神經系統主要的功能是傳遞訊息，會由神經元將訊息傳至周圍的細胞，而神經膠細胞則負責支持神經細胞及幫助神經細胞的分化。且在脊椎動物和無脊椎動物的神經系統中膠細胞能夠促進軸突的生成和包覆，使神經可以快速傳導神經衝動。此外，神經膠細胞也作為神經系統的主要免疫細胞，執行吞噬功能和清除死亡細胞以保護神經組織。各個種類的神經膠細胞在神經系統中執行了各種不同的功能。為了探討不同種類的膠細胞的發育與功能，本篇論文使用果蠅 (Drosophila melanogaster) 幼蟲的視覺系統作為模型，以研究不同種類的神經膠細胞的遷移及分化的過程中的交互作用。在發育過程中視網膜基底膠細胞 (retinal basal glia, RBG) 會經由連接大腦和眼盤 (eye disc)的視神經柄 (optic stalk) 遷移至眼盤。此時，眼盤後方的表皮細胞頂端 - 基底會收縮形成形態發生溝 (morphogenetic furrow, MF) 向前方移動依序分化成感光神經細胞 (Photoreceptor, PR)。神經膠細胞亦隨著感光神經細胞從後到前的方向移動分化。每個眼盤存在兩個像地毯一樣扁平的地毯膠細胞 (carpet glia, CG)，它的細胞膜會向著眼盤前端延伸，而細胞核則會停留在眼盤後端兩側。大部分的視網膜基底膠細胞會分佈在眼盤表面，故稱為表面膠細胞 (surface glia, SG)。當它們往前移動至地毯膠細胞膜前緣並接觸到感光神經細胞的軸突時會分化成包裹膠細胞 (wrapping glia, WG)。一般感光神經細胞的位置會以縱排列的方式依序由眼盤後端向前端分布在整個眼盤中，最前方的表面膠細胞會距離感光神經細胞的最前端約 3-5 排的感光神經細胞，而地毯膠細胞膜的最前緣則會距離最前端的表面膠細胞約 1-2 排感光神經細胞的距離。之前的文獻發現當地毯神經膠細胞被以凋亡基因抑制生長時，表面膠細胞會遷移到感光神經細胞的前方，該文獻因此提出地毯膠細胞的功能為調節表面膠細胞的移動，抑制表面膠細胞過早接觸感光神經細胞軸突。

為了探討果蠅幼蟲眼盤發育過程中，表面膠細胞分化成包裹膠細胞時的基因表現變化，我以不需要分離細胞，即可以找出特定細胞群內基因表現的標靶 DNA 腺嘌呤甲基轉移酶鑑定 (targeted DNA adenine methyl-transferase identification, targeted-DamID) 來找出表現在表面膠細胞和包裹膠細胞內的基因。以基因功能註解詞語分析表面膠細胞和包裹膠細胞內的基因時發現表面膠細胞內所表現的基因分別參與在肌動蛋白細胞骨架 (actin cytoskeleton)、細胞黏附分子 (cell adhesion molecules)和有絲分裂 (mitotic cytokinesis)的組織與發育過程中。另外，在包裹膠細胞內則有與軸突包裹及生長發育有關的基因表現，像是軸突簇生 (axonal fasciculation)、正調控細胞的生長 (positive regulation of growth)、調控細胞形狀 (regulation of cell shape)以及軸突導向 (axon guidance)。

另外，本論文也探討地毯膠細胞如何影響表面膠細胞在眼盤中的移動。實驗室先前已經以 targeted-DamID 找出地毯膠細胞內表現的基因，發現FGFR Breathless (Btl) 表現在地毯膠細胞。另外，細胞黏附分子組成單位 (integrin subunits) 也表現在地毯膠細胞內。FGFR Heartless (Htl) 先前已有文獻報導會調控表面膠細胞的移動和包裹膠細胞的分化，也表現在表面膠細胞內。為了研究地毯膠細胞是否透過 Btl 和 integrin subunits 影響表面膠細胞在眼盤中的移動，我以 UAS/Gal4 系統啟動核酸干擾技術 (RNA interference, RNAi) 降低 FGFR Btl 和 integrin subunits 在地毯膠細胞的表現，但並未發現這些基因的表現量下降後對地毯膠細胞的生長形態與表面膠細胞的移動有影響。

The main function of the nervous system is transmission of information. Neurons are responsible for transmission, and glial cells are responsible for supporting nerve cells and assisting the differentiation of neurons. The glial cells in the nervous system of vertebrates and invertebrates promote the formation and coating of axons, so that neurons can quickly produce impulses. In addition, glial cells also serve as the main immune cells of the nervous system, performing phagocytosis and eliminating dead cells. Each type of glial cell performs a variety of functions in the nervous system. I used the Drosophila larval eye disc as a model to study the interactions of different types of retinal basal glia (RBG). During development, RBGs migrate to the eye disc from the optic stalk, which connects the brain and eye disc. Cells in the posterior margin of the eye disc undergo an apical-basal contraction to form an indentation called the morphogenetic furrow (MF). Cells in the MF start to differentiate into photoreceptor cells (PRs). RBGs also gradually differentiate along with the differentiation PRs from the posterior to the anterior of the eye disc. Each eye disc has two carpet glial cells (CGs), which are flat as a carpet. The carpet glial membrane extends towards the front of the eye disc, while the cell nuclei stay on posterior sides of the eye disc. Most of the RBGs are on the surface of the eye disc, so they are called surface glia (SG). When they move forward, they contact PR axons and differentiate into wrapping glia (WG).

