PMC

Diagram showing the cell organization in the anterior and posterior SVZ in the adult marmoset.

Cell types at the beginning of the adult RMS at the ventral anterior SVZ. A: Migrating neuroblasts (A) forming the RMS were elongated and densely packed. B: Astrocyte (B) cytoplasmic projections rich in intermediate filaments (black asterisks) ensheath neuro-blasts (A) along the RMS. Scale bars = 5 μm in A; 2 μm in B.

PSA-NCAM-positive neuroblasts in the adult OB and OT. A, B: Sagittal section of the OB. PSA-NCAM-positive cells were found in the OB core. B: Higher-magnification view of the boxed area in A. C: Sagittal section of the OT. D–F: Coronal section of the OB. Dorsal is to the left. E: Higher-magnification view of the boxed area in D. Neuroblasts were found in the core (D) and granule cell layer (F). Scale bars = 50 μm in A (applies to D); 10 μm in B (applies to C, E, F).

Neuroblasts in the adult SVZ. A–F: Distribution of PSA-NCAM-positive neuroblasts in a coronal section of the anterior forebrain. B–D: Higher-magnification views of the boxed areas in A. E,F: Distribution of PSA-NCAM-positive neuroblasts in a coronal section of the posterior forebrain. F: Higher-magnification view of the boxed area in E. G, H: Whole mount of the lateral wall of the lateral ventricle stained for PSA-NCAM. H: Higher magnification of the anterior horn, from the specimen shown in G. Scale bars = 500 μm in A, E; 25 μm in B (applies to C, D, F); 1 mm in G; 100 μm in H.

Ultrastructure of the SVZ cell types in the adult. A: Ultrastructure of the chains of migrating neuroblasts (A), surrounded by ependymal cells (E) and astrocytic processes. B: Neuroblasts (A) were elongated and showed a sparse, dark cytoplasm with cytoplasmic expansions rich in microtubules (black asterisk). The neuroblasts were surrounded by astrocytic expansions rich in intermediate filaments (white asterisks). C: Putative precursor cells were large with long processes. Inset shows a higher-magnification image of the cytoplasm, rich in microtubules, mitochondria, RER, and free ribosomes. Scale bars = 2 μm in A; 500 nm in B; 2 μm in C; 500 nm in C, inset.

Proliferation in the neonatal SVZ and OB. A–F: Coronal sections of the anterior SVZ (A, D), posterior SVZ (B, E), and OB (C, F) of a neonatal marmoset brain perfused and stained for BrdU, 2 hours after BrdU injection. D–F: Higher-magnification views of the boxed areas in A–C, respectively. G–I: Double immunofluorescence with anti-BrdU (G, magenta), anti-Mash1 (H, green), and their merged image (I). Eighty-eight percent of the BrdU-positive cells were positive for Mash1. Scale bars = 500 μm in A (applies to B, C); 25 μm in D (applies to E, F); 10 μm in G–I.

Ultrastructure of the SVZ in the adult. A: Typical layered organization of the adult SVZ. Layer I: ependyma; Layer II: hypocellular gap; Layer III: astrocyte ribbon. Inset shows a cross-section of an astrocytic expansion from the hypocellular gap layer, which contains both intermediate filaments in the center (asterisk) and microtubules in the periphery (arrows). B: Ependymal cells showed an interdigitating cytoplasm and a thin radial projection. C: Occasional electron-dense crystals were observed in the cytoplasm of ependymal cells. D: Displaced ependymal cells formed rosette-like structures that included cilia, basal bodies, and microvilli. Scale bars = 7 μm in A; 200 nm in A, inset; 2 μm in B; 0.5 μm in C; 2 μm in D.

Cell proliferation in the adult brain. A–H: BrdU-labeled cells in coronal sections of the OB (A, E), the dorsolateral aspect of the lateral ventricle (B, F), the lateral wall of the lateral ventricle (C, G), and the ventral aspect of the lateral ventricle (D, H) at 2 hours (A–D) or 1 month (E–H) after BrdU injection. I–N: Double immunofluorescence for BrdU (I, L, magenta), Dcx (J, M, green) and their merged images (K, N) showing labeled neuroblasts in the OB (I–K) and SVZ (L–N) 1 month after BrdU injection. Scale bars = 50 μm in A (applies to B–H); 10 μm in I (applies to J–N).

