Musashi1: An Evolutionally Conserved Marker for CNS Progenitor Cells Including Neural Stem Cells

Abstract

In situ detection of neural progenitor cells including stem-like cells is essential for studying the basic mechanisms of the generation of cellular diversity in the CNS, upon which therapeutic treatments for CNS injuries, degenerative diseases, and brain tumors may be based. We have generated rat monoclonal antibodies (Mab 14H1 and 14B8) that recognize an RNA-binding protein Musashi1, but not a Musashi1-related protein, Musashi2. The amino acid sequences at the epitope sites of these anti-Musashi1 Mabs are remarkably conserved among the human, mouse, and Xenopus proteins. Spatiotemporal patterns of Musashi1 immunoreactivity in the developing and/or adult CNS tissues of frogs, birds, rodents, and humans indicated that our anti-Musashi1 Mabs reacted with undifferentiated, proliferative cells in the CNS of all the vertebrates tested. Double or triple immunostaining of embryonic mouse brain cells in monolayer cultures demonstrated strong Musashi1 expression in Nestin(+)/RC2(+) cells. The relative number of Musashi1(+)/Nestin(+)/RC2(+) cells increased fivefold when embryonic forebrain cells were cultured to form ‘neurospheres’ in which stem-like cells are known to be enriched through their self-renewing mode of growth. Nestin(+)/RC2(–) cells, which included Tα1-GFP(+) neuronal progenitor cells and GLAST(+) astroglial precursor cells, were also Musashi1(+), as were GFAP(+) astrocytes. Young neurons showed a trace of Musashi1 expression. Cells committed to the oligodendroglial lineage were Musashi(–). Musashi1 was localized to the perikarya of CNS stem-like cells and non-oligodendroglial progenitor cells without shifting to cell processes or endfeet, and is therefore advantageous for identifying each cell and counting cells in situ.

Progenitor stem cell marker expression by pulmonary carcinomas

“…[37][38][39][40] Musashi-1 downregulates the expression of Numb protein, 11 which in turn regulates Notch receptor activity. 41 As a protein implicated in asymmetric cell division, Musashi-1 also downregulates the expression of p21 by a mechanism independent of p53.…”

Conditional Activation of Bmi1 Expression Regulates Self-renewal, Apoptosis, and Differentiation of Neural Stem/Progenitor Cells In Vitro and In Vivo

“…4V). Moreover, the expression of Musashi, another marker of undifferentiated/ uncommitted NSPC [25], was retained in a significantly higher number of cells (50% vs. 28%, p < .01) in the mutant cultures (Fig. 4N, 4O, 4V).…”

Reg I-knockout mice reveal its role in regulation of cell growth that is required in generation and maintenance of the villous structure of small intestine

“…The monoclonal mouse IgG2a antibody raised against rat Reg I, which was confirmed to cross-react to the mouse Reg I protein (Terazono et al, 1990), was employed for immunohistochemistry. Monoclonal IgG biotinylated antimouse Musashi-1 antibody (Kaneko et al, 2000) was kindly provided by Dr H Okano (Department of Physiology, Keio University School of Medicine, Tokyo, Japan). Monoclonal IgG1 anti-BrdU antibody and polyclonal anti-mouse Ki-67 antibody were purchased from DAKO (Glostrup, Denmark).…”