Fig. 6. Expression of srPLP and srDM20 is primarily in white matter regions of the mouse brain but is present in some neuronal populations. a,In situ hybridization of a sagittal section of a P14 mouse brain with a33P-riboprobe specific for exon 1.1 showing expression of the srPLP and srDM20 mRNAs. b,In situ hybridization of a section adjacent toa using a sense control. c, Higher magnification of a different section (counterstained with cresyl violet) showing portions of the corpus callosum and hippocampus and illustrating the punctate labeling throughout the corpus callosum and in the hippocampus below it. d, Immunohistochemical detection of srPLP and srDM20 in the corpus callosum and the hippocampus. Arrows in c andd point to cells of the size, location, and morphology of OLs that contain srPLP and srDM20 mRNAs and proteins, respectively. Unlike classic PLP and DM20 staining in the corpus callosum, srPLP and srDM20 labeling is confined to the cell somas. Also labeled are the CA2 and CA3 regions of the hippocampus.e, Higher magnification of a cerebellar region showing punctate labeling of srPLP and srDM20 mRNAs in cells throughout the white matter (redarrows) and the internal granular cell layer (whitearrows) as well as the Purkinje cells (yellowarrows). f,Immunohistochemical detection of srPLP and srDM20 in a region of the cerebellum similar to that in e. Cell bodies of OLs are indicated with redarrows, whereas Purkinje cells are indicated with blackarrows. Granule neurons located within theIGL were readily immunostained with the antibody.g, Higher magnification of the immunohistochemical detection of srPLP and srDM20 in the internal granule cell layer (openarrows) and Purkinje cells (filledarrows) from the mouse cerebellum. h, Immunohistochemical detection of srPLP and srDM20 proteins in medium-sized neurons within the anterior olfactory nucleus of the P14 mouse brain. i,Immunohistochemical control for background staining in the cerebellum with preimmune serum to the srPLP and srDM20 antibody.j–l, Primary granular neuron cultures doubly stained for srPLP and srDM20 (j;redfluorescence) and for tubulin III (k;green). l is an overlay showing that srPLP and srDM20 proteins remain associated with the neuronal cell bodies. CC, Corpus callosum; DCWM, deep cerebellar white matter; Hp, hippocampus;IC, internal capsule; IGL, internal granule cell layer.