The Cajal body (CB) is a nuclear organelle present in all eukaryotes that have been carefully studied. It is identified by the signature protein coilin and by CB-specific RNAs (scaRNAs). CBs contain high concentrations of splicing small nuclear ribonucleoproteins (snRNPs) and other RNA processing factors, suggesting that they are sites for assembly and/or posttranscriptional modification of the splicing machinery of the nucleus. The histone locus body (HLB) contains factors required for processing histone pre-mRNAs. As its name implies, the HLB is associated with the genes that code for histones, suggesting that it may function to concentrate processing factors at their site of action. CBs and HLBs are present throughout the interphase of the cell cycle, but disappear during mitosis. The biogenesis of CBs shows the features of a self-organizing structure.T he CB and the HLB can be considered together for several reasons. First, the canonical marker for the CB, coilin, occurs at high concentration in some HLBs. Second, CBs and HLBs are often physically associated, suggesting some type of interaction between the two. Finally, the very large CBs of the amphibian oocyte, long a favorite for studies of CB function, share properties of both HLBs and CBs. CAJAL BODIESAs the current name suggests, the CB was first described by Ramon y Cajal, the great Spanish neuroanatomist, who in 1906 shared the Nobel Prize with Camillo Golgi for studies on the cellular architecture of the nervous system. Using a silver impregnation technique, Cajal found a small round body within the nuclei of various nerve cells, which he called the accessory body (cuerpo accessorio) (Cajal 1903;Cajal 1910). His remarkable morphological studies also included observations on splicing speckles, nucleoli, and the nuclear envelope (Lafarga et al. 2009). Bodies that we now know are related to Cajal's cuerpo accessorio were discovered independently in organisms as diverse as mammals, amphibians, insects, and plants. They were given equally diverse names-coiled bodies in mouse, rat, and human cells (Monneron and Bernhard 1969), Binnenkörper or endobodies in insects (Bier et al. 1967), and nucleolus associated bodies in plants (Chamberland and Lafontaine 1993). Order was brought to this somewhat chaotic field with the discovery of a protein named coilin, after its discovery in the coiled bodies of HeLa cells Raska et al. 1991). Antibodies against coilin turned out to be good markers for coiled bodies in vertebrate cells and even cross-reacted with the nucleolus associated bodies of the pea, Pisum sativum (Beven et al. 1995). It thus became clear that homologous nuclear organelles existed in a wide range of eukaryotes ( Figs. 1 and 2). To recognize this commonality and to regularize the terminology, the name Cajal body was adopted as a general term for a nuclear body that contains coilin ). CoilinAfter its discovery in HeLa cells, coilin quickly became the signature marker for CBs in mammalian cells. Human and mouse coilin are similar in size, MW ¼ 62.6 and ...

Cajal bodies (CBs) are nuclear organelles that occur in a variety of organisms, including vertebrates, insects, and plants. They are most often identified with antibodies against the marker protein coilin. Because the amino acid sequence of coilin is not strongly conserved evolutionarily, coilin orthologues have been difficult to recognize by homology search. Here, we report the identification of Drosophila melanogaster coilin and describe its distribution in tissues of the fly. Surprisingly, we found coilin not only in CBs but also in histone locus bodies (HLBs), calling into question the use of coilin as an exclusive marker for CBs. We analyzed two null mutants in the coilin gene and a piggyBac insertion mutant, which leads to specific loss of coilin from the germline. All three mutants are homozygous viable and fertile. Cells that lack coilin also lack distinct foci of other CB markers, including fibrillarin, the survival motor neuron (SMN) protein, U2 small nuclear RNA (snRNA), U5 snRNA, and the small CB-specific (sca) RNA U85. However, HLBs are not obviously affected in coilin-null flies. Thus, coilin is required for normal CB organization in Drosophila but is not essential for viability or production of functional gametes.

Background: Comparative genomics is a powerful means of establishing inter-specific relationships between gene function/location and allows insight into genomic rearrangements, conservation and evolutionary phylogeny. The availability of the complete sequence of the chicken genome has initiated the development of detailed genomic information in other birds including turkey, an agriculturally important species where mapping has hitherto focused on linkage with limited physical information. No molecular study has yet examined conservation of avian microchromosomes, nor differences in copy number variants (CNVs) between birds.

Using immunostaining with antibodies against cohesin subunits, we show here that cohesin-enriched structures analogous to the so-called centromere protein bodies (PB) are the characteristic of galliform lampbrush chromosomes. Their centromeric location was verified by FISH with certain DNA probes. PB-like structures were used as markers for centromere localization in chicken lampbrush chromosomes. The gap predicted to be centromeric in current chicken chromosome 3 sequence assembly was found to correspond to the non-centromeric cluster of CNM repeat on the q-arm of chromosome 3; the centromere is proposed to be placed at another position. The majority of chicken microchromosomes were found to be acrocentric, in contrast to Japanese quail microchromosomes which are biarmed. Centromere cohesin-enriched structures on chicken and quail lampbrush microchromosomes co-localize with pericentromeric CNM and BglII- repeats respectively. FISH to the nascent transcripts on chicken lampbrush chromosomes revealed numerous non-centromeric CNM clusters in addition to pericentromeric arrays. Complementary CNM transcripts from both C- and G-rich DNA strands were revealed during the lampbrush stage.

The chromosomal distribution of 41-bp repeats, known as CNM and PO41 repeats in the chicken genome and BglII repeats in the Japanese quail, was analyzed precisely using giant lampbrush chromosomes (LBC) from chicken, Japanese quail, and turkey growing oocytes. The PO41 repeat is conserved in all galliform species, whereas the other repeats are species specific. In chicken and quail, the centromere and subtelomere regions share homologous satellite sequences. RNA polymerase II transcribes the 41-bp repeats in both centromere and subtelomere regions. Ongoing transcription of these repeats was demonstrated by incorporation of BrUTP injected into oocytes at the lampbrush stage. RNA complementary to both strands of CNM and PO41 repeats is present on chicken LBC loops, whereas strand-specific G-rich transcripts are characteristic of BglII repeats in the Japanese quail. The RNA from 41-bp repeats does not undergo cotranscriptional U snRNP-dependent splicing. At the same time, the ribonucleoprotein matrix of transcription units with C-rich RNA of CNM and PO41 repeats was enriched with hnRNP protein K. Potential promoters for satellite transcription are discussed.