Universal nuclear domains of somatic and germ cells: some lessons from oocyte interchromatin granule cluster and Cajal body structure and molecular composition

Abstract

It is now clear that two prominent nuclear domains, interchromatin granule clusters (IGCs) and Cajal bodies (CBs), contribute to the highly ordered organization of the extrachromosomal space of the cell nucleus. These functional domains represent structurally stable but highly dynamic nuclear organelles enriched in factors that are required for different nuclear activities, especially RNA biogenesis. IGCs are considered to be the main sites for storage, assembly, and/or recycling of the essential spliceosome components. CBs are involved in the biogenesis of several classes of small RNPs as well as the modification of newly assembled small nuclear RNA. We have summarized data on the molecular composition, structure, and functional roles of IGCs and CBs in the nuclei of mammalian somatic cells and oocytes of some animals with a special focus on insects. We have focused on similarities and differences between the IGCs and CBs of oocytes and the well-studied CBs and IGCs of cultured mammalian somatic cells. We have shown the heterogeneous character of oocyte IGCs and CBs, both in structure and molecular content. We have also demonstrated the unique capacity of oocytes to form close structural interactions between IGC and CB components. We proposed to consider these joint structures as integrated entities, sharing the features of both IGCs and CBs.

Non-canonical Cajal bodies form in the nucleus of late stage avian oocytes lacking functional nucleolus

“…In contrast, this study describes extrachromosomal nuclear bodies (SGs and HSs), identiWed only in pigeon GVs, in which coilin is a speciWc component. In somatic cells of plants and animals, including chicken, coilin was shown to concentrate in distinct nuclear bodies, which correspond to CBs (Ochs et al 1995;Tucker et al 2001;Bogolyubov et al 2009). Using…”

“…It is well established that there are certain common RNAcontaining bodies in the oocyte nucleus, such as the nucleolus and interchromatin granule clusters (IGCs) (Mintz et al 1999;Morgan 2002;Gall et al 2004;Bogolyubov and Parfenov 2008;Bogolyubov et al 2009). Nevertheless, growing oocytes of adult birds of the studied orders were shown to lack functional nucleoli (reviewed in Gaginskaya et al 2009).…”

Perichromatin Fibrils Accumulation in Hepatocyte Nuclei Reveals Alterations of Pre-mRNA Processing During Aging

“…These roundish RNP structures, preferentially occurring in the perichromatin region (Monneron and Bernhard, 1969), would act as both vectors and storage site of already-spliced pre-mRNA (Fakan, 1994(Fakan, , 2004, and modifications in their number and=or molecular composition can reveal intranuclear pathway alterations (e.g., Puvion et al, 1977;Puvion-Dutilleul and Puvion, 1981;Lafarga et al, 1993;Zancanaro et al, 1993). On the other hand, interchromatin granules (IG), occurring as clusters in the interchromatin space, represent storage, assembly, and phosphorylation sites for transcription, and splicing factors (Puvion and Puvion-Dutilleul, 1996;Bogolyubov et al, 2009).…”

RNA processing is altered in skeletal muscle nuclei of patients affected by myotonic dystrophy

“…The structural counterpart of such macromolecular complexes is represented by the perichromatin fibrils (PF), fine fibrillar structures mainly distributed along the borders of the condensed chromatin (the so-called perichromatin region) which represent the form in situ of pre-mRNA transcription, splicing and 3 0 -end processing (reviews in Fakan 2004;. Other RNP-containing structures involved in pre-mRNA pathways are the perichromatin granules (PG) and the interchromatin granules (IG); PG are roundish structures which act as both vectors and storage sites of already spliced pre-mRNA (Fakan 2004), while IG occur as clusters in the interchromatin space, and represent the storage, assembly and phosphorylation sites for transcription and splicing factors (Puvion and Puvion-Dutilleul 1996;Bogolyubov et al 2009). …”