Neural stem cells from mouse forebrain are contained in a population distinct from the ‘side population’

Abstract

Developing and adult forebrains contain neural stem cells (NSCs) but no marker is available to highly purify them. When analysed by flow cytometry, stem cells from various tissues are enriched in a 'side population' (SP) characterized by the exclusion of the fluorescent dye Hoechst 33342. Here, we characterize the SP in embryonic, neonatal and adult forebrains, as well as in neurosphere cultures and we have determined whether this SP could be a source of enriched NSCs. By using specific inhibitors, we found that the SP from embryonic forebrain results from the activity of the ABCG2 transporter, a characteristic of other stem cells, whereas the SP from adult forebrain probably results from the ABCB1 transporter. SP cells from embryonic and adult forebrains, however, expressed a range of cell surface markers more consistent with a haematopoietic/endothelial origin than with a neural origin; NSC markers were mostly expressed on cells outside the SP (in the main population, MP). Moreover, assays for NSC growth in vitro showed that SP cells from embryonic and adult forebrains did not generate NSC-derived colonies, whereas the MP did. We thus conclude that NSCs from developing and adult forebrains are not contained in the SP contrary to stem cells from other tissues.

ABC transporters, neural stem cells and neurogenesis – a different perspective

“…Recent results show that NSCs from mouse forebrain are contained in a population distinct from the SP [134]. Moreover, other research data show that the ABCA2 transporter is widely expressed in early neural progenitors developed in vitro from ES cells [166].…”

“…Later Goodell et al [9] demonstrated that a highly enriched stem cell fraction termed SP could be isolated following Hoechst-33342 staining. Recently, ABCA3, ABCB1 and ABCG2 were found in the primitive stem cells of different tissues [129][130][131][132][133][134][135][136]. In particular, ABCB1 is expressed in human CD34+ stem cells, which can be identified by their ability to transport fluorescent dyes like Rh123 and Hoechst-33342 [128,129,[137][138][139][140][141][142][143].…”

“…In particular, ABCB1 is expressed in human CD34+ stem cells, which can be identified by their ability to transport fluorescent dyes like Rh123 and Hoechst-33342 [128,129,[137][138][139][140][141][142][143]. Interestingly, the SP phenotype in rodent and human tissues often appears to be specifically determined by the expression of an ABC transporter: for example, both ABCB1 and ABCG2 transporters are highly expressed in the SP of stem cells from different tissues such as brain, bone marrow, pancreas, liver and others, all of which can be isolated based on the cells' ability to promote the efflux of the Hoechst-33342 fluorescent dye [9,[129][130][131][132][133][134][135][136][142][143][144][145][146][147][148][149][150]. Moreover, different research teams have demonstrated that ABCA3 and ABCG2 were expressed at higher levels in SP cells than in non-SP cells in human, rhesus monkey and mouse hematopoietic tissues; and microarray analysis indicated that several genes related to stem cells were substantially upregulated in the SP cells in comparison to non-SP cells [130,151,152].…”

Maintenance of retinal stem cells by Abcg2 is regulated by notch signaling

“…The expression of Abcg2 and SP cell phenotype are also characteristics of neural stem cells, derived from different brain regions, including the retina (Hulspas and Quesenbury, 2000;Bhattacharya et al, 2003;Ahmad et al, 2004;Mouthon et al, 2006). However, little is known about the role of Abcg2 in neural stem cells and their lineage commitment.…”

The cellular and developmental biology of medulloblastoma: Current perspectives on experimental therapeutics

“…46 However, another study revealed that neural stem cells do not appear to localize to the side population in freshly harvested developing and adult murine forebrains; the side population phenotype was largely attributed to microglial and endothelial cells expressing ABCB1 and ABCG2 transporters. 47 However, the question still remains whether de-regulated neural stem cells drive the formation of brain tumors.…”