Chromatin organization in nuclei of sea urchin embryos. Comparison with the chromatin organization of the sperm

Spadafora, Corrado; Noviello, Luigi; Geraci, G.

doi:10.1016/0045-6039(76)90033-6

Cited by 14 publications

(1 citation statement)

References 19 publications

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“…This differential susceptibility to nuclease seems to be a common trend among chromatins from related developing systems. Thus, sea urchin embryo chromatin appears to be rather resistant to enzyme fragmentation (Spadafora et al, 1976b), although the readily accessible regions are easily degraded to soluble nucleotides. Almost all embryo chromatin is rendered acid soluble on prolonged digestion.…”

Section: Discussionmentioning

confidence: 99%

Nucleosome organization during germ cell development in the sea cucumber Holothuria tubulosa

Cornudella¹,

Rocha²

1979

Biochemistry

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Conformational changes that occur in chromatin from developing germ cells of the echinoderm Holothuria tubulosa have been probed with micrococcal nuclease. The results indicate that the extent of DNA degradation to acid-soluble nucleotides is highest in chromatin at the early stages of gonad growth, being drastically subdued in the mature sperm cell. Production of nucleosomal particles also varies with development, involving at least 70% of the chromatin at the final stage of maturation, whereas in immature germ cells it remains much lower. In contrast, electrophoretic analysis for DNA size has shown that the average nucleosome repeat length, about 227 base pairs, does not change throughout the maturation process. However, kinetics of the enzyme reaction have revealed that, although brief digestion of chromatin from both immature gonads and sperm yields comparable series of higher oligomers, extensive digest patterns differ widely. Sperm chromatin, highly protected, releases a 275 base pair intermediate fragment, wholly absent in immature gonads. The 145 base pair core released in both chromatins is not further digested in sperm. In comparison to sperm chromatin, that of immature germ cells is much more susceptible to fragmentation, yielding the usual set of smaller subnucleosomal fragments. These data suggest the induction of differential accessibilities of chromatin DNA with maturation, which is not accompanied by displacement of the histone complement. The histone variants present in this species may well be instrumental in the process.

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Section: Discussionmentioning

confidence: 99%

Nucleosome organization during germ cell development in the sea cucumber Holothuria tubulosa

Cornudella¹,

Rocha²

1979

Biochemistry

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Ultrastructural organization of heterochromatin within sea urchin sperm nuclei

Aboukarsh

Kunkle

1985

Gamete Research

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Chromatin within swollen or lysed isolated sperm nuclei of the sea urchin, Strongylocentrotus purpuratus, was examined by electron microscopy. Spread preparations of lysed sperm nuclei demonstrated dense aggregates of nondispersed material and beaded filaments radiating from these aggregates. These beaded fibers are similar in size and appearance to the “beads‐on‐a‐string” seen as characteristic of chromatin spreads from numerous interphase nuclei. The beads are nucleosomes that have an average diameter of 130 Å. The interconnecting string is 40 Å indiameter and corresponds to the spacer DNA. In thin sections of swollen nuclei the sperm chromatin appears to be composed of 400 Å superbeads that are closely apposed to form 400 Å fibers. As the chromatin disperses, the superbeads are seen to be attached to one another by chromatin fibers of 110 Å diameter. In thin sections, the 400 Å superbeads appear to disperse directly into the 110 Å fibers with no intervening structures. This work demonstrates that the heterochromatin in Strongylocentrotus purpuratus sperm nuclei is composed of nucleosomes that form 100 Å filaments that are compacted into 400 Å superbeads. The superbeads coalesce to give the morphological appearance of 400 Å fibers.

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Structural organization of the sperm chromatin in a fern (Scolopendrium vulgare) studied by spreading methods

Khlifi

1987

Gamete Research

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To investigate chromatin organization, we applied the spreading techniques to nuclei isolated from Scolopendrium spermatozoids. Well-dispersed chromatin shows three types of fibers: beaded fibers corresponding to a nucleosomal filament with adjacent nucleosomes in close contact, smooth fibers (14 nm in diameter) associated in a complex network, and knobby fibers constituted by local supercoiling of a very thin (4 nm) smooth filament. Along the knobby fibers, beads of variable size are irregularly spaced. The knobby fibers lie parallel and coalesce in thick bundles. The sperms basic proteins identified by electrophoretic analysis probably promote the supercoiling and the side-to-side attachment of the knobby fibers, which are all the more abundant in spread preparations. These results indicate that knobby fibers are probably located in the outer part of the sperm nucleus in which the chromatin is densely packed. As for the nucleosomal and smooth filaments, they may be situated in the inner part.

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Chromatin organization in nuclei of sea urchin embryos. Comparison with the chromatin organization of the sperm

Cited by 14 publications

References 19 publications

Nucleosome organization during germ cell development in the sea cucumber Holothuria tubulosa

Nucleosome organization during germ cell development in the sea cucumber Holothuria tubulosa

Ultrastructural organization of heterochromatin within sea urchin sperm nuclei

Structural organization of the sperm chromatin in a fern (Scolopendrium vulgare) studied by spreading methods

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