Fig. 5.

Nucleolar presence of the RNA-binding protein LARP7 in forebrain neurons. A–F, LARP7 immunofluorescence in P7 rat brain sections that were cut through the dorsal hippocampus; co-stainings with neuronal- or nucleolar markers are shown as indicated; DNA was counterstained with Hoechst-33258; in D, LARP7 antibody was replaced by control rabbit IgG. Representative micrographs of cells from the neocortical layer V (A–D) and the hippocampal field CA1 (E–F, the pyramidal layer) are shown. Both nuclear and nucleolar signals of LARP7 are visible in neurons from each region. G–J, LARP7 Immunostaining in cultured primary rat brain cells including DIV6 cortical neurons (G, J), DIV7 hippocampal neurons (H) and DIV10 astrocytes (I). Note nucleolus-like staining in neurons but not astrocytes; both cell types display nuclear presence of LARP7. In J, representative nuclear profiles are shown following 6 h treatment with 0.1% DMSO (vehicle) or 1 μm ActinomycinD (ActD); magnified images of the nucleoli are shown in the insets. In vehicle-treated cells, overlapping stainings of LARP7 and fibrillarin suggest LARP7 localization to the dense fibrillar component (DFC) of the nucleolus. After transcriptional inhibition, Npm but not LARP7 or fibrillarin were released into nucleoplasm; moreover, the persistent overlap of LARP7 and fibrillarin indicates co-localization to light nucleolar caps which sequester early rRNA processing factors including snoRNAs (see text for details). The colocalization and/or separation of LARP7 and nucleolar markers was confirmed by quantitative analysis of images from panel J (supplemental Fig. S3).