title: Identification of HECT E3 ubiquitin ligase family genes involved in stem cell regulation and regeneration in planarians.
abstract: E3 ubiquitin ligases constitute a large family of enzymes that modify specific proteins by covalently attaching ubiquitin polypeptides. This post-translational modification can serve to regulate protein function or longevity. In spite of their importance in cell physiology, the biological roles of most ubiquitin ligases remain poorly understood. Here, we analyzed the function of the HECT domain family of E3 ubiquitin ligases in stem cell biology and tissue regeneration in planarians. Using bioinformatic searches, we identified 17 HECT E3 genes that are expressed in the Schmidtea mediterranea genome. Whole-mount in situ hybridization experiments showed that HECT genes were expressed in diverse tissues and most were expressed in the stem cell population (neoblasts) or in their progeny. To investigate the function of all HECT E3 ligases, we inhibited their expression using RNA interference (RNAi) and determined that orthologs of huwe1, wwp1, and trip12 had roles in tissue regeneration. We show that huwe1 RNAi knockdown led to a significant expansion of the neoblast population and death by lysis. Further, our experiments showed that wwp1 was necessary for both neoblast and intestinal tissue homeostasis as well as uncovered an unexpected role of trip12 in posterior tissue specification. Taken together, our data provide insights into the roles of HECT E3 ligases in tissue regeneration and demonstrate that planarians will be a useful model to evaluate the functions of E3 ubiquitin ligases in stem cell regulation.
authors.affiliation: Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA.
authors.forename: Jordana M
authors.initials: JM
authors.lastname: Henderson
authors.affiliation: Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA.
authors.forename: Sean V
authors.initials: SV
authors.lastname: Nisperos
authors.affiliation: Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA.
authors.forename: Joi
authors.initials: J
authors.lastname: Weeks
authors.affiliation: Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA.
authors.forename: Mahjoobah
authors.initials: M
authors.lastname: Ghulam
authors.affiliation: Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas (IBV-CSIC), Valencia, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Marín
authors.affiliation: Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA. Electronic address: rzayas@mail.sdsu.edu.
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Zayas
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D010932:Planarians / Q000196:embryology* / Q000201:enzymology* / Q000235:genetics; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D034741:RNA, Small Interfering; D012038:Regeneration / Q000235:genetics*; D013234:Stem Cells / Q000166:cytology*; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics*
chemical_list: D034741:RNA, Small Interfering; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases
keywords: HECT; HUWE1; Planarian; Stem cells; TRIP12; WWP1