title: Characterization of Notch-class gene expression in segmentation stem cells and segment founder cells in Helobdella robusta (Lophotrochozoa; Annelida; Clitellata; Hirudinida; Glossiphoniidae).
abstract: To understand the evolution of segmentation, we must compare segmentation in all three major groups of eusegmented animals: vertebrates, arthropods, and annelids. The leech Helobdella robusta is an experimentally tractable annelid representative, which makes segments in anteroposterior progression from a posterior growth zone consisting of 10 identified stem cells. In vertebrates and some arthropods, Notch signaling is required for normal segmentation and functions via regulation of hes-class genes. We have previously characterized the expression of an hes-class gene (Hro-hes) during segmentation in Helobdella, and here, we characterize the expression of an H. robusta notch homolog (Hro-notch) during this process. We find that Hro-notch is transcribed in the segmental founder cells (blast cells) and their stem-cell precursors (teloblasts), as well as in other nonsegmental tissues. The mesodermal and ectodermal lineages show clear differences in the levels of Hro-notch expression. Finally, Hro-notch is shown to be inherited by newly born segmental founder cells as well as transcribed by them before their first cell division.
authors.affiliation: Department of Molecular and Cell Biology, 385 LSA University of California, Berkeley, CA 94720-3200, USA.
authors.forename: Ajna S
authors.initials: AS
authors.lastname: Rivera
authors.forename: Foster C
authors.initials: FC
authors.lastname: Gonsalves
authors.forename: Mi Hye
authors.initials: MH
authors.lastname: Song
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Norris
authors.forename: David A
authors.initials: DA
authors.lastname: Weisblat
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D019070:Cell Lineage / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D007865:Leeches / Q000166:cytology / Q000196:embryology* / Q000235:genetics; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*
chemical_list: D051880:Receptors, Notch