280d有共同在坐落在細胞核中的情形。另一方面，根據gene reporter assay的實驗結果，初步發現PDX1的下游基因insulin的活性會因共表現了Zfp280d而有減弱的現象。這些結果一再的顯示Zfp280d在胰臟早期發育和β-cell功能維持上扮演了一個相當重要的角色。在未來，我們會藉由小鼠肝細胞株BNL的轉分化過程以及在小鼠 β-cell line NIT-1中減弱或增強Zfp280d的表現量，分析胰臟相關基因的表現量變化，即可找出Zfp280d在胰臟發育時期所扮演的生理功能為何。

關鍵字

發育；胰臟； Zfp280d ； PDX1

並列摘要

Recent studies have identified a network of transcription factors that are important for the development of pancreas, including PDX1, Ptf1a and Ngn3. Among these factors, PDX1 plays a critical role in defining the region of the primitive gut that will form the pancreas; as a result, PDX1-deficient mice fail to develop pancreatic tissue. Besides, it has been shown that PDX1 is also important for proper β-cell function and maintenance. To further understand the action of PDX1, we have utilized the yeast two-hybrid assay to screen an E10.5 pancreatic bud cDNA library using PDX1 as a bait. Several genes are identified from the screening, including zinc finger protein 280d (Zfp280d) whose function has not been described before. Judged from its protein sequence, Zfp280d contains nine zinc finger domains. In addition, the sequence (Zfp280dΔ, aa. 46-272) which was identified by the yeast two-hybrid assay encodes a conserve domain called DUF4195 with unknown function. In my study, I have shown that Zfp280d and PDX1 physically interact and that the DUF4195 domain of Zfp280d is the putative binding region for this interaction. Subsequently, I have also proved that the PDX1-Zfp280d interaction exists in mammalian cells by performing co-immunoprecipitation (Co-IP). Besides, through double immunofluorescence staining, I have shown that both transiently expressed PDX1 and Zfp280d are co-localized in the nucleus. On the other hand, by performing gene reporter assays, I have found that the expression of PDX1’s downstream gene is suppressed when Zfp280d is co-expressed with PDX1 in 293T. These results suggest that Zfp280d may play a role in regulating early pancreas development and β-cell function. In the future, knock-down and over-expression of Zfp280d will be performed in cell lines, including NIT-1 (mice β-cell line) and BNL (liver cell line) to further study the biological functions of Zfp280d.

並列關鍵字

development ； pancreas ； Zfp280d ； PDX1

參考文獻

Aasland, R., Gibson, T.J., and Stewart, A.F. (1995). The PHD finger: implications for chromatin-mediated transcriptional regulation. Trends in biochemical sciences 20, 56-59.

Ahlgren, U., Jonsson, J., Jonsson, L., Simu, K., and Edlund, H. (1998). beta-cell-specific inactivation of the mouse Ipf1/f1 gene results in loss of the beta-cell phenotype and maturity onset diabetes. Genes & development 12, 1763-1768.

Babu, D.A., Deering, T.G., and Mirmira, R.G. (2007). A feat of metabolic proportions: Pdx1 orchestrates islet development and function in the maintenance of glucose homeostasis. Molecular genetics and metabolism 92, 43-55.

Bock, P., Abdel-Moneim, M., and Egerbacher, M. (1997). Development of pancreas. Microscopy research and technique 37, 374-383.

Boitard, C. (2012). Pancreatic islet autoimmunity. Presse Med 41, e636-650.

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探討Zfp280d在PDX1所調控的胰臟發育中所扮演的角色

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