Developmental potential of fused Caenorhabditis elegans oocytes: generation of giant and twin embryos

Abstract

With their first cleavage blastomeres in Caenorhabditis elegans are fixed to very different developmental programs going along with differential segregation of maternal gene products. To investigate whether indications for a prelocalization of cytoplasmic components can already be found in unfertilized egg cells, we fused mature C. elegans oocytes with the help of a laser microbeam. Fertilization of two fused oocytes resulting in triploid zygotes showed an essentially normal early cleavage pattern with the establishment of five somatic cell lineages and a germline and also a normal spatial arrangement of blastomeres. A considerable fraction of such embryos hatched and developed into fertile giant nematodes. The numbers of cell nuclei in freshly hatched and adult giant animals were found to be essentially the same as in untreated controls. When three fused oocytes were fertilized, two alternative patterns of early embryogenesis were observed. Half of the embryos followed the normal cleavage mode. The other half, however, developed in a twin-like fashion with all cells present in two copies, apparently due to fertilization by two sperm. In such embryos, two areas of gastrulation were established, resulting in the generation of two separate gut primordia. In summary, our results suggest that (1) in contrast to the uncleaved zygote in the mature oocyte of C. elegans no cytoplasmic regionalization exists, (2) the invariable cell numbers typical for the C. elegans embryo are not controlled via cell size, and (3) the entry of a second sperm can induce a cascade of events in the egg leading to the formation of two complete embryo anlagen.

Egg development in parthenogenetic nematodes: variations in meiosis and axis formation

“…Living adults were mounted on microscope slides carrying thin 5% agar pads as described in Irle and Schierenberg, 2002. Preparations of living embryos on 3% agar-coated slides were performed according to Lahl et al (2003).…”

Caenorhabditis elegans neuronal regeneration is influenced by life stage, ephrin signaling, and synaptic branching

“…Such ectopic expression may be due to laser-induced membrane fusion and GFP mixing between the axotomized cells and adjacent processes. Membrane fusion induced by UV laser irradiation has been observed in C. elegans embryos and oocytes (51,52). We scored regrowth of a cut axon in such cases only when it could be unambiguously distinguished from ectopic GFP expression in a neighboring process.…”

Versatile optical manipulation system for inspection, laser processing, and isolation of individual living cells

“…Furthermore, multiple traps allow stretching of objects to measure structural changes under tension 22,64 or interactions between objects, e.g., adhesion properties between cells ͑such as between an antigen-presenting cell and a lymphocyte͒ or artificial constructs such as ligand coated beads. Alternatively, the ultraviolet laser could be used to induce fusion of multiple individual cells 42,43 brought in contact with optical traps.…”

“…39 Transient permeabilization of the cell plasma membrane by short-term laser irradiation allows localized injection of genes or biomolecules ͑optoinjection͒ 40,41 as well as fusion of individual cells. 42,43 Laser pressure catapulting can be used to isolate and collect specific cellular components for subsequent molecular processing 39,44 or living cells for recultivation, 45 allowing efficient sample recovery without contamination from unselected material.…”