Nestin-containing cells express glial fibrillary acidic protein in the proliferative regions of central nervous system of postnatal developing and adult mice

Abstract

We are interested in the expression patterns of nestin, an embryonic intermediate filament that represent a neural precursor marker, in the mammalian central nervous system. With an immunohistochemical approach, distribution of nestin-containing cells and their colocalization with glial fibrillary acidic protein (GFAP) or neuronal nuclear specific protein (NeuN) were studied in adult and postnatal days 2–30 (P2–30) mice. Nestin-immunoreactivity was predominately distributed in certain proliferative regions, such as cerebral cortex, hippocampus, hypothalamus, subfornical organ, cerebellar cortex, area postrema, midline raphe glial structures, as well as ependymal and subependymal zones of the brain and spinal cord. The majority of nestin-immunoreactive cells, characterized by astroglial profiles of multiple and radial processes, showed a partial overlapping distribution with that of GFAP-immunoreactive astroglial cells. Double immunofluorescence confirmed that about 77% of these nestin-immunoreactive cells exhibited GFAP-immunoreactivity, indicating that a large percentage of nestin-expressing cells may have committed to astroglial cells. In developing mice, down-regulation of nestin expression was observed between P7 and P14. Although co-expression of nestin and NeuN occurred in cortical neurons of P2–7 mice, nestin-containing cells showing NeuN-immunoreactivity disappeared in CNS in older animals. Our results reveal the distribution pattern of nestin-containing neural precursors in the postnatal CNS and provide evidence on their differentiation fate to neurons and astrocytes, suggesting that nestin-containing glial cells may play an important role in remodeling and repairing in the postnatal and adult central nervous system.

Introduction

It is well documented that the expression of nestin protein in the prenatal and postnatal developing central nervous system (CNS) of mammals reflects the differentiation or proliferative state of neural precursors [6], [18], [19], [28], [36], [38], [49], [51]. Embryonic intermediate filament (IF) nestin belongs to class III IFs, which also include vimentin and glial fibrillary acidic protein (GFAP), and, structurally, it is closely related to class IV IFs, such as neurofilaments and α-internexin [9], [15], [19], [27], [28], [37]. At the embryonic neurulation stage, multipotential neural precursors or neuroepithelial precursor cells temporarily express nestin protein. Substitution of nestin protein by vimentin and GFAP or neurofilaments takes place sequentially during the maturation or differentiation of neural precursor cells. Nestin is down-regulated either at the onset of GFAP or neurofilament expression or during subsequent differentiation of multipotential neural precursor into astrocytes or neurons [6], [17], [18], [24], [27], [28], [31], [36], [37], [51]. The transient abundant expression of embryonic intermediate filament nestin is extensively recognized as a marker for multipotential neural precursor cells in developing CNS of mammals [6], [20], [22], [25], [28], [32], [41], [43].

Previous evidence has shown that nestin protein is abundantly expressed in proliferative regions of embryonic or developing CNS, and is also predominately localized in the radial glial cells that are recognized as neural precursors [6], [13], [27], [29], [32], [34], [38], [50], [52]. Furthermore, re-expression of nestin was reported to occur in traumatic brain injury, ischemic or excitotoxic cerebral lesions, as well as pathologically deafferented target regions [2], [5], [8], [21], [30], [39], [44], [45]. Significant up-regulation of nestin was also demonstrated in reactive astrocytes after systemic administration of the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) [4]. Re-expression of nestin in astroglial cells of adult is thus recognized as a sensitive marker for activation of astroglial cells in the CNS. It implies that, to certain extent, these cells expressing nestin reflect their reiterating or sustaining active state of embryonic precursor cells, and may implicate in the neurogenesis, remodeling and repairing processes of developing and adult CNS [12], [25], [35], [42], [43], [45]. Though in situ hybridization was carried out for the localization of nestin mRNA developing brain [6], the detail distribution pattern of nestin protein in adult and postnatal CNS remains to be delineated. Further studies are also needed to characterize the precursor property of nestin-expressing cells and their differentiation fate. In the present study, immunocytochemical approach was utilized to demonstrate the expression patterns of nestin protein, and its co-expression with GFAP or neuronal nuclear specific protein (NeuN) within the brain and spinal cord of adult and postnatal mice.