title: Exploration of embryonic origins of germline stem cells and neoblasts in Enchytraeus japonensis (Oligochaeta, Annelida).
abstract: An oligochaete annelid species, Enchytraeus japonensis, reproduces not only asexually but also sexually. It has been reported that putative mesodermal stem cells called neoblasts contribute to blastema formation and that Ej-piwi(+) germline stem cells participate in gonadal regeneration. To delineate the origin and formation of both of these stem cells, we isolated two vasa-related genes (Ej-vlg1 and Ej-vlg2) and analyzed the expression of each along with that of germline marker gene Ej-piwi. In adults, Ej-vlg1 and Ej-vlg2 were expressed in Ej-piwi(+) germline stem cells and germ cells in gonads, while only Ej-vlg2 mRNAs were detected in neoblasts. Expression analysis during embryogenesis indicated that clusters of Ej-vlg1(+)/Ej-vlg2(+) cells, located at the posterior ventral region in late embryos, became Ej-vlg1(+)/Ej-vlg2(+)/Ej-piwi(+) germline stem cells just after embryogenesis. On the other hand, Ej-vlg2 single positive cells with morphological characteristics of neoblasts became detectable much later after embryogenesis at the ventral position on each septum where adult neoblasts exist, although these early detected cells were much smaller in size than adult neoblasts. The present results suggest that (1) germline stem cells specified just after embryogenesis are derived from Ej-vlg1(+)/Ej-vlg2(+) cells which appear at the posterior ventral region in late embryos, and that (2) neoblasts appear much later in development.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, N10, W8, Kita-ku, Sapporo 060-0810, Japan. mutumi@bio.sci.hokudai.ac.jp
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Sugio
authors.forename: Kazunari
authors.initials: K
authors.lastname: Takeuchi
authors.forename: Junko
authors.initials: J
authors.lastname: Kutsuna
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Tadokoro
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Chikako
authors.initials: C
authors.lastname: Yoshida-Noro
authors.forename: Shin
authors.initials: S
authors.lastname: Tochinai
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D015415:Biomarkers / Q000737:chemistry / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D047108:Embryonic Development; D005854:Germ Cells / Q000166:cytology* / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology; D008969:Molecular Sequence Data; D009835:Oligochaeta / Q000166:cytology* / Q000196:embryology* / Q000378:metabolism; D016415:Sequence Alignment; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism
chemical_list: D015415:Biomarkers