Ultrastructural characterisation of a nuclear domain highly enriched in survival of motor neuron (SMN) protein.
Mutations in the survival of motor neuron (SMN) gene are the major cause of spinal muscular atrophy (SMA). The SMN gene encodes a 38-kDa protein that localises in the cytoplasm and in nuclear bodies termed Gemini of coiled bodies (gems). When visualised by immunofluorescence microscopy, gems often appeared either in close proximity to, or entirely overlapping with coiled (Cajal) bodies (CBs) implying a possible functional relationship between these nuclear domains. With the aim of identifying subnuclear compartments corresponding to gems, we have investigated the intranuclear localisation of SMN and of its interacting protein Gemin2 by immunoelectron microscopy in cultured cells and in liver cells of hibernating dormouse. These antigens are highly enriched in round-shaped electron-dense fibro-granular clusters (EFGCs), which also display a biochemical composition similar to gems visualised by immunofluorescence microscopy. Our data reveal a novel SMN/Gemin2 containing nuclear domain and support the idea that it represents the structural counterpart of gems seen in the light microscope.
Malatesta
Manuela
M
Centre of Electron Microscopy, University of Lausanne, 1005 Lausanne, Switzerland.
Scassellati
Catia
C
Meister
Gunter
G
Plöttner
Oliver
O
Bühler
Dirk
D
Sowa
Gabriele
G
Martin
Terence E
TE
Keidel
Eva
E
Fischer
Utz
U
Fakan
Stanislav
S
D016475:3T3 Cells; D000818:Animals; D002451:Cell Compartmentation / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D020541:Coiled Bodies / Q000378:metabolism* / Q000648:ultrastructure; D017362:Cyclic AMP Response Element-Binding Protein; D003594:Cytoplasmic Granules / Q000378:metabolism / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D022781:Hepatocytes; D006801:Humans; D051379:Mice; D008854:Microscopy, Electron; D009134:Muscular Atrophy, Spinal / Q000235:genetics / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins
D017362:Cyclic AMP Response Element-Binding Protein; C108381:GEMIN2 protein, human; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; C491561:Sip1 protein, mouse