title: Conservative segregation of maternally inherited CS histone variants in larval stages of sea urchin development.
abstract: Three sets of histone variants are coexisting in the embryo at larval stages of sea urchin's development: the maternally inherited cleavage stage variants (CS) expressed during the two initial cleavage divisions, the early histone variants, which are recruited into embryonic chromatin from middle cleavage stages until hatching and the late variants, that are fundamentally expressed from blastula stage onward. Since the expression of the CS histones is confined to the initial cleavage stages, these variants represent a very minor proportion of the histones present in the plutei larvae, whereas the late histone variants are predominant. To determine the position of these CS in the embryonic territories, we have immunolocalized the CS histone variants in plutei larvas harvested 72 h post-fertilization. In parallel, we have pulse labeled the DNA replicated during the initial cleavage cycle with bromodeoxyuridine (BrdU) and its position was further determined in the plutei larvas by immunofluorescence. We have found that the CS histone variants were segregated to specific territories in the plutei. The position in which the CS histone variants were found to be segregated was consistent with the position in which the DNA molecules that were replicated during the initial cleavage divisions were localized. These results strongly suggest that a specification of embryonic nuclei occurs at the initial cleavage divisions which is determined by a chromatin organized by CS histone variants.
authors.affiliation: Departamento de Biología Molecular, Universidad de Concepción, Casilla 160-C Concepción, Chile.
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Oliver
authors.forename: Carla
authors.initials: C
authors.lastname: Rodríguez
authors.forename: Paula
authors.initials: P
authors.lastname: Bustos
authors.forename: Violeta
authors.initials: V
authors.lastname: Morín
authors.forename: Soraya
authors.initials: S
authors.lastname: Gutierrez
authors.forename: Martín
authors.initials: M
authors.lastname: Montecino
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Genevière
authors.forename: Marcia
authors.initials: M
authors.lastname: Puchi
authors.forename: María
authors.initials: M
authors.lastname: Imschenetzky
mesh_terms: D000818:Animals; D036703:Blastula / Q000378:metabolism; D015153:Blotting, Western; D001973:Bromodeoxyuridine; D004247:DNA / Q000032:analysis / Q000096:biosynthesis; D005306:Fertilization; D014644:Genetic Variation; D006657:Histones / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D007814:Larva / Q000254:growth & development / Q000502:physiology; D008856:Microscopy, Fluorescence; D012617:Sea Urchins / Q000502:physiology*; D013997:Time Factors
chemical_list: D006657:Histones; D004247:DNA; D001973:Bromodeoxyuridine