Rumi is a protein O-glucosyltransferase that adds the sugar O-glucose onto the serine in the target sequence C-S-X-S-(P/A)-C found within properly folded EGF repeats. It was first discovered to modify the Drosophila Notch extracellular domain and to be required for Notch signaling in a temperature dependent manner, but other targets of Rumi remained unknown. Several other proteins in the Drosophila proteome harbor multiple consensus sequence highly predictive of O-glucose, including the transmembrane protein Crumbs and the secreted protein Eyes shut (Eys). Both of these proteins are required for proper eye development and mutations in their human homologs cause a blindness disorder named retinitis pigmentosa. Therefore, we sought to determine whether Rumi plays a role in photoreceptor development. We found that rumi–/– animals have defects in photoreceptor spacing in which many neighboring rhabdomeres are attached. This phenotype cannot be explained by the loss of O-glucose on Notch or Crumbs. However, eys genetically interacts with rumi, and in rumi–/– animals at the start of rhabdomere separation, Eys accumulates intracellularly and decreased levels of Eys reach the extracellular space. Overexpressing a mutant Eys transgene which contains no intact O-glucosylation sites also results in intracellular accumulation of Eys, suggesting that loss of O-glucose from Eys is the cause. Additionally, both the intracellular accumulation and the rhabdomere attachment defect grow more severe at higher temperatures, and Eys degrades at higher temperatures in rumi–/–. In addition, removing one copy of the chaperone Hsc70-3 enhances the rumi–/– phenotype. Together, these data suggest that loss of O-glucose from Eys causes a defect in its proper folding, which leads to decreased Eys reaching the extracellular space and therefore a failure in full separation of the rhabdomeres.
","abstract_html":"<p>Rumi is a protein <em>O-</em>glucosyltransferase that adds the sugar <em>O-</em>glucose onto the serine in the target sequence C-S-X-S-(P/A)-C found within properly folded EGF repeats. It was first discovered to modify the <em>Drosophila </em>Notch extracellular domain and to be required for Notch signaling in a temperature dependent manner, but other targets of Rumi remained unknown. Several other proteins in the <em>Drosophila </em>proteome harbor multiple consensus sequence highly predictive of <em>O-</em>glucose, including the transmembrane protein Crumbs and the secreted protein Eyes shut (Eys). Both of these proteins are required for proper eye development and mutations in their human homologs cause a blindness disorder named retinitis pigmentosa. Therefore, we sought to determine whether Rumi plays a role in photoreceptor development. We found that <em>rumi<sup>–/–</sup></em> animals have defects in photoreceptor spacing in which many neighboring rhabdomeres are attached. This phenotype cannot be explained by the loss of <em>O-</em>glucose on Notch or Crumbs. However, <em>eys </em>genetically interacts with <em>rumi</em>, and in <em>rumi<sup>–/–</sup></em> animals at the start of rhabdomere separation, Eys accumulates intracellularly and decreased levels of Eys reach the extracellular space. Overexpressing a mutant Eys transgene which contains no intact <em>O-</em>glucosylation sites also results in intracellular accumulation of Eys, suggesting that loss of <em>O-</em>glucose from Eys is the cause. Additionally, both the intracellular accumulation and the rhabdomere attachment defect grow more severe at higher temperatures, and Eys degrades at higher temperatures in <em>rumi<sup>–/–</sup></em>. In addition, removing one copy of the chaperone <em>Hsc70-3 </em>enhances the <em>rumi<sup>–/–</sup></em> phenotype. Together, these data suggest that loss of <em>O-</em>glucose from Eys causes a defect in its proper folding, which leads to decreased Eys reaching the extracellular space and therefore a failure in full separation of the rhabdomeres.</p>","abstract_has_math":false,"creators":["Haltom, Amanda"],"institution":null,"degree_name":"Doctor of Philosophy (PhD)","degree_level":"Dissertation (PhD)","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Hamed Jafar-Nejad","William Mattox","Michael Galko"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-05-01T07:00:00Z","date_published":"2015-05-01T07:00:00Z","updated_at":"2026-07-24T05:49:41Z","subjects":["Rumi","glycosylation","O-glucosylation","photoreceptor","Eyes shut","Eys","Developmental Biology","Genetics","Medicine and Health Sciences"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://digitalcommons.library.tmc.edu/utgsbs_dissertations/551","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Hamed Jafar-Nejad","William Mattox","Michael Galko"]},{"key":"dc:creator","label":"Author","values":["Haltom, Amanda"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2015-03-18T07:00:00Z"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation (PhD)"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Rumi","glycosylation","O-glucosylation","photoreceptor","Eyes shut","Eys","Developmental Biology","Genetics","Medicine and Health Sciences"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://digitalcommons.library.tmc.edu/utgsbs_dissertations/551"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Rumi is a protein O-glucosyltransferase that adds the sugar O-glucose onto the serine in the target sequence C-S-X-S-(P/A)-C found within properly folded EGF repeats. It was first discovered to modify the Drosophila Notch extracellular domain and to be required for Notch signaling in a temperature dependent manner, but other targets of Rumi remained unknown. Several other proteins in the Drosophila proteome harbor multiple consensus sequence highly predictive of O-glucose, including the transmembrane protein Crumbs and the secreted protein Eyes shut (Eys). Both of these proteins are required for proper eye development and mutations in their human homologs cause a blindness disorder named retinitis pigmentosa. Therefore, we sought to determine whether Rumi plays a role in photoreceptor development. We found that rumi–/– animals have defects in photoreceptor spacing in which many neighboring rhabdomeres are attached. This phenotype cannot be explained by the loss of O-glucose on Notch or Crumbs. However, eys genetically interacts with rumi, and in rumi–/– animals at the start of rhabdomere separation, Eys accumulates intracellularly and decreased levels of Eys reach the extracellular space. Overexpressing a mutant Eys transgene which contains no intact O-glucosylation sites also results in intracellular accumulation of Eys, suggesting that loss of O-glucose from Eys is the cause. Additionally, both the intracellular accumulation and the rhabdomere attachment defect grow more severe at higher temperatures, and Eys degrades at higher temperatures in rumi–/–. In addition, removing one copy of the chaperone Hsc70-3 enhances the rumi–/– phenotype. Together, these data suggest that loss of O-glucose from Eys causes a defect in its proper folding, which leads to decreased Eys reaching the extracellular space and therefore a failure in full separation of the rhabdomeres.
"]},{"key":"dc:title","label":"Title","values":["Elucidating The Role of Rumi and O-Glucosylation In The Drosophila Eye"]}]}],"canonical_facts":{"dc:contributor":["Hamed Jafar-Nejad","William Mattox","Michael Galko"],"dc:creator":["Haltom, Amanda"],"dc:date.available":["2015-03-18T07:00:00Z"],"dc:description.abstract":["Rumi is a protein O-glucosyltransferase that adds the sugar O-glucose onto the serine in the target sequence C-S-X-S-(P/A)-C found within properly folded EGF repeats. It was first discovered to modify the Drosophila Notch extracellular domain and to be required for Notch signaling in a temperature dependent manner, but other targets of Rumi remained unknown. Several other proteins in the Drosophila proteome harbor multiple consensus sequence highly predictive of O-glucose, including the transmembrane protein Crumbs and the secreted protein Eyes shut (Eys). Both of these proteins are required for proper eye development and mutations in their human homologs cause a blindness disorder named retinitis pigmentosa. Therefore, we sought to determine whether Rumi plays a role in photoreceptor development. We found that rumi–/– animals have defects in photoreceptor spacing in which many neighboring rhabdomeres are attached. This phenotype cannot be explained by the loss of O-glucose on Notch or Crumbs. However, eys genetically interacts with rumi, and in rumi–/– animals at the start of rhabdomere separation, Eys accumulates intracellularly and decreased levels of Eys reach the extracellular space. Overexpressing a mutant Eys transgene which contains no intact O-glucosylation sites also results in intracellular accumulation of Eys, suggesting that loss of O-glucose from Eys is the cause. Additionally, both the intracellular accumulation and the rhabdomere attachment defect grow more severe at higher temperatures, and Eys degrades at higher temperatures in rumi–/–. In addition, removing one copy of the chaperone Hsc70-3 enhances the rumi–/– phenotype. Together, these data suggest that loss of O-glucose from Eys causes a defect in its proper folding, which leads to decreased Eys reaching the extracellular space and therefore a failure in full separation of the rhabdomeres.
"],"dc:identifier":["https://digitalcommons.library.tmc.edu/utgsbs_dissertations/551"],"dc:subject":["Rumi","glycosylation","O-glucosylation","photoreceptor","Eyes shut","Eys","Developmental Biology","Genetics","Medicine and Health Sciences"],"dc:title":["Elucidating The Role of Rumi and O-Glucosylation In The Drosophila Eye"],"thesis:degree_level":["Dissertation (PhD)"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T05:49:41Z"}