Cell lineage, cell-cell interaction, and segment formation in the ectoderm of a glossiphoniid leech embryo

Zackson, Saul L.

doi:10.1016/0012-1606(84)90044-7

Cited by 112 publications

(100 citation statements)

References 14 publications

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“…N teloblasts in stage 7 embryos (~33 hours AZD) were injected with RDA and nGFP mRNA, After ~48 hours of subsequent development, the pattern of nGFP-labeled nuclei was as expected from previous studies (Zackson, 1984;Bissen and Weisblat, 1989) (not shown). In other experiments, we allowed injected embryos to develop for 143 hours postinjection.…”

Section: Resultssupporting

confidence: 76%

“…These results indicate that the asymmetric divisions of nf and ns cell are under tight, differential control. Asymmetric cell divisions are a prominent feature of the stereotyped division patterns throughout the segmental and non-segmental tissues of the Helobdella embryo (Zackson, 1984;Shankland, 1987;Huang et al, 2002); we find that later divisions within the ns and nf blast cell lineages are also asymmetric. Whether such asymmetries are essential for establishing fate differences or merely a reflection of those differences remains to be determined.…”

Section: Application Of the Mrna Injection Technique To Analysis Of Tsupporting

confidence: 56%

“…Injected mRNA is degraded more quickly in the blast cells than in the teloblast, and more quickly within the germinal bands than in the bandlets. Previous work has shown that blast cells accumulate transcripts more rapidly than teloblasts (Bissen and Weisblat, 1991) and there is a dramatic prolongation of the cell cycle in blast cells relative to teloblasts (Zackson, 1984;Bissen and Weisblat, 1989). These features support the idea that the teloblast-to-blast cell transition in leech is analogous to the 'mid-blastula transition' in Xenopus and Drosophila (reviewed by Yasuda and Schubiger, 1992).…”

Section: Discussion Mrna Injections In Helobdellamentioning

confidence: 96%

“…In contrast to known vertebrate and arthropod systems, segmentation in Helobdella proceeds via stereotyped lineages, beginning with the first mitosis and continuing, so far as is known, through the formation of terminally differentiated, segmentally iterated cells (Whitman, 1878;Zackson, 1984;Kramer and Weisblat, 1985;Weisblat and Shankland, 1985;Bissen and Weisblat, 1989;Braun and Stent, 1989;Shankland 1987;Muller et al, 1981). This assertion is qualified by the fact that no complete lineages for any definitive segmental progeny have been published.…”

Section: Introductionmentioning

confidence: 99%

“…Each teloblast lineage exhibits a specific pattern of blast cell division patterns (Zackson, 1984;Bissen and Weisblat, 1989). For the N and Q lineages, this includes differences in the timing and symmetry of the early divisions of alternating blast cells, designated as nf and ns, qf and qs, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Applications of mRNA injections for analyzing cell lineage and asymmetric cell divisions during segmentation in the leechHelobdella robusta

Zhang

Weisblat

2005

Development

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Synthetic mRNAs can be injected to achieve transient gene expression even for `non-model' organisms in which genetic approaches are not feasible. Here,we have used this technique to express proteins that can serve as lineage tracers or reporters of cellular events in embryos of the glossiphoniid leech Helobdella robusta (phylum Annelida). As representatives of the proposed super-phylum Lophotrochozoa, glossiphoniid leeches are of interest for developmental and evolutionary comparisons. Their embryos are suitable for microinjection, but no genetic approaches are currently available. We have injected segmentation stem cells (teloblasts) with mRNAs encoding nuclear localized green fluorescent protein (nGFP) and its spectral variants, and have used tandem injections of nGFP mRNA followed by antisense morpholino oligomer (AS MO), to label single blast cell clones. These techniques permit high resolution cell lineage tracing in living embryos. We have applied them to the primary neurogenic (N) lineage, in which alternate segmental founder cells (nf and ns blast cells) contribute distinct sets of progeny to the segmental ganglia. The nf and ns blast cell clones exhibit strikingly different cell division patterns: the increase in cell number within the nf clone is roughly linear, while that in the ns clone is almost exponential. To analyze spindle dynamics in the asymmetric divisions of individual blast cells, we have injected teloblasts with mRNA encoding a tau::GFP fusion protein. Our results show that the asymmetric divisions of n blast cells result from a posterior shift of both the spindle within the cell and the midbody within the mitotic spindle, with differential regulation of these processes between nf and ns.

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Section: Resultssupporting

confidence: 76%

Section: Application Of the Mrna Injection Technique To Analysis Of Tsupporting

confidence: 56%