I used targeted DNA adenine methyl-transferase identification (targeted DamID-seq) to identify genes expressed in SGs and WGs. I found that SGs express genes regulating actin cytoskeleton, and also genes encoding cell adhesion molecules. I also found that WGs express genes involved in axonal fasciculation, positive regulation of growth, regulation of cell shape, and axon guidance. In addition, in order to explore how CGs affect the movement of SGs, I used the UAS/Gal4 system and RNA interference (RNAi) for knocking down expression of FGFR Breathless (Btl) and some integrin subunits in CGs. I found that reducing the expression of Btl and some integrin subunits in CGs has no effect on SG migration.

Abe, T., Yamazaki, D., Murakami, S., Hiroi, M., Nitta, Y., Maeyama, Y., & Tabata, T. (2014). The NAV2 homolog Sickie regulates F-actin-mediated axonal growth in Drosophila mushroom body neurons via the non-canonical Rac-Cofilin pathway. Development, 141(24), 4716-4728.
Adams, J. C., & Watt, F. M. (1993). Regulation of development and differentiation by the extracellular matrix. Development, 117(4), 1183-1198.
Ariss, M. M., Islam, A., Critcher, M., Zappia, M. P., & Frolov, M. V. (2018). Single cell RNA-sequencing identifies a metabolic aspect of apoptosis in Rbf mutant. Nat Commun, 9(1), 5024. doi:10.1038/s41467-018-07540-z
Ashburner, J., & Friston, K. J. (1999). Nonlinear spatial normalization using basis functions. Human brain mapping, 7(4), 254-266.
Awasaki, T., Tatsumi, R., Takahashi, K., Arai, K., Nakanishi, Y., Ueda, R., & Ito, K. (2006). Essential role of the apoptotic cell engulfment genes draper and ced-6 in programmed axon pruning during Drosophila metamorphosis. Neuron, 50(6), 855-867.
Bökel, C., & Brown, N. H. (2002). Integrins in development: moving on, responding to, and sticking to the extracellular matrix. Developmental cell, 3(3), 311-321.
Bahar, A. N., Habib, M. A., & Islam, M. M. (2013). Security architecture for mobile cloud computing. International Journal of Scientific Knowledge Computing and Information Technology, 3(3), 11-17.
Bainton, R. J., Tsai, L. T.-Y., Schwabe, T., DeSalvo, M., Gaul, U., & Heberlein, U. (2005). moody encodes two GPCRs that regulate cocaine behaviors and blood-brain barrier permeability in Drosophila. Cell, 123(1), 145-156.
Banerjee, S., Blauth, K., Peters, K., Rogers, S. L., Fanning, A. S., & Bhat, M. A. (2010). Drosophila neurexin IV interacts with Roundabout and is required for repulsive midline axon guidance. Journal of Neuroscience, 30(16), 5653-5667.
