Meeting Abstract

128.3  Tuesday, Jan. 7 14:00  Stem cells in a colonial animal with localized growth zones SIEBERT, S*; GOETZ, FE; CHURCH, SH; BHATTACHARYYA, P; ZAPATA, F; HADDOCK, SHD; DUNN, CW; Brown University, Providence; Brown University, Providence; Brown University, Providence; Brown University, Providence; Brown University, Providence; Monterey Bay Aquarium Research Institute, Moss Landing; Brown University, Providence stefan_siebert@brown.edu

Siphonophores are planktonic marine Cnidarians with complex colonial organization. The different bodies, or zooids, of a colony show functional specialization and are arranged in a highly organized manner. Cellular dynamics of siphonophore growth are, however, not understood. We identified interstitial stem cells that express five canonical stem cell and germ line markers at distinct, well-defined locations in colonies of Nanomia bijuga. These locations are the tips of the two localized growth zones, young zooid buds, and particular locations within the maturing and the mature zooids. The expression of these stem cell genes is strongest early in zooid formation and development, and becomes more restricted as zooids mature until it disappears from most zooid regions. Germ cells are segregated early in one of the growth zones. Expression persists the longest in gametogenic and cnidogenic regions and in regions where cell proliferation and differentiation is known to continuously occur such as tentacle bases. No cells expressing these stem cell markers were identified in the stem to which zooids are attached, or at locations within zooids that would suggest that stem cells migrate within or between zooids. Maintenance of self-renewing multipotent cells in the growth zone and deposition of populations of stem cells in particular places within zooids allow for a highly organized and an almost meristem-like growth pattern in siphonophores.