title: Localization of polyadenylated RNAs during teloplasm formation and cleavage in leech embryos.
abstract: In the embryos of glossiphoniid leeches, as in many annelids, cytoplasmic reorganization prior to first cleavage generates domains of yolk-deficient cytoplasm (called teloplasm) that are sequestered during the first three cell divisions to the D' macromere. Subsequently, the D' macromere generates a set of embryonic stem cells (teloblasts) that are the progenitors of the definitive segmental tissues. The hypothesis that fate-determining substances are localized within the teloplasm and segregated to the D' macromere during cleavage is supported by experiments in which a redistribution of yolk-defcient cytoplasm changes the fate of blastomeres that inherit it (Astrow et al. 1987; Devries 1973; Nelson and Weisblat 1992). As a step toward identifying fate-determining factors in teloplasm, we describe the distribution of polyadenylated RNAs (polyA+ RNA) in the early embryo of the leech, Helobdella triserialis, as inferred from in situ hybridization using tritiated polyuridylic acid (3H-polyU). Our results indicate that polyA+ RNA colocalizes with teloplasm during cytoplasmic rearrangements resulting in teloplasm formation, and that it remains concentrated in the teloplasm during the cell divisions and a second cytoplasmic rearrangement during early embryogenesis. Lesser amounts of polyA+ RNA appear to be localized in cortical cytoplasm at most stages.
authors.affiliation: Department of Biology and Microbiology, University of Wisconsin, 54901, Oshkosh, WI, USA.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Holton
authors.affiliation: Department of Cell Biology and Anatomy, New York Medical College, 10595, Valhalla, NY, USA.
authors.forename: Cathy J
authors.initials: CJ
authors.lastname: Wedeen
authors.affiliation: Department of Biological Sciences, University of Southern California, 90089, Los Angeles, CA, USA.
authors.forename: Stephanie H
authors.initials: SH
authors.lastname: Astrow
authors.affiliation: Department of Molecular and Cell Biology, University of California, 385 LSA, 94720, Berkeley, CA, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Weisblat
keywords: Annelid; Leech; Maternal RNA