Barres, B. A. (2008). The mystery and magic of glia: a perspective on their roles in health and disease. Neuron, 60(3), 430-440.
Beiman, M., Shilo, B.-Z., & Volk, T. (1996). Heartless, a Drosophila FGF receptor homolog, is essential for cell migration and establishment of several mesodermal lineages. Genes & development, 10(23), 2993-3002.
Bjartmar, C., & Trapp, B. D. (2003). Axonal degeneration and progressive neurologic disability in multiple sclerosis. Neurotoxicity research, 5(1), 157-164.
Booth, G. E., Kinrade, E., & Hidalgo, A. (2000). Glia maintain follower neuron survival during Drosophila CNS development. Development, 127(2), 237-244.
Brand, A. H., & Perrimon, N. (1993). Targeted gene expression as a means of altering cell fates and generating dominant phenotypes. Development, 118(2), 401-415.
Cagan, R. L., & Ready, D. F. (1989). The emergence of order in the Drosophila pupal retina. Developmental biology, 136(2), 346-362.
Campbell, G., Goring, H., Lin, T., Spana, E., Andersson, S., Doe, C. Q., & Tomlinson, A. (1994). RK2, a glial-specific homeodomain protein required for embryonic nerve cord condensation and viability in Drosophila. Development, 120(10), 2957-2966.
Campos-Ortega, J. A., & Hartenstein, V. (1997). Stages of Drosophila embryogenesis. In The embryonic Development of Drosophila melanogaster (pp. 9-102): Springer.
Chen, J.-T., & Chang, W.-C. (2002). Effects of tissue culture conditions and explant characteristics on direct somatic embryogenesis in OncidiumGower Ramsey'. Plant cell, tissue and organ culture, 69(1), 41-44.
Chen, K.-F., & Crowther, D. C. (2012). Functional genomics in Drosophila models of human disease. Briefings in functional genomics, 11(5), 405-415.
Chen, Q., Lin, T. H., Der, C. J., & Juliano, R. (1996). Integrin-mediated activation of MEK and mitogen-activated protein kinase is independent of Ras. Journal of Biological Chemistry, 271(30), 18122-18127.
Choi, K.-W., & Benzer, S. (1994). Migration of glia along photoreceptor axons in the developing Drosophila eye. Neuron, 12(2), 423-431.
Clark, E. A., & Brugge, J. S. (1995). Integrins and signal transduction pathways: the road taken. Science, 268(5208), 233-239.
Clark, I. B., Muha, V., Klingseisen, A., Leptin, M., & Müller, H.-A. J. (2011). Fibroblast growth factor signalling controls successive cell behaviours during mesoderm layer formation in Drosophila. Development, 138(13), 2705-2715.
Cohen, S. M. (1993). Imaginal disc development. The development of Drosophila melanogaster, 747-841.
Delon, I., & Brown, N. H. (2007). Integrins and the actin cytoskeleton. Current opinion in cell biology, 19(1), 43-50.
DeSalvo, M. K., Hindle, S. J., Rusan, Z. M., Orng, S., Eddison, M., Halliwill, K., & Bainton, R. J. (2014). The Drosophila surface glia transcriptome: evolutionary conserved blood-brain barrier processes. Frontiers in neuroscience, 8, 346.
Du, L., Zhou, A., Patel, A., Rao, M., Anderson, K., & Roy, S. (2017). Unique patterns of organization and migration of FGF-expressing cells during Drosophila morphogenesis. Developmental biology, 427(1), 35-48.
Duménieu, M., Oulé, M., Kreutz, M. R., & Lopez-Rojas, J. (2017). The segregated expression of voltage-gated potassium and sodium channels in neuronal membranes: functional implications and regulatory mechanisms. Frontiers in Cellular Neuroscience, 11, 115.
Fernández-Moreno, M. A., Farr, C. L., Kaguni, L. S., & Garesse, R. (2007). Drosophila melanogaster as a model system to study mitochondrial biology. In Mitochondria (pp. 33-49): Springer.
Franzdóttir, S. R., Engelen, D., Yuva-Aydemir, Y., Schmidt, I., Aho, A., & Klämbt, C. (2009). Switch in FGF signalling initiates glial differentiation in the Drosophila eye. Nature, 460(7256), 758-761.
