The Smad genes play essential roles in body size regulation and male tail morphogenesis in Caenorhabditis elegans.
Item
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Title
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The Smad genes play essential roles in body size regulation and male tail morphogenesis in Caenorhabditis elegans.
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Identifier
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AAI3144149
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identifier
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3144149
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Creator
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Wang, Jianjun.
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Contributor
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Adviser: Cathy Savage-Dunn
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Date
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2004
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry | Biology, Molecular | Biology, Animal Physiology
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Abstract
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The Sma/Mab (TGF-beta) signaling pathway regulates the body size and male tail morphogenesis. The components include the ligand dbl-1, receptors daf-4 and sma-6, intracellular transducers sma-2, sma-3 and sma-4 (Smads). The mutants of the signaling pathway have small body size and male tail defects, fused sensory rays and crumpled spicules. It is suggested that the Smads cooperate in a heterotrimer manner to regulate the transcription of downstream target genes. The Smad proteins have highly conserved MH1 and MH2 domains connected by a linker region. The last two Serines of receptor responsive Smads are phosphorylated during the activation of the signaling. The crystal structures of mammalian Smads show the MH2 domain is critical for complex formation and receptor activation.;In C. elegans, the mechanism of Smad function is still poorly understood. In my studies, using the tissue specific expressed promoters, it is demonstrated that hypodermal expression of sma-3 is sufficient and necessary for body size rescue. It is supported by the similar experiment with sma-4 gene. Other groups also reported hypodermal expression of sma-6, daf-4, and lon-1 is critical for body size. And sma-3 expression in the seam cells rescues the body size also. The conclusion is going forward to that SMA-3 presence in hyp7 is crucial to rescue the body size. The C-terminal mutants of SMA-3 are dominant negative in body size, but they are functional in male tail sensory rays. Pseudophosphorylated SMA-2 is constitutively active in body size rescuing suggests that the phosphorylated SMA-3 plays essential roles in the functional complex. According to all of the combination of different phosphorylated states of SMA-2 and SMA-3, it is suggested that two different kinds of trimers have distinct roles in worm development.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
