Scanning electron microscopy of amphibian lampbrush chromosomes

Angelier, Nicole; Paintrand, M; Lavaud, Anne; Lechaire, Jean‐Pierre

doi:10.1007/bf00292471

Cited by 25 publications

(12 citation statements)

References 19 publications

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“…These particles can aggregate to a greater or lesser extent such that in some loops they form higher order particles or globules large enough to be resolved by the light microscope and imparting a characteristic morphology to the matrices of those loops (reviewed in Callan 1986). Moreover, in the scanning electron microscope studies of Angelier et al 1984 it is clear that the RNP particles or "bodies" of various dimensions are arranged helically around loop axes and that in cases where larger bodies form by aggregation their close packing causes the formation of a "continuous spiral sleeve encircling the loop axis". The latter description also accurately portrays the effect of RBM6 on loop morphology that we observed with the light microscope and we conclude that this unique morphological effect ultimately reflects the spiral arrangement of nascent RNP around highly active transcription units that is not normally apparent.…”

Section: Rbm6 Multimerization and The Formation Of Novel Nuclear Strumentioning

confidence: 99%

Subnuclear targeting of the RNA-binding motif protein RBM6 to splicing speckles and nascent transcripts

2010

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RNA-binding motif (RBM) proteins comprise a large family of RNA-binding proteins whose functions are poorly understood. Since some RBM proteins are candidate alternative splicing factors we examined whether one such member of the family, RBM6, exhibited a pattern of nuclear distribution and targeting consistent with this role. Using antibodies raised against mouse RBM6 to immunostain mammalian cell lines we found that the endogenous protein was both distributed diffusely in the nucleus and concentrated in a small number of nuclear foci that corresponded to splicing speckles/interchromatin granule clusters (IGCs). Tagged RBM6 was also targeted to IGCs, although it accumulated in large bodies confined to the IGC periphery. The basis of this distribution pattern was suggested by the targeting of tagged RBM6 in the giant nuclei (or germinal vesicles (GVs)) of Xenopus oocytes. In spread preparations of GV contents RBM6 was localized both to lampbrush chromosomes and to the surface of many oocyte IGCs, where it was confined to up to 50 discrete patches. Each patch of RBM6 labelling corresponded to a bead-like structure of 0.5-1 microm diameter that assembled de novo on the IGC surface. Assembly of these novel structures depended on the repetitive N-terminal region of RBM6, which acts as a multimerization domain. Without this domain, RBM6 was no longer excluded from the IGC interior but accumulated homogeneously within it. Assembly of IGC-surface structures in mammalian cell lines also depended on the oligomerization domain of RBM6. Oligomerization of RBM6 also had morphological effects on its other major target in GVs, namely the arrays of nascent transcripts visible in lampbrush chromosome transcription units. The presence of oligomerized RBM6 on many lampbrush loops caused them to appear as dense structures with a spiral morphology that appeared quite unlike normal, extended loops. This distribution pattern suggests a new role for RBM6 in the co-transcriptional packaging or processing of most nascent transcripts.

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Section: Rbm6 Multimerization and The Formation Of Novel Nuclear Strumentioning

confidence: 99%

Subnuclear targeting of the RNA-binding motif protein RBM6 to splicing speckles and nascent transcripts

2010

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“…In amphibia, particulate aggregates were shown to be parts of the loop matrix of lampbrush chromosomes by examining sections of both nuclei fixed entire and end-embedded spread preparations [16,21,22]. Likewise, using scanning electron microscopy, the loop matrix was seen to be constituted of 100-200 nm bodies [23]. In mammals, electron opaque granules were observed close Downloaded by [JAMES COOK UNIVERSITY] at 10:31 17 March 2015 294 to diplotene chromosomes in the antral follicle of the prepubertal mouse [24], as well as 'clusters of granules' in association with chromosomal 'lateral projections' and loops in primordial oocytes of primates [18,25].…”

Section: Transcription Productsmentioning

confidence: 99%

Ultrastructural cytochemistry of the chromosomes of growing oocytes ofPerinereis cultrifera(Nereidae, Polychaeta, Annelida) after fixation in situ

Bertout

1986

International Journal of Invertebrate Reproduction and Developm

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In situ cytochemical study of oocytes of Perinereis demonstrated that the so-called 'nucleoplasmic granulations' (NG) are in fact sections of diplotene chromosomes active in transcription. Indeed, with the osmium-ammine Feulgen-like reaction, a first type of NG, the fibrillar clumps, were shown to contain nucleosomal DNA. Therefore, fibrillar clumps represent chromatin of bivalents. These chromatin clumps frequently exhibit a ring-like configuration due to the presence at their center of a non DNA-containing core. The latter could correspond, in section, to the proteinaceous chromosomal axis as suggested after in situ silver staining. The second type of NG, the dense aggregates, were stained with the EDTA regressive procedure preferential for RNP, indicating that they are transcription products. Evidence is presented that these RNP are of chromosomal origin. Similarities between the nuclear RNP-rich aggregates of oocytes of Perinereis and the loop matrix of lampbrush chromosomes are considered.

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“…It is both extensible and contractible. The contractibility of the loop results in the contraction and dilation of the chromomere (Angelier et al, 1984(Angelier et al, , 1990(Angelier et al, , 1996Chelysheva et al, 1990;Macgregor, 1987;Morgan, 2002).…”

Section: Lampbrush Chromosomesmentioning

confidence: 99%