Intermediate Neuronal Progenitors (Basal Progenitors) Produce Pyramidal–Projection Neurons for All Layers of Cerebral Cortex

• Published in: Cerebral cortex (New York, N.Y. 1991) Vol. 19; no. 10; pp. 2439 - 2450
• Main Authors: Kowalczyk, Tom, Pontious, Adria, Englund, Chris, Daza, Ray A. M., Bedogni, Francesco, Hodge, Rebecca, Attardo, Alessio, Bell, Chris, Huttner, Wieland B., Hevner, Robert F.
• Format: Journal Article
• Language: English
• Published: United States Oxford University Press 01-10-2009; Oxford Publishing Limited (England)
• Subjects: Animals; Cell Count; Cerebral Cortex - embryology; Cerebral Cortex - metabolism; Eomes; Fluorescent Antibody Technique; Fluorescent Dyes; Image Processing, Computer-Assisted; In Situ Hybridization, Fluorescence; intermediate progenitor cells; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Microscopy, Video; Multipotent Stem Cells - physiology; Neurogenesis - physiology; Neurons - physiology; Pax6; radial glia; T-Box Domain Proteins - metabolism; Tbr2; Eomes; Tbr2; Pax6; radial glia; intermediate progenitor cells
• ISSN: 1047-3211; 1460-2199
• DOI: 10.1093/cercor/bhn260

The developing cerebral cortex contains apical and basal types of neurogenic progenitor cells. Here, we investigated the cellular properties and neurogenic output of basal progenitors, also called intermediate neuronal progenitors (INPs). We found that basal mitoses expressing transcription factor Tbr2 (an INP marker) were present throughout corticogenesis, from embryonic day 10.5 through birth. Postnatally, Tbr2+ progenitors were present in the dentate gyrus, subventricular zone (SVZ), and posterior periventricle (pPV). Two morphological subtypes of INPs were distinguished in the embryonic cortex, “short radial” in the ventricular zone (VZ) and multipolar in the SVZ, probably corresponding to molecularly defined INP subtypes. Unexpectedly, many short radial INPs appeared to contact the apical (ventricular) surface and some divided there. Time-lapse video microscopy suggested that apical INP divisions produced daughter INPs. Analysis of neurogenic divisions (Tis21-green fluorescent protein [GFP]+) indicated that INPs may produce the majority of projection neurons for preplate, deep, and superficial layers. Conversely, proliferative INP divisions (Tis21-GFP−) increased from early to middle corticogenesis, concomitant with SVZ growth. Our findings support the hypothesis that regulated amplification of INPs may be an important factor controlling the balance of neurogenesis among different cortical layers.