DGIST Scholar: Early sensory-experience modulates pheromone-mediated behaviors of adult C. elegans

Department of Brain Sciences Theses Ph.D.

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Early sensory-experience modulates pheromone-mediated behaviors of adult C. elegans

Title: Early sensory-experience modulates pheromone-mediated behaviors of adult C. elegans

Alternative Title: 페로몬 감각 각인의 기초가 되는 회로 메커니즘연구

Author(s): Hong, Myeongjin

Advisor: Kim, Kyu Hyung

Co-Advisor(s): Kea Joo Lee

Issued Date: 2018

Awarded Date: 2018. 2

Type: Thesis

Subject: Neuroconnectome ; Synaptic plasticity ; Imprinting ; Molecular genetics ; 뉴로커넥톰 ; 각인 ; 시냅스

Abstract: Experiences during early development can influence neuronal functions and modu-late adult behaviors. However, the molecular mechanisms underlying the long-term be-havioral effects of these early experiences are not fully understood. The C. elegans ascr#3 pheromone triggers avoidance behavior in adult hermaphrodites.

Here, I show that hermaphrodites that are briefly exposed to ascr#3 immediately af-ter birth exhibit increased ascr#3-specific avoidance as adults indicating that ascr#3-experienced animals form a long lasting memory or imprint of this early ascr#3 exposure. ascr#3 imprinting is mediated by increased synaptic activity between the ascr#3-sensing ADL neurons and their post-synaptic SMB motor neuron partners via increased expression of the odr-2 GPI-linked signaling and avr-14 glutamate-gated chloride channel genes in the SMB neurons.

My study suggests that the memory for early ascr#3 experience is imprinted via al-teration of a single synaptic connection, that in turn shapes experience-dependent plastici-ty in adult ascr#3 responses.
ⓒ 2017 DGIST

Table Of Contents: Ⅰ. Introduction 1--

1.1 Neuroconnectome 1--

1.2 Synaptic plasticity 1--

1.3 Studying of C. elegans as a model system 2--

1.4 C. elegans pheromones 3--

1.5 Early pheromone-experienced study of C. elegans 4--

II. Experimental Method & Materials 5--

2.1 Experimental Model and Subject Details 5--

2.2 Method Details 5--

2.2.1 Generation of C. elegans transgenic lines 5--

2.2.2 Pheromone imprinting 6--

2.2.3 Post-dauer assay 7--

2.2.4 Behavioral assay 7--

2.2.5 In vivo calcium imaging 8--

2.2.6 Levamizole treatment 8--

2.2.7 Heat shock treatment 9--

2.3 Quantification and Statistical Analysis 9--

2.3.1 Representative images 9--

2.3.2 GFP quantification 9--

2.3.3 Statistical tests 10--

III. Result 11--

3.1 Adult C. elegans transiently exposed to ascr#3 during larval stages ex-hibits increased acsr#3 pheromone avoidance 11--

3.1.1 Pheromone imprinting assay of naive and pre-exposed worms 11--

3.1.2 Optimal ascr#3 concentration of pre-exposure effect 13--

3.1.3 Early ascr#3 experience of males 14--

3.2 The memory for ascr#3 is acquired during the L1 larval stage 14--

3.2.1 ascr#3 imprinting is L1 specific 14--

3.2.2 The critical time for imprinting of L1 stage 15--

3.2.3 ascr#3 imprinting is pheromone specific 16--

4.1 odr-2 Acts in the SMB neurons to increase ascr#3 avoidance in ascr#3-imprinted animals 20--

4.1.1 Candidate gene search 20--

4.1.2 odr-2 recue study 22--

4.1.3 SMB sensory/inter/motor neurons 24--

4.1.4 Association of SMB and Imprining 25--

4.2 ascr#3-induced responses in the ADL chemosensory neurons are unal-tered in ascr#3 imprinted worms 25--

4.2.1 ADL Ca²⁺ Imaging 25--

4.2.2 ADL Ca²⁺ Imaging in odr-2 27--

4.2.3 AIB, AVD, AVA Ca²⁺ imaging 27--

4.3 SMB mediates increased ascr#3 avoidance in ascr#3 imprinted ani-mals 30--

4.3.1 SMB Ca²⁺ Imaging 30--

4.3.2 Levamisole-treated SMB Ca²⁺ Imaging 31--

4.3.3 ADLp::TeTx-treated SMB Ca²⁺ Imaging 32--

4.3.4 SMB Ca²⁺ Imaging in odr-2 34--

4.4 Upregulation of odr-2 expression in SMB of ascr#3-imprinted L1 lar-vae is sufficient for ascr#3 imprinting 34--

4.4.1 GFP quantification of naive and imprinted C. elegans 34--

4.4.2 Heatshock study of non-imprinted animals 35--

4.4.3 avr-14 study 36--

IV. Discussion 38--

V. Conclusion 40