 Similar to Cajal bodies are Gemini of Cajal bodies , or gems , whose name is derived from the Gemini constellation in reference to their close " twin " relationship with CBs . Gems are similar in size and shape to CBs , and in fact are virtually indistinguishable under the microscope . Unlike CBs , gems do not contain small nuclear <unk> ( <unk> ) , but do contain a protein called survival of motor <unk> ( SMN ) whose function relates to <unk> <unk> . Gems are believed to assist CBs in <unk> <unk> , though it has also been suggested from microscopy evidence that CBs and gems are different manifestations of the same structure . Later <unk> studies have shown gems to be twins of Cajal bodies with the difference being in the coilin component ; Cajal bodies are SMN positive and coilin positive , and gems are SMN positive and coilin negative . 
