Dorsal radial glial cells have the potential to generate cortical interneurons in human but not in mouse brain - PubMed (original) (raw)

Dorsal radial glial cells have the potential to generate cortical interneurons in human but not in mouse brain

Xiaojing Yu et al. J Neurosci. 2011.

Abstract

Radial glial (RG) cells, in the neocortical ventricular/subventricular zone (VZ/SVZ), generate cortical projection neurons both in rodents and humans, but whether they can also generate cortical interneurons is not clear. We demonstrated both on cryosections and in cell cultures that in the human VZ/SVZ, cells can be double labeled with RG markers and calretinin (CalR) and GABA, markers that suggest interneuronal lineage. We examined in more detail the cell fate of human RG cells isolated from the VZ/SVZ at midterm. After 24 h, no CalR(+) or GABA(+) cells were seen in cultures, whereas 5-10% cells expressed Nkx2.1 and Dlx, two ventral transcription factors. CalR(+) and GABA(+) cells were apparent for the first time after 3 d in vitro, and their number increased in subsequent days, consistent with the gradual transition of RG cells into CalR(+) or GABA(+) cells. Indeed, the progeny of genetically labeled RG cells could be immunolabeled with antibodies to CalR and GABA or ventral transcription factors (Nkx2.1(+), Dlx(+)). In contrast to humans, in the embryonic mouse, similar experiments showed that only RG cells isolated from the subpallium (ganglionic eminence) generate CalR(+) or GABA(+) cells, whereas this was not the case with RG cells isolated from the pallium. These findings support the idea that human, but not mouse, dorsal RG cells have the potential to generate various subtypes of neocortical interneurons. Multiple progenitors and sites of cortical interneuron origin in human might be an evolutionary adaptation underlying brain expansion and the increased complexity of cortical circuitry in humans.

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Figures

Figure 1.

Figure 1.

The percentages of cells labeled with interneuronal markers CalR and GABA and ventral transcription factors Nkx2.1 and Dlx from human VZ/SVZ increase over time. The top diagram shows the time scale for in vitro experiments with proliferation (10 ng/ml bFGF) and differentiation (without bFGF) media. Representative images of CalR+, GABA+, Nkx2.1+, and Dlx+ cells after 4 h (A, E, I, M) and 5 div (B, F, J, N) in proliferation medium and after additional 7 div in differentiation medium (C, G, K, O). Graphs show corresponding percentages over time (D, H, L, P). Blue-nuclear bisbenzamide staining was used. *p ≤ 0.05; **p ≤ 0.001. Scale bars, A–O, 20 μm.

Figure 2.

Figure 2.

Human and mouse cryosections and cultures. A–C, Immunofluorescence of cryosections at 20 g.w. fetal brain vimentin (Vim; red) and Nkx2.1 (green) in the cortical VZ/SVZ. Inset, Higher magnification of colabeled cell. D, In the coronal section of the E16 mouse forebrain, there is a strong Nkx2.1 expression (green) in the subpallium but not in the pallium. LGE, Llateral GE; LV, lateral ventricle; Sep, septal area; Str, striatum. E, F, Higher magnification of the cortex (E) and MGE (F). G, In acute cell culture (4 h), cells isolated from the human cortical VZ/SVZ at midterm express Nkx2.1 (red). H, I, In contrast, in E16 mouse cell culture from the pallium (H), Nkx2.1 is not demonstrated, but there are numerous Nkx2.1+ cells in the subpallium culture (I, green and arrows). The dashed line in A–C represents the ventricular surface. BB, Blue bizbenzamide nuclear stain. Scale bars: A–C, G–I, 20 μm; inset, 10 μm; D–F, 50 μm.

Figure 3.

Figure 3.

Human Lex+ cells coexpress markers for radial glia and interneurons in the same cells in vitro. A–D, After 24 h in the proliferation medium, the majority of LeX+ cells are colabeled with one of the RG markers: Pax6 (A), vimentin (Vim; B), GFAP (C), or BLBP (D). E–H, After 3 div, representative images of cells double labeled with Nkx2.1 and Vim (E), Dlx and Vim (F), CalR and BLBP (G), and GABA and Vim (H) are shown. I–L, Graphs demonstrate the proportion of single- and double-labeled cells from all the cells in the above illustrated cultures after 24 h in PM and after 3 and 7 div in DM. Scale bars, A–H, 20 μm. *p < 0.05; **p < 0.001.

Figure 4.

Figure 4.

A fraction of BLBP-Cre LoxP-transfected human RG cells generate cells of the interneuron lineage after 7 div differentiation: A–C, CalR (red, arrow); D–F, GABA (red, arrow); G–I, Nkx2.1+ (red, arrow); J–L, Dlx+ (red, arrow) cells. Scale bar: (in L) A–L, 20 μm. The top diagram shows the time scale for particular in vitro experiments with proliferation (10 ng/ml bFGF) and differentiation (without bFGF) medium.

Figure 5.

Figure 5.

Mouse RG cells isolated from the forebrain at E16, transfected with BLBP-Cre LoxP and differentiated for 7 div. A–F, RG from the pallium (dorsal telencephalon) do not generate cells labeled with either CalR (A–C, red) or GABA (D–F, red). G–L, In contrast, RG cells from the subpallium (ventral telencephalon) generate cells in the interneuron lineage, CalR+ (G–I, red, arrow) and GABA+ (J–L, red, arrow) cells. Scale bar: (in L) A–L, 20 μm. The top diagram shows the time scale for particular in vitro experiments with proliferation (10 ng/ml bFGF) and differentiation (without bFGF) medium.

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