Regulation of Actin dynamics by Formin in early Drosophila embryogenesis

by Zhiyi Lv
Doctoral thesis
Date of Examination:2014-12-18
Date of issue:2015-02-16
Advisor:Dr. Jörg Großhans
Referee:Dr. Jörg Grosshans
Referee:Dr. Reinhard Schuh
Persistent Address: http://dx.doi.org/10.53846/goediss-4879

 

 

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Abstract

English

During the development, cells have to change their shape, migrate and rearrange their internal structure properly etc. All these processes depend on actin cytoskeleton. In Drosophila embryonic development, the actin filaments form different structures corresponding to different developmental stages. The formin protein Dia, as an actin nucleator, plays an important role in the regulation of actin architecture. The F-BAR protein Cip4 overexpression leads to a phenocopy of dia in Drosophila embryos, implying the interaction of these two proteins. We found that in vitro Cip4 inhibited Dia activity by using actin pyrene and TIRF microscopy assay, collaborated with M. Winterhoff and Prof. Dr. J. Faix. dia mutant embryos show a defect on stabilization of membrane at furrow canals. I found that Arp2/3 complex promoted the membrane tubular extensions at furrow canals, and this effect was counteracted by Dia. Another phenotype of dia mutant is a defect of maintenance of membrane compartmentalization during cellularization. Using shibire/dynamin temperature sensitive allele, I found that sorting mechanism mediated by endocytosis and exocytosis was not essential for this process. By FRAP analysis, I could show that the difference of membrane mobility caused by F-actin accumulation contributes to the membrane compartmentalization. I propose that Dia localizes at furrow canals and polymerizes F-actin, and F-actin stabilizes the membrane at furrow canals and maintains the compartmentalization of lateral-basal domains. In addition, a new allele of ced-12 was identified. Current data suggest that Ced-12/Spg provides the signal linker between centrosomes and actin caps/metaphase furrows.
Keywords: Actin; Formin; Drosophila; Cellularization
 
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