Electron microscope tomography of Balbiani Ring hnRNP substructure.

Three-dimensional (3-D) reconstructions, by electron microscope tomography, of selectively stained, contrast enhanced Balbiani Ring (BR) hnRNP granules reveal a complex spatial arrangement of RNA-rich domains. This particulate substructure was examined by volume rendering computer graphics. Modeling the arrangement of RNA-rich domains is made difficult by apparent structural flexibility and/or heterogeneity of composition. Formulation of a consensus 3-D arrangement of RNA-rich domains will require an expanded data base of reconstructed BR granules and the development of new image manipulation and analysis techniques. This study demonstrates the potential for ultrastructural cell biology of combining several new techniques: selective nucleic acid staining, electron spectroscopic imaging to enhance contrast, electron microscope tomography and volume rendering computer graphics.