{"id":{"repo_id":"tamu","oai_identifier":"oai:oaktrust.library.tamu.edu:1969.1/174557"},"canonical_url":"https://search.dev.ndltd.org/etd/tamu/oai:oaktrust.library.tamu.edu:1969.1/174557","repository":{"repo_id":"tamu","name":"Texas A&M University","base_url":"https://oaktrust.library.tamu.edu/server/oai/request"},"display":{"title":"Regulation of the Ras Signaling Network in C. Elegans Development","abstract":"An EGF gradient induces the equipotent C. elegans vulval precursor cells (VPCs) to assume the 3˚-3˚-2˚-1˚-2˚-3˚ pattern of cell fates. EGF triggers the LET-60/Ras-LIN-45/Raf-MEK-2/MEK-MPK-1/ERK canonical MAP kinase cascade to induce 1˚ fate and synthesize of DSL ligands for the lateral Notch signal. In turn, LIN-12/Notch induces neighboring cells to become 2˚. In response to lower dose of EGF signal, LET-60/Ras switches effectors to use the RGL-1/RalGEF-RAL-1/Ral modulatory signaling cascade to promote 2˚ fate in support of LIN-12. The goals of this research are to define principles by which signaling networks function and to identify an effector cascade downstream of RAL-1. RAL-1 signals through EXOC-8/Exo84, an established Ral binding partner, GCK-2, a CNH domain-containing MAP4 Kinase, and PMK-1/p38 MAP kinase to promote 2˚ fate. We also show that RGL-1 plays opposing and genetically separable roles in VPC fate patterning. RGL-1 promotes 2˚ fate via canonical GEF-dependent activation of RAL-1 and 1˚ fate via a non-canonical GEF-independent activity. Our genetic epistasis experiments are consistent with RGL-1 functioning in the modulatory 1˚-promoting AGE-1/PI3-Kinase-PDK-1/PDK-AKT-1/Akt cascade. Animals without RGL-1 experience 15-fold higher rates of VPC patterning errors compared to the wild type. Yet VPC patterning in RGL-1 deletion mutants is not more sensitive to environmental perturbations. We propose that RGL-1 functions as a “Balanced Switch” that orchestrates opposing 1˚- and 2˚-promoting modulatory cascades to decrease developmental stochasticity. To investigate how LET-60/Ras switches effectors to promote different cell fates, we used CRISPR to tag endogenous LIN-45/Raf and RGL-1/RalGEF proteins. We found that they are recruited to different subcellular compartments during VPC induction. LIN-45 is recruited to the basolateral membrane in presumptive 1˚ cells. RGL-1 is recruited to the apical membrane in presumptive 2˚ cells, and this localization depends on functional LET-60. We hypothesize that RGL-1 apical localization in the VPCs is mediated by phosphorylation or scaffold proteins. Our studies delineate a novel Ral-dependent developmental signaling cascade, bifunctional RGL-1 as a “Balanced Switch”, and LET-60 effector segregation mechanism in vivo, thus providing critical insights for understanding Ras biology in cancer and development.","abstract_html":"An EGF gradient induces the equipotent C. elegans vulval precursor cells (VPCs) to assume the 3˚-3˚-2˚-1˚-2˚-3˚ pattern of cell fates. EGF triggers the LET-60/Ras-LIN-45/Raf-MEK-2/MEK-MPK-1/ERK canonical MAP kinase cascade to induce 1˚ fate and synthesize of DSL ligands for the lateral Notch signal. In turn, LIN-12/Notch induces neighboring cells to become 2˚. In response to lower dose of EGF signal, LET-60/Ras switches effectors to use the RGL-1/RalGEF-RAL-1/Ral modulatory signaling cascade to promote 2˚ fate in support of LIN-12. The goals of this research are to define principles by which signaling networks function and to identify an effector cascade downstream of RAL-1. RAL-1 signals through EXOC-8/Exo84, an established Ral binding partner, GCK-2, a CNH domain-containing MAP4 Kinase, and PMK-1/p38 MAP kinase to promote 2˚ fate. We also show that RGL-1 plays opposing and genetically separable roles in VPC fate patterning. RGL-1 promotes 2˚ fate via canonical GEF-dependent activation of RAL-1 and 1˚ fate via a non-canonical GEF-independent activity. Our genetic epistasis experiments are consistent with RGL-1 functioning in the modulatory 1˚-promoting AGE-1/PI3-Kinase-PDK-1/PDK-AKT-1/Akt cascade. Animals without RGL-1 experience 15-fold higher rates of VPC patterning errors compared to the wild type. Yet VPC patterning in RGL-1 deletion mutants is not more sensitive to environmental perturbations. We propose that RGL-1 functions as a “Balanced Switch” that orchestrates opposing 1˚- and 