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Title:Using Xenopus laevis to study the mechanisms governing the early germline development and the formation of vertebrate body plan
Author(s):Fu, Jia
Advisor(s):Yang, Jing
Contributor(s):Bagchi, Indrani C; Spinella, Michael J; Chen, Jie
Department / Program:Comparative Biosciences
Discipline:VMS - Comparative Biosciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Germ plasm
RTK signaling
Xenopus Laevis
Abstract:In animals like Drosophila, C. elegans, zebrafish and Xenopus, the primordial germ cells (PGC), the precursors of the gametes, are specified through the inheritance of germ plasm. Early PGC development is regulated by the genetic program coded by unique maternal factors in the germ plasm. However, the biological functions of these germ plasm components and their molecular mechanisms are poorly understood. We found that Dzip1 (Daz-interacting protein1) is a novel component of germ plasm in Xenopus oocytes and embryos. The loss-of-function analysis showed that Dzip1 regulates the first wave of PGC proliferation. Overexpression of Dzip1 and Xvelo stabilize each other in the germ plasm during oocyte maturation. In vitro analysis suggests that Dzip1 decreases the solubility of Xvelo and induces Xvelo to form aggregates in the cytoplasm. Therefore we argue that Dzip1, by interacting and stabilizing Xvelo, regulates the integrity of germ plasm. In addition, our results reveal that Dzip1, by interacting with Dazl (Deleted in Azoospermia-like), controls the development of PGC in early embryos. Disrupting the physical interaction between Dzip1 and Dazl results in reduction of PGCs. Collectively, we defined the roles of Dzip1 on early germline development in Xenopus. Receptor tyrosine kinase (RTK) signaling is used repeatedly during Xenopus embryogenesis to establish the body plan. Ligand-independent activation of RTKs allows dissecting the receptor-specific signaling outcomes from the pleiotropic effects of the ligands. In this regard, RTK intracellular domains (ICDs) are of interest due to their ability to recapitulate signaling activity in a ligand-independent manner when fused to chemical and optical dimerizing domains. A common strategy for synthetic activation of RTKs involves membrane tethering of dimerizer-RTK ICD fusions. Depending on the intrinsic signaling capacity, however, this approach could entail undesirable baseline signaling activity in the absence of stimulus, thereby diminishing the system's sensitivity. To surpass this challenge, we developed a cytoplasm-to-membrane translocation approach, where FGFR ICD is recruited from the cytoplasm to the plasma membrane by light, leading to its subsequent activation. This strategy results in optical activation of FGFR with low background activity and high sensitivity, which allows light-induced formation of ectopic tail-like structure in developing embryos. We further generalized this strategy by developing optogenetic platforms to control three neurotrophic tropomyosin receptor kinases, TrkA, TrkB, and TrkC. We envision that these ligand-independent optogenetic RTKs will provide useful toolsets that allow for the delineation of signaling subcircuits in developing vertebrate embryos.
Issue Date:2020-07-08
Rights Information:Copyright 2020 Jia Fu
Date Available in IDEALS:2020-10-07
Date Deposited:2020-08

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