Freeman, M. R., & Doherty, J. (2006). Glial cell biology in Drosophila and vertebrates. Trends in neurosciences, 29(2), 82-90.
Freeman, W. J., Burke, B. C., & Holmes, M. D. (2003). Aperiodic phase re‐setting in scalp EEG of beta–gamma oscillations by state transitions at alpha–theta rates. Human brain mapping, 19(4), 248-272.
Garcia‐Bellido, A., & Merriam, J. R. (1969). Cell lineage of the imaginal discs in Drosophila gynandromorphs. Journal of Experimental Zoology, 170(1), 61-75.
Hacohen, N., Kramer, S., Sutherland, D., Hiromi, Y., & Krasnow, M. A. (1998). sprouty encodes a novel antagonist of FGF signaling that patterns apical branching of the Drosophila airways. Cell, 92(2), 253-263.
Halter, D. A., Urban, J., Rickert, C., Ner, S. S., Ito, K., Travers, A. A., & Technau, G. M. (1995). The homeobox gene repo is required for the differentiation and maintenance of glia function in the embryonic nervous system of Drosophila melanogaster. Development, 121(2), 317-332.
Ho, T.-Y., Wu, W.-H., Hung, S.-J., Liu, T., Lee, Y.-M., & Liu, Y.-H. (2019). Expressional profiling of carpet glia in the developing Drosophila eye reveals its molecular signature of morphology regulators. Frontiers in neuroscience, 13, 244.
Hosoya, T., Takizawa, K., Nitta, K., & Hotta, Y. (1995). glial cells missing: a binary switch between neuronal and glial determination in Drosophila. Cell, 82(6), 1025-1036.
Hummel, T., Attix, S., Gunning, D., & Zipursky, S. L. (2002). Temporal control of glial cell migration in the Drosophila eye requires gilgamesh, hedgehog, and eye specification genes. Neuron, 33(2), 193-203.
Ito, K., Urban, J., & Technau, G. M. (1995). Distribution, classification, and development of Drosophila glial cells in the late embryonic and early larval ventral nerve cord. Roux's archives of developmental biology, 204(5), 284-307.
Jones, B. W., Fetter, R. D., Tear, G., & Goodman, C. S. (1995). Glial cells missing: a genetic switch that controls glial versus neuronal fate. Cell, 82(6), 1013-1023.
Klambt, C. (1993). The Drosophila gene pointed encodes two ETS-like proteins which are involved in the development of the midline glial cells. Development, 117(1), 163-176.
Klämbt, C. (2009). Modes and regulation of glial migration in vertebrates and invertebrates. Nature Reviews Neuroscience, 10(11), 769-779.
Kumar, J. P. (2001). Signalling pathways in Drosophila and vertebrate retinal development. Nature Reviews Genetics, 2(11), 846-857.
Lawrence, P. A., & Struhl, G. (1996). Morphogens, compartments, and pattern: lessons from drosophila? Cell, 85(7), 951-961.
Limmer, S., Weiler, A., Volkenhoff, A., Babatz, F., & Klämbt, C. (2014). The Drosophila blood-brain barrier: development and function of a glial endothelium. Frontiers in neuroscience, 8, 365.
Lowe, N., Rees, J. S., Roote, J., Ryder, E., Armean, I. M., Johnson, G., . . . Magbanua, J. P. (2014). Analysis of the expression patterns, subcellular localisations and interaction partners of Drosophila proteins using a pigP protein trap library. Development, 141(20), 3994-4005.
Marshall, O. J., Southall, T. D., Cheetham, S. W., & Brand, A. H. (2016). Cell-type-specific profiling of protein–DNA interactions without cell isolation using targeted DamID with next-generation sequencing. Nature protocols, 11(9), 1586-1598.
McMahon, A., Reeves, G. T., Supatto, W., & Stathopoulos, A. (2010). Mesoderm migration in Drosophila is a multi-step process requiring FGF signaling and integrin activity. Development, 137(13), 2167-2175.
Mukherjee, T., Choi, I., & Banerjee, U. (2012). Genetic analysis of fibroblast growth factor signaling in the Drosophila eye. G3: Genes| Genomes| Genetics, 2(1), 23-28.
