title: Distinct chromatin organization in the germ line founder cell of the Caenorhabditis elegans embryo.
abstract: Cells belonging to the germ lineage segregate physically and molecularly from their somatic neighbors during embryogenesis. While germ line-specific chromatin modifications have been identified at later stages in the Caenorhabditis elegans nematode, none have been found in the single P4 germ line founder cell that arises at the beginning of gastrulation. Using light and electron microscopy, we now report that the chromatin organization in the germ line founder cell of the early C. elegans embryo is distinct from that in the neighboring somatic cells. This unique organization is characterized by a greater chromatin compaction and an expansion of the interchromatin compartment. The ultrastructure of individual chromatin domains does not differ between germ line and somatic cells, pointing to a specific organization mainly at the level of the whole nucleus. We show that this higher order reorganization of chromatin is not a consequence of the P4 nucleus being smaller than somatic nuclei or having initiated mitosis. Imaging of living embryos expressing fluorescent markers for both chromatin and P granules revealed that the appearance of a distinct chromatin organization in the P4 cell occurs approximately 10 min after its birth and coincides with the aggregation of P granules around the nucleus, suggesting a possible link between these two events. The higher order reorganization of chromatin that is reported here occurs during the establishment of definitive germ cell identity. The changes we have observed could therefore be a prerequisite for the programming of chromatin totipotency.
authors.affiliation: Institute of Cellular Biology and Pathology, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
authors.forename: Lenka
authors.initials: L
authors.lastname: Vágnerová
authors.forename: Adriána
authors.initials: A
authors.lastname: Gombitová
authors.forename: Dušan
authors.initials: D
authors.lastname: Cmarko
authors.forename: Christian
authors.initials: C
authors.lastname: Lanctôt
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000648:ultrastructure; D002843:Chromatin / Q000378:metabolism* / Q000648:ultrastructure; D042002:Chromatin Assembly and Disassembly / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D002843:Chromatin
keywords: Caenorhabditis elegans; chromatin; germ line; interchromatin compartment; live cell microscopy