title: Flatworm stem cells and the germ line: developmental and evolutionary implications of macvasa expression in Macrostomum lignano.
abstract: We have isolated and identified the vasa homologue macvasa, expressed in testes, ovaries, eggs and somatic stem cells of the flatworm Macrostomum lignano. Molecular tools such as in situ hybridization and RNA interference were developed for M. lignano to study gene expression and function. Macvasa expression was followed during postembryonic development, regeneration and in starvation experiments. We were able to follow gonad formation in juveniles and the reformation of gonads from stem cells after amputation by in situ hybridization and a specific Macvasa antibody. Expression of macvasa in the germ cells was highly affected by feeding conditions and correlated with the decrease and regrowth of the gonads. RNA interference showed specific down-regulation of macvasa mRNA and protein. The absence of Macvasa did not influence gonad formation and stem cell proliferation. Our results corroborate the exclusive nature of the flatworm stem cell system but challenge the concept of a solely postembryonic specification of the germ line in Platyhelminthes. We address the transition of somatic stem cells to germ cells and speculate on Macrostomum as a system to unravel the mechanisms of preformation or epigenesis in the evolution of germ line specification from somatic stem cells.
authors.affiliation: University of Innsbruck, Institute of Zoology, Technikerstrasse 25, A-6020 Innsbruck, Austria. Daniela.Pfister@uibk.ac.at
authors.forename: Daniela
authors.initials: D
authors.lastname: Pfister
authors.forename: Katrien
authors.initials: K
authors.lastname: De Mulder
authors.forename: Volker
authors.initials: V
authors.lastname: Hartenstein
authors.forename: Georg
authors.initials: G
authors.lastname: Kuales
authors.forename: Gaetan
authors.initials: G
authors.lastname: Borgonie
authors.forename: Florentine
authors.initials: F
authors.lastname: Marx
authors.forename: Joshua
authors.initials: J
authors.lastname: Morris
authors.forename: Peter
authors.initials: P
authors.lastname: Ladurner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D053487:DEAD-box RNA Helicases / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D005854:Germ Cells / Q000166:cytology / Q000378:metabolism*; D015801:Helminth Proteins / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D013234:Stem Cells / Q000378:metabolism*; D014419:Turbellaria / Q000166:cytology* / Q000254:growth & development* / Q000502:physiology
chemical_list: D015801:Helminth Proteins; D053487:DEAD-box RNA Helicases