Murray, M. J., & Saint, R. (2007). Photoactivatable GFP resolves Drosophila mesoderm migration behaviour.
O'Reilly, A. M., Lee, H.-H., & Simon, M. A. (2008). Integrins control the positioning and proliferation of follicle stem cells in the Drosophila ovary. The Journal of cell biology, 182(4), 801-815.
Omel’yanchuk, L., Nokkala, C., Mattila, J., Lebedeva, L., Baimak, T. Y., & Akhmetova, K. (2007). The distribution of mitoses in the imaginal disks of third-instar Drosophila melanogaster larvae. Russian Journal of Genetics, 43(7), 769-775.
Rangarajan, R., Courvoisier, H., & Gaul, U. (2001). Dpp and Hedgehog mediate neuron–glia interactions in Drosophila eye development by promoting the proliferation and motility of subretinal glia. Mechanisms of development, 108(1-2), 93-103.
Rusnati, M., Tanghetti, E., Dell’Era, P., Gualandris, A., & Presta, M. (1997). αvβ3 integrin mediates the cell-adhesive capacity and biological activity of basic fibroblast growth factor (FGF-2) in cultured endothelial cells. Molecular Biology of the Cell, 8(12), 2449-2461.
Sato, M., & Kornberg, T. B. (2002). FGF is an essential mitogen and chemoattractant for the air sacs of the Drosophila tracheal system. Developmental cell, 3(2), 195-207.
Schlaepfer, D. D., Hanks, S. K., Hunter, T., & van der Geer, P. (1994). Integrin-mediated signal transduction linked to Ras pathway by GRB2 binding to focal adhesion kinase. Nature, 372(6508), 786-791.
Sieglitz, F., Matzat, T., Yuva-Aydemir, Y., Neuert, H., Altenhein, B., & Klämbt, C. (2013). Antagonistic feedback loops involving Rau and Sprouty in the Drosophila eye control neuronal and glial differentiation. Science signaling, 6(300), ra96-ra96.
Silies, M., Edenfeld, G., Engelen, D., Stork, T., & Klämbt, C. (2007). Development of the peripheral glial cells in Drosophila. Neuron glia biology, 3(1), 35-43.
Southall, T. D., Gold, K. S., Egger, B., Davidson, C. M., Caygill, E. E., Marshall, O. J., & Brand, A. H. (2013). Cell-type-specific profiling of gene expression and chromatin binding without cell isolation: assaying RNA Pol II occupancy in neural stem cells. Developmental cell, 26(1), 101-112.
Stork, T., Engelen, D., Krudewig, A., Silies, M., Bainton, R. J., & Klämbt, C. (2008). Organization and function of the blood–brain barrier in Drosophila. Journal of Neuroscience, 28(3), 587-597.
Tsao, C.-K., Ku, H.-Y., Lee, Y.-M., Huang, Y.-F., & Sun, Y. H. (2016). Long term ex vivo culture and live imaging of Drosophila larval imaginal discs. PloS one, 11(9), e0163744.
van Impel, A., Schumacher, S., Draga, M., Herz, H.-M., Großhans, J. r., & Müller, H. A. J. (2009). Regulation of the Rac GTPase pathway by the multifunctional Rho GEF Pebble is essential for mesoderm migration in the Drosophila gastrula.
Vicente-Manzanares, M., Choi, C. K., & Horwitz, A. R. (2009). Integrins in cell migration–the actin connection. Journal of cell science, 122(2), 199-206.
Wilson, D. P., Sutherland, C., Borman, M. A., Deng, J. T., MacDonald, J. A., & Walsh, M. P. (2005). Integrin-linked kinase is responsible for Ca2+-independent myosin diphosphorylation and contraction of vascular smooth muscle. Biochemical Journal, 392(3), 641-648.
Wolff, T. (1993). Pattern formation in the Drosophila retina. The development of Drosophila melanogaster, 1277-1325.
Xiong, W.-C., & Montell, C. (1995). Defective glia induce neuronal apoptosis in the repo visual system of Drosophila. Neuron, 14(3), 581-590.
Xiong, W.-C., Okano, H., Patel, N. H., Blendy, J. A., & Montell, C. (1994). repo encodes a glial-specific homeo domain protein required in the Drosophila nervous system. Genes & development, 8(8), 981-994.