Cux2-positive radial glial cells generate diverse subtypes of neocortical projection neurons and macroglia

Abstract

We recently published genetic lineage-tracing experiments using the Fezf2 and Cux2 loci. These experiments demonstrated that at both the clonal and population levels Fezf2(+) RGCs are multipotent and that at the population level Cux2(+) RGCs are multipotent. Here, we extend our work on the lineages of Fezf2(+) and Cux2(+) RGCs. Clonal analysis of E10.5 neocortical progenitors suggests that most, if not all, Cux2(+) and Fezf2(+) RGCs generate diverse projection neuron subtypes located throughout layers 2-6. These results support our previous conclusion that both Fezf2(+) and Cux2(+) RGCs are multipotent neocortical progenitors. This Matters Arising Response paper addresses the Gil-Sanz et al. (2015) Matters Arising paper, published concurrently in Neuron.

Figure 1

Individual E10.5 Cux2⁺ RGCs generate cortical projection neurons and macroglia located throughout cortical layers 2–6. (A) The constitutive activity of the CRE recombinase makes the Cux2-Cre allele unsuitlable for lineage analysis of neocortical RGCs. (B) Experimental methodology for lineage analysis of Cux2⁺ RGCs using the Cux2-CreER^T2 allele. (C–D) Examples of TM at E10.5, P10 Cux2⁺ RGC clones. For each clone, a lower magnification image is shown first to illustrate the position of the clone in the cerebral cortex, followed by higher magnification images of seriel sections that span the entire clone. Panels (C1), (C2) and (C3) show neurons, an astrocyte, and an oligodendrocyte found within the clone shown in (C). (E) Scatter plot of the number of cells for each of the 43 clones analyzed. (F) Quantification of the percentages of neurons and glia generated from E10.5 Cux2⁺ RGCs based upon the analysis of 43 fully reconstructed clones. (G) Quantification of the percentages of all lineage traced cells, neurons, and glia that were located in deep or upper layers. Abbreviations: CR, Cajal–Retzius cells; Ctx, cerebral cortex; DL, deep cortical layers (layers 5 and 6); Hip, hippocampus; UL, upper cortical layers (layers 2–4). Scale bars: (C, D) 500 µm, (Inserts) 250 µm.

Figure 2

Cux2⁺ RGCs generate diverse, molecularly defined subtypes of cortical projection neurons and macroglia. All images are of brain sections from P10 Cux2-CreER^T2; Ai9 (A–T) or P10 Cux2-CreER^T2; RCE-GFP (U–Z) mice that received a single tamoxifen injection at E10.5 (TM at E10.5; P10). Lineage traced neurons expressed TBR1 (A–E), DARPP32 (F–J), SATB2 (K–O), CUX1 (P–T), or CTIP2 (A–T). Panels (B–E), (G–J), (L–O),and (Q–T) show the higher maginification images of the boxed areas in panels (A), (F), (K) and (P) respectively. The arrowheads in (B–E), (G–J), (L–O) and (Q–T) point to cells that are shown in higher magnification to the right. (U–Z) E10.5 lineage-traced Cux2⁺ RGCs generated astrocytes that expressed GFAP (U–W) and oligodendrocytes that expressed OLIG2 (X–Z). (AA) Percentages of lineage-traced deep-layer and upper-layer neurons that expressed the indicated markers. Error bars represent standard deviation. Abbreviation: Ctx, cerebral cortex; Hip, hippocampus. Scale bars: (A, F, K, P) 500 µm, (E, J, O, T) 100 µm, (W, Z) 25 µm.

Figure 3

Similar to early Cux2⁺ RGCs, E10.5 Fezf2⁺ RGCs generate diverse subtypes of cortical projection neurons and glia. (A) Experimental methodology. (B–C) Two examples of clones generated from E10.5 Fezf2⁺ RGCs. For each clone, a lower magnification image is shown first to illustrate the position of the clone in the cerebral cortex, followed by higher maginification images of seriel sections that span the full clone. (D) Scatter plot of the number of cells for each of the 46 clones analyzed. (E) Quantification of the percentages of lineage-traced cells that were neurons or glia. (F) Quantification of the percentages of lineage-traced cells, neurons, and glia that were located in deep and upper cortical layers. (G) Percentages of lineage-traced deep-layer and upper-layer neurons that expressed the indicated markers. (H) Percentages of deep-layer neurons generated from E10.5 Cux2⁺ or E10.5 Fezf2⁺ RGCs that expressed combinations of either CTIP2/TBR1 or CTIP2/SATB2. Error bars represent standard deviation. Abbreviation: Ctx, cerebral cortex; Hip, hippocampus; LV, lateral ventricle. Scale bars: (A, B, C) 500 µm, (Inserts) 250 µm.

Figure 4

Retrograde labeling of the Cux2⁺ and Fezf2⁺ lineages. (A) Experimental setup. (B) Precentages of GFP⁺ cells in layer 5 or in layers 5 and 6 that are also Ctβ positive. Error bars represent standard deviation (n=2 brains for Cux2 and 6 brains for Fezf2). (C–F) Example of brain section from Cux2-CreER^T2; RCE-GFP mice that received TM at E10.5 and were injected with Ctβ at P8. Note the dense band of Ctβ labeling in layer 5. Panels (D–F) show an enlarged view of boxed region in (C). Arrowheads indicate GFP⁺ cells originating from a Cux2⁺ RGC that extend subcerebral projections. (G–J) Example of brain section from Fezf2-CreER^T2; RCE-GFP mouse that received TM at E10.5 and was injected with Ctβ at P8. (H–J) Enlarged view of boxed regions shown in G. Arrowheads indicate GFP; Ctβ double positive cells. Abbreviation: Ctx, cerebral cortex; Hip, hippocampus; LV, lateral ventricle. Scale bars: (C, G) 500 µm, (F, J) 100 µm.