 Speckles are subnuclear structures that are enriched in pre @-@ messenger RNA splicing factors and are located in the interchromatin regions of the nucleoplasm of mammalian cells . At the fluorescence @-@ microscope level they appear as irregular , punctate structures , which vary in size and shape , and when examined by electron microscopy they are seen as clusters of interchromatin granules . Speckles are dynamic structures , and both their protein and RNA @-@ protein components can cycle continuously between speckles and other nuclear locations , including active transcription sites . Studies on the composition , structure and behaviour of speckles have provided a model for understanding the functional compartmentalization of the nucleus and the organization of the gene @-@ expression machinery splicing snRNPs and other splicing proteins necessary for pre @-@ mRNA processing . Because of a cell 's changing requirements , the composition and location of these bodies changes according to mRNA transcription and regulation via phosphorylation of specific proteins . The splicing speckles are also known as nuclear speckles ( nuclear specks ) , splicing factor compartments ( SF compartments ) , interchromatin granule clusters ( IGCs ) , B snurposomes . B snurposomes are found in the amphibian oocyte nuclei and in Drosophila melanogaster embryos . B snurposomes appear alone or attached to the Cajal bodies in the electron micrographs of the amphibian nuclei . IGCs function as storage sites for the splicing factors . 