2˚-promoting modulatory cascades to decrease developmental stochasticity. To investigate how LET-60/Ras switches effectors to promote different cell fates, we used CRISPR to tag endogenous LIN-45/Raf and RGL-1/RalGEF proteins. We found that they are recruited to different subcellular compartments during VPC induction. LIN-45 is recruited to the basolateral membrane in presumptive 1˚ cells. RGL-1 is recruited to the apical membrane in presumptive 2˚ cells, and this localization depends on functional LET-60. We hypothesize that RGL-1 apical localization in the VPCs is mediated by phosphorylation or scaffold proteins. Our studies delineate a novel Ral-dependent developmental signaling cascade, bifunctional RGL-1 as a “Balanced Switch”, and LET-60 effector segregation mechanism in vivo, thus providing critical insights for understanding Ras biology in cancer and development.","abstract_has_math":false,"creators":["Shin, Hanna"],"institution":"Texas A & M University","degree_name":"Doctor of Philosophy","degree_level":"Doctoral","degree_discipline":"Medical Sciences","degree_department":null,"school":null,"contributors":[],"advisors":["Reiner, David J"],"committee_chairs":[],"committee_members":["Davies, Peter","Zhou, Yubin","Arur, Swathi","Frost, Jeffrey A"],"year":2018,"date_issued":"2018-11-07","date_published":"2018-11-07","updated_at":"2026-08-21T16:48:40Z","subjects":["C. elegans","Ras","LET-60","Ral","RAL-1","GCK-2","MAP4K","Exo84","EXOC-8","PMK-1","p38","RGL-1","RalGEF","VPC fate patterning","development","effector","Raf","LIN-45"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1969.1/174557","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"source_record":{"url":"https://oaktrust.library.tamu.edu/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aoaktrust.library.tamu.edu%3A1969.1%2F174557","prefix":"dim"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Reiner, David J"]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Davies, Peter","Zhou, Yubin","Arur, Swathi","Frost, Jeffrey A"]},{"key":"dc:creator","label":"Author","values":["Shin, Hanna"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2019-01-23T21:11:56Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2020-12-01T07:33:14Z"]},{"key":"dc:date.issued","label":"Date","values":["2018-11-07"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Medical Sciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Texas A & M University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["C. elegans","Ras","LET-60","Ral","RAL-1","GCK-2","MAP4K","Exo84","EXOC-8","PMK-1","p38","RGL-1","RalGEF","VPC fate patterning","development","effector","Raf","LIN-45"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/1969.1/174557"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["An EGF gradient induces the equipotent C. elegans vulval precursor cells (VPCs) to assume the 3˚-3˚-2˚-1˚-2˚-3˚ pattern of cell fates. EGF triggers the LET-60/Ras-LIN-45/Raf-MEK-2/MEK-MPK-1/ERK canonical MAP kinase cascade to induce 1˚ fate and synthesize of DSL ligands for the lateral Notch signal. In turn, LIN-12/Notch induces neighboring cells to become 2˚. In response to lower dose of EGF signal, LET-60/Ras switches effectors to use the RGL-1/RalGEF-RAL-1/Ral modulatory signaling cascade to promote 2˚ fate in support of LIN-12. The goals of this research are to define principles by which signaling networks function and to identify an effector cascade downstream of RAL-1. RAL-1 signals through EXOC-8/Exo84, an established Ral binding partner, GCK-2, a CNH domain-containing MAP4 Kinase, and PMK-1/p38 MAP kinase to promote 2˚ fate. We also show that RGL-1 plays opposing and genetically separable roles in VPC fate patterning. RGL-1 promotes 2˚ fate via canonical GEF-dependent activation of RAL-1 and 1˚ fate via a non-canonical GEF-independent activity. Our genetic epistasis experiments are consistent with RGL-1 functioning in the modulatory 1˚-promoting AGE-1/PI3-Kinase-PDK-1/PDK-AKT-1/Akt cascade. Animals without RGL-1 experience 15-fold higher rates of VPC patterning errors compared to the wild type. Yet VPC patterning in RGL-1 deletion mutants is not more sensitive to environmental perturbations. We propose that RGL-1 functions as a “Balanced Switch” that orchestrates opposing 1˚- and 2˚-promoting modulatory cascades to decrease developmental stochasticity. To investigate how LET-60/Ras switches effectors to promote different cell fates, we used CRISPR to tag endogenous LIN-45/Raf and RGL-1/RalGEF proteins. We found that they are recruited to different subcellular compartments during VPC induction. LIN-45 is recruited to the basolateral membrane in presumptive 1˚ cells. RGL-1 is recruited to the apical membrane in presumptive 2˚ cells, and this localization depends on functional LET-60. We hypothesize that RGL-1 apical localization in the VPCs is mediated by phosphorylation or scaffold proteins. Our studies delineate a novel Ral-dependent developmental signaling cascade, bifunctional RGL-1 as a “Balanced Switch”, and LET-60 effector segregation mechanism in vivo, thus providing critical insights for understanding Ras biology in cancer and development."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Regulation of the Ras Signaling Network in C. Elegans Development"]}]}],"canonical_facts":{"dc:contributor.advisor":["Reiner, David J"],"dc:contributor.committeemember":["Davies, Peter","Zhou, Yubin","Arur, Swathi","Frost, Jeffrey A"],"dc:creator":["Shin, Hanna"],"dc:date.accessioned":["2019-01-23T21:11:56Z"],"dc:date.available":["2020-12-01T07:33:14Z"],"dc:date.issued":["2018-11-07"],"dc:description.abstract":["An EGF gradient induces the equipotent C. elegans vulval precursor cells (VPCs) to assume the 3˚-3˚-2˚-1˚-2˚-3˚ pattern of cell fates. EGF triggers the LET-60/Ras-LIN-45/Raf-MEK-2/MEK-MPK-1/ERK canonical MAP kinase cascade to induce 1˚ fate and synthesize of DSL ligands for the lateral Notch signal. In turn, LIN-12/Notch induces neighboring cells to become 2˚. In response to lower dose of EGF signal, LET-60/Ras switches effectors to use the RGL-1/RalGEF-RAL-1/Ral modulatory signaling cascade to promote 2˚ fate in support of LIN-12. The goals of this research are to define principles by which signaling networks function and to identify an effector cascade downstream of RAL-1. RAL-1 signals through EXOC-8/Exo84, an established Ral binding partner, GCK-2, a CNH domain-containing MAP4 Kinase, and PMK-1/p38 MAP kinase to promote 2˚ fate. We also show that RGL-1 plays opposing and genetically separable roles in VPC fate patterning. RGL-1 promotes 2˚ fate via canonical GEF-dependent activation of RAL-1 and 1˚ fate via a non-canonical GEF-independent activity. Our genetic epistasis experiments are consistent with RGL-1 functioning in the modulatory 1˚-promoting AGE-1/PI3-Kinase-PDK-1/PDK-AKT-1/Akt cascade. Animals without RGL-1 experience 15-fold higher rates of VPC patterning errors compared to the wild type. Yet VPC patterning in RGL-1 deletion mutants is not more sensitive to environmental perturbations. We propose that RGL-1 functions as a “Balanced Switch” that orchestrates opposing 1˚- and 2˚-promoting modulatory cascades to decrease developmental stochasticity. To investigate how LET-60/Ras switches effectors to promote different cell fates, we used CRISPR to tag endogenous LIN-45/Raf and RGL-1/RalGEF proteins. We found that they are recruited to different subcellular compartments during VPC induction. LIN-45 is recruited to the basolateral membrane in presumptive 1˚ cells. RGL-1 is recruited to the apical membrane in presumptive 2˚ cells, and this localization depends on functional LET-60. We hypothesize that RGL-1 apical localization in the VPCs is mediated by phosphorylation or scaffold proteins. Our studies delineate a novel Ral-dependent developmental signaling cascade, bifunctional RGL-1 as a “Balanced Switch”, and LET-60 effector segregation mechanism in vivo, thus providing critical insights for understanding Ras biology in cancer and development."],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["https://hdl.handle.net/1969.1/174557"],"dc:language.iso":["en"],"dc:subject":["C. elegans","Ras","LET-60","Ral","RAL-1","GCK-2","MAP4K","Exo84","EXOC-8","PMK-1","p38","RGL-1","RalGEF","VPC fate patterning","development","effector","Raf","LIN-45"],"dc:title":["Regulation of the Ras Signaling Network in C. Elegans Development"],"dc:type":["Thesis"],"thesis:degree_discipline":["Medical Sciences"],"thesis:degree_level":["Doctoral"],"thesis:degree_name":["Doctor of Philosophy"],"thesis:institution_name":["Texas A & M University"]},"updated_at":"2026-08-21T16:48:40Z"}