Light microscopy and immunohistochemistry of the neonatal RMS, olfactory tract (OT), and olfactory bulb (OB). A–C: Distribution of Dcx+ neuroblasts in a coronal section of the RMS. B,C: Higher-magnification views of the boxed areas in A. D, E: Distribution of Dcx+ neuroblasts in a sagittal section of the RMS. E: Higher-magnification view of the boxed area in D. F, G: Distribution of Dcx+ neuroblasts in a coronal section of the OT. G: Higher-magnification view of the boxed area in F. H, I: Distribution of Dcx+ neuroblasts in a sagittal section of the OT and OB. I: Higher-magnification view of the boxed area in H. J, K: Semithin section stained with toluidine blue showing the OT close to the OB. Dark cells (neuroblasts) are accumulated in the central zone of the tract. K: Higher-magnification view of the boxed area in J. The schematic drawing of a sagittal section of the neonatal marmoset brain (between C and J) shows the position of the RMS (red line) and the areas shown in D and H. Rostral is to the right. LV, lateral ventricle; CC, corpus callosum. Scale bars = 500 μm in A (applies to D, F, H); 25 μm in B (applies to C, E, G, I); 50 μm in J; 10 μm in K.

Ultrastructure of different SVZ cells in the neonate. A: Migratory neuroblasts (type A cells) in a chain (pseudocolored red) close to the ependymal cell layer and ensheathed by both astrocytic and ependymal expansions. Type A nuclei were round to oval and contained clusters of heterochromatin. B: Intermediate cell (C) between types A and B, possibly similar to mouse type C cells. These cells showed an irregular nucleus, chromatin containing small electron-dense clumps and abundant cytoplasm. An astrocyte (B) exhibiting an electron-light cytoplasm and a nucleus with lax chromatin. C: Possible neuron in contact with the ventricle through a cytoplasmic projection (pseudocolored brown). D: Axon in the ventricular lumen in contact with the ependymal surface (arrow). The axon contained dense, pleomorphic vesicles and abundant mitochondria. E: Axon in the ependymal layer (arrow), in contact with several ependymal cells. Scale bars = 5 μm in A; 2 μm in B; 5 μm in C; 1 μm in E (applies to D).

In vivo and in vitro chain migration. A: Ultrastructure of the RMS at the level of the OT. Figure shows the core of the tract, where we observed an accumulation of migratory neuroblasts (type A cells), identified by their elongated cytoplasm rich in microtubules. B: Detail of an astrocytic expansion surrounding chains of migrating neuroblasts. The astrocyte contains intermediate filaments and some RER (white asterisk). Contrast this astrocytic process with a neighboring projection from a migrating neuroblast, which contains microtubules (black asterisk). C–E: SVZ cells cultured in Matrigel for 48 hours (see also ). C: Phase-contrast image of chain-forming neuroblasts. D: The migrating cells expressed neuronal markers PSA-NCAM (green) and βIII-tubulin (magenta). E: Double immunofluorescence with anti-GFAP (green) and βIII-tubulin (magenta). Scale bars = 2 μm in A; 500 nm in B; 25 μm in C–E.

Ultrastructure of astrocytes in the adult SVZ. A: Stem cell-like astrocytes (B) in the ribbon layer. Cytoplasmic expansions from these astrocytes formed the gap layer. The astrocytes were rich in intermediate filaments. The inset shows a large nucleolus, less compact than that of other cell types, with electron-translucent areas. Beside the astrocyte, an oligodendrocyte (O) with a round, dark nucleus and scarce cytoplasm is visible. B: Structural astrocyte, located above the GAP layer and the ribbon. It contained fewer intermediate filaments. C: Astrocyte (type B1) in contact with the ventricle. D: Type B1 cells displaying a single short cilium (arrow). E: GFAP staining in a Toluidine-blue-stained semithin section showing labeled cells in the ribbon and ependymal layers. F: Immunostaining for GFAP at the ultrastructural level confirmed the labeling of astrocytic intermediate filaments (inset). B, astrocytes. Scale bars = 2 μm in A; 500 nm in A, inset; 5 μm in B,C; 1 μm in D; 10 μm in E; 2 μm in F; 200 nm in F, inset.

Light microscopy and immunohistochemistry of the neonatal SVZ. A–D: Toluidine-blue-stained semithin sections of the ventricular wall of the lateral ventricles (V). A: Smooth ventricular surface at the rostral level (indicated by the square in the inset). B: Irregular surface at the caudal level, with deep invaginations at the ventral horn (the ventral horn is indicated by the square in the inset). C: The rostral SVZ showed compact groups of small, dark cells (neuroblasts) surrounded by light cytoplasmic processes. These groups of neuro-blasts were irregularly distributed along the dorsoventral axis and formed up to 10 layers (double-headed arrow). D: The caudal SVZ was composed of 2–3 cell layers or fewer (double-headed arrow). E–G: Dorsolateral corner of the lateral ventricle stained for GFAP (E), Dlx (F), and βIII-tubulin (G). H: Distribution of Dcx-positive neuroblasts in the dorsal SVZ (coronal section). I, J: Distribution of Dcx-positive neuro-blasts in the SVZ (sagittal views). J: Higher-magnification view of the position indicated by the box in I. Inset shows the morphology of the DCX-positive cells in the boxed area in J. Scale bars = 100 μm in B (applies to A); 20 μm in D (applies to C); 25 μm in E (applies to F,G); 25 μm in H (applies to J); 500 μm in I.

MRI observation of the adult ventricles. A, B: Dorsal (A) and lateral (B) views of the 3D shape of the lateral ventricle (blue) reconstructed from serial MRI images of a postmortem marmoset brain. Anterior is to the top in A and to the left in B. C, D: High-resolution 2D T₂-weighted coronal imaging, with the first slice positioned at the anterior horn of the lateral ventricle (indicated by a yellow line in A and B) in the brain of a living marmoset. D is a higher-magnification view of the boxed area in C. Arrow indicates the small ventricular space containing cerebrospinal fluid. E: Coronal brain section stained for PSA-NCAM (from ) with an arrow indicating the ventricular space corresponding to the area in D. F: Levels of the subventricular zone studied in the adult and neonatal Callithrix jacchus brain. Left, 3D shape of the lateral ventricle (blue) reconstructed from serial MRI images of a postmortem marmoset brain. Diagrams show representative coronal sections of the three lateral ventricle levels indicated by lines a (anterior), m (medial), and p (posterior), modified from (). Scale bar = 500 μm in E (applies to A–D).

Ultrastructure of the ependymal layer in the neonate. A: Irregular cell organization in the neonatal anterior SVZ. The ependymal cells (E) formed a continuous single-cell layer of a pseudo-stratified epithelium. Astrocytic and ependymal cytoplasmic expansions formed a thin hypocellular gap layer (dashed lines). A third layer was formed by a heterogeneous cell population containing neuroblasts (A) and astrocytes (B). B: Ependymal (type E) cell in contact with the ventricle. These cells were multiciliated and displayed abundant microvilli on their apical surface. C: Randomly oriented, internalized basal bodies (arrows) without cilia, and electron-dense particles (arrowheads) in a cell undergoing ependymal differentiation. D: Electron-dense substance (asterisk) surrounded by Golgi saculi and endoplasmic reticulum (arrows) in the cytoplasm of an ependymal cell. E: Astrocyte-like (type B1) cell with a single cilium (not visible in this section) and centriole (arrowhead) in contact with the ventricular lumen through an expansion intercalated between ependymal cells (pseudocolored blue). F: Single cilium (arrow) of a different type B1 cell. This cilium is adjacent to a perpendicularly orientated centriole (arrowhead). Scale bar = 5 μm in A; 2 μm in B, E; 1 μm in C, F; 500 nm in D.