Nuclear Gems and Cajal bodies, also referred to as gemini of coiled bodies and coiled bodies (respectively), are often found paired or juxtaposed in mammalian nuclei.

Cajal bodies are highly dynamic structures of 0.2-1.0 µM in diameter and the average plant or animal nucleus contains 1-10 of these bodies (reviewed in Gall, 2000). A major component of Cajal bodies is the protein p80 coilin, which can serve as a marker for these structures. Cajal bodies are believed to be involved in snRNP biogenesis and in the trafficking of snoRNPs and snRNPs, which appear to move through the Cajal body en route to nucleoli or splicing speckles (respectively) (Sleeman and Lamond 1999) . For example, the spliceosomal

U1, U2, U4/U6 and U5 snRNPs localise to these bodies, as well as the U7 snRNP involved in histone 3'-end processing. The U3 and U8 snoRNPs, involved in pre-rRNA processing, also localise to Cajal bodies (Gall, 2000). In addition, several gene loci, including histone, U1, U2 and the U3 genes appear to associate preferentially with these structures (Matera, 1999) .

Cajal bodies and Disease

Cajal bodies have been implicated in disease by the association of the spinal muscular atrophy disease gene product, survival of motor neurons (SMN), with both Cajal bodies and nuclear gems (Carvalho et al., 1999). SMN and an associated protein SIP1 form a complex that plays an essential role in cytoplasmic snRNP biogenesis (Fischer et al., 1997), which suggests that defects in spliceosomal snRNP assembly may be central to the development of spinal musclular atrophy.

Gems, are often found coincident with or juxtaposed to Cajal bodies (depending on the cell line studied) and have been characterised by their association with the proteins SMN and gemin2 (Matera, 1999) . Interestingly, a recent study of multiple tissues, indicates that many mammalian cell types lack both gems and Cajal bodies (e.g., cardiac and smooth muscle, blood vessels, stomach, and spleen), suggesting that neither subnuclear structure is absolutely required for RNA splicing and that they may represent storage sites or reservoirs of RNA processing factors and snRNPs. (Young et al., 2000)


  • Published Movies of Cajal body dynamics
    MBC 10:2297 The Movement of Coiled Bodies Visualized in Living Plant Cells by the Green Fluorescent Protein". K Boudonck et al. (1999).

    JCB 151:1561 In Vivo Analysis of Cajal Body Movement, Separation, and Joining in Live Human Cells. M. Platani et al. (2000).

  • Lamond lab Cajal body images and movies
    -Images of Cajal body localisation
    -Images of gem localisation
    -Dynamic Cajal bodies movie
    -Phosphorylation dependent localisation of p80-coilin images from the Lamond lab (shows accumulation of coilin in the nucleolus upon okadaic acid treatment).

  • An overview of spinal muscular atrophy by Jenny Versnel


    REFERENCES

    Carvalho T, Almeida F, Calapez A, Lafarga M, Berciano MT, Carmo-Fonseca M. (1999) The spinal muscular atrophy disease gene product, SMN: A link between snRNP biogenesis and the Cajal (coiled) body. J Cell Biol 147(4):715-728

    Fischer U, Liu Q, and Dreyfuss G. (1997)The SMN-SIP1 complex has an essential role in spliceosomal snRNP biogenesis. Cell 90(6):1023-1029

    Gall, J. G. (2000) Cajal bodies: the first 1000 years. Annu. Rev. Cell Dev. Biol. 16:273-300

    Matera, A.G. (1999) Nuclear bodies: multifaceted subdomains of the interchromatin space. Trends Cell Biol. 9(8):302-309

    Sleeman JE, and Lamond AI. (1999) Newly assembled snRNPs associate with coiled bodies before speckles, suggesting a nuclear snRNP maturation pathway. Curr. Biol. 9(19):1065-1074

    Spector, D.L. (2001) Nuclear domains. J. Cell Sci. 114 (16):2891-2893

    Young PJ, Le TT, thi Man N, Burghes AH, and Morris GE. (2000) The relationship between SMN, the spinal muscular atrophy protein, and nuclear coiled bodies in differentiated tissues and cultured cells. Exp. Cell Res.256(2):365-374