Lineage and fate of each blastomere of the eight-cell sea urchin embryo.

Abstract

A fluoresceinated lineage tracer was injected into individual blastomeres of eight-cell sea urchin(Strongylocentrotus purpuratus) embryos, and the location of the progeny of each blastomere was determined in the fully developed pluteus. Each blastomere gives rise to a unique portion of the advanced embryo. We confirm many of the classical assignments of cell fate along the animal-vegetal axis of the cleavage-stage embryo, and demonstrate that one blastomere of the animal quartet at the eight-cell stage lies nearest the future oral pole and the opposite one nearest the future aboral pole of the embryo. Clones of cells deriving from ectodermal founder cells always remain contiguous, while clones of cells descendant from the vegetal plate {i.e., gut, secondary mesenchyme) do not. The locations of ectodermal clones contributed by specific blastomeres require that the larval plane of bilateral symmetry lie approximately equidistant {i.e., at a 45 ° angle) from each of the first two cleavage planes. These results underscore the conclusion that many of the early spatial pattems of differential gene expression observed at the molecular level are specified in a clonal manner early in embryonic sea urchin development, and are each confined to cell lineages established during cleavage.

Rapid Evolution of Gastrulation Mechanisms in a Sea Urchin With Lecithotrophic Larvae

“…These results suggest that microinjection provides a nonintrusive means of marking cell clones in echinoderm embryos. Previous studies have reached the same conclusion (Cameron et al, 1987;Wray andRaff, 1989, 1990;Maruyama and Shinoda, 1990).…”

“…erythrogramma (Wray andRaff, 1989, 1990;Henry and Raff, 1990) than during planktotrophic development (Horstadius, 1973;Cameron et al, 1987). Asymmetrical cell movements during gastrulation place presumptive regions for the origin of mesenchyme cell populations at the tip of the archenteron at the appropriate time for ingression (Fig.…”

Role of the nanos homolog during sea urchin development

“…It has been reported that small micromere descendants contribute only to the adult rudiment (Cameron et al, 1987(Cameron et al, , 1991 and do not play any inductive roles in the signaling interaction that mediates blastomere specification (Khaner and Wilt, 1991). In contrast, it has been demonstrated that small micromere descendants have the potential for inducing presumptive ectoderm to form endomesoderm (Kurihara and Amemiya, 2005).…”

The dynamic gene expression patterns of transcription factors constituting the sea urchin aboral ectoderm gene regulatory network

“…At the pluteus stage, Na progenies become the abanal AE, which covers the midregion of the AE opposite of the anus opening. The great granddaughter cells of VA, left and right VL, contribute to the AE at the apex and the left and right anal plate AE, respectively, at the pluteus stage (Cameron et al, 1987(Cameron et al, , 1990(Cameron et al, , 1991. In addition, the granddaughter cells of the left and right NL develop into the left and right lateral AE (Cameron et al, 1990).…”

“…Using fluorescent lineage tracer injected into individual blastomeres of eight-cell sea urchin embryos, Cameron et al showed that the animal blastomere quartet (Na), the vegetal blastomere quartet (VA), and the four lateral blastomeres (left and right NL and VL) all contribute to the AE (Cameron et al, 1987). At the pluteus stage, Na progenies become the abanal AE, which covers the midregion of the AE opposite of the anus opening.…”