GFAP-Positive Progenitor Cell Production is Concentrated in Specific Encephalic Regions in Young Adult Mice

Abstract

Previous genetic fate-mapping studies have indicated that embryonic glial fibrillary acidic protein-positive (GFAP⁺) cells are multifunctional progenitor/neural stem cells that can produce astrocytes as well as neurons and oligodendrocytes throughout the adult mouse central nervous system (CNS). However, emerging evidence from recent studies indicates that GFAP⁺ cells adopt different cell fates and generate different cell types in different regions. Moreover, the fate of GFAP⁺ cells in the young adult mouse CNS is not well understood. In the present study, hGFAP-Cre/R26R transgenic mice were used to investigate the lineage of embryonic GFAP⁺ cells in the young adult mouse CNS. At postnatal day 21, we found that GFAP⁺ cells mainly generated NeuN⁺ neurons in the cerebral cortex (both ventral and dorsal), hippocampus, and cerebellum. Strangely, these cells were negative for the Purkinje cell marker calbindin in the cerebellum and the neuronal marker NeuN in the thalamus. Thus, contrary to previous studies, our genetic fate-mapping revealed that the cell fate of embryonic GFAP⁺ cells at the young adult stage is significantly different from that at the adult stage.

Keywords: Astrocytes; Cell fate; GFAP; Neural stem cells; Neurons.

Fig. 1

Distribution of X-gal⁺ cells in the developing cerebrum of hGFAP-Cre/R26R double-transgenic mice. A Distribution of X-gal⁺ cells in the cerebrum at E17.5. The vast majority of X-gal⁺ cells were in the Lct, Mct, and GE. B Distribution of X-gal⁺ cells in the cerebrum at P21. Most of the X-gal⁺ cells were in the dorsal and ventral cortex and hippocampus. a–d Selected regions showing the density of X-gal⁺ cells. Lct, lateral cortex; Mct, medial cortex; GE, ganglionic eminence. Scale bars, 100 μm in A; 800 μm in B; 100 μm in a–d.

Fig. 2

Distribution of X-gal⁺ cells in the developing cerebellum of hGFAP-Cre/R26R double-transgenic mice. A X-gal staining showed the absence of X-gal⁺ cells at E12.5. B At E13.5, X-gal staining was seen in the rhombic lip (RL). C X-gal staining at E14.5. The RL and external granular layer (EGL) showed intense X-gal labeling, which also appeared at the mid-hindbrain boundary. D At E16.5, intense Cre activity was seen in the EGL. E, F X-gal staining at P21. mhb, mid-hindbrain boundary; ml, molecular layer; pcl, Purkinje cell layer; igl, internal granular layer. Scale bars, 100 μm in A–D; 25 μm in insets in B–D; 800 μm in E, and 150 μm in F.

Fig. 3

Embryonic GFAP⁺ cells mainly produce neurons in the cortex of the young adult mouse. X-gal⁺ cells were identified using double immunohistochemical staining with antibodies for BLBP (A, C) and NeuN (B, D). Most X-gal⁺ cells co-expressed NeuN (B, D), and only a few were stained with BLBP (A, C) in both the superficial and deep cortex of the dorsal forebrain. Scale bars, 10 μm in A–D; 5 μm in insets.

Fig. 4

Embryonic GFAP⁺ cells mainly produce hippocampal neurons and thalamic astrocytes in young adult mice. A A few X-gal⁺ cells co-expressed BLBP in CA1 of the hippocampus. B Nearly all the X-gal⁺ cells were positive for NeuN in CA1 of the hippocampus. C A small proportion of X-gal⁺ cells were positive for BLBP in the thalamus. D All the X-gal⁺ cells were negative for NeuN in the thalamus. Scale bars; 10 μm in A–D; 4 μm (insets in A, B); 5 μm (insets in C, D).

Fig. 5

Embryonic GFAP⁺ cells produce neurons and astrocytes, but not Purkinje cells, in the young adult mouse cerebellum. A A large proportion of X-gal⁺ cells in the ML co-expressed BLBP. B All the X-gal⁺ cells were negative for calbindin. C A small proportion of X-gal⁺ cells in the ML were immune-positive for NeuN. D Most of the X-gal⁺ cells in the IGL were positive for NeuN. Arrows indicate examples of X-gal⁺/marker⁺ cells. Scale bars, 11.3 μm in A; 22.5 μm in B; and 7.5 μm in C and D. IGL, internal granular layer; ML, molecular layer.

Fig. 6

Composition of progeny of embryonic GFAP⁺ progenitors in different encephalic regions of the mouse at P21. Note that embryonic GFAP⁺ cells mainly produce neurons, not astrocytes, in the cortex and hippocampus of the young adult mouse. However, in the thalamus, the GFAP⁺ cells do not produce neurons. D-tcx, dorsal cortex; V-tcx, ventral cortex; Hip, hippocampus; TH, thalamus.