"Color Timer" mice: visualization of neuronal differentiation with fluorescent proteins
Tóm tắt
The molecular mechanisms governing the differentiation of neural stem cells (NSCs) into neuronal progenitor cells and finally into neurons are gradually being revealed. The lack of convenient means for real-time determination of the stages of differentiation of individual neural cells, however, has been hindering progress in elucidating the mechanisms. In order to be able to easily identify the stages of differentiation of neural cells, we have been attempting to establish a mouse system that would allow progression of neuronal differentiation to be visualized based on transitions between fluorescence colors by using a combination of mouse genetics and the ever-expanding repertoire of fluorescent proteins. In this study we report the initial version of such a mouse system, which we call "Color Timer." We first generated transgenic (Tg; nestin/KOr Tg) mice in which production of the fluorescent protein Kusabira-Orange (KOr) is controlled by the gene regulatory elements within the 2nd intronic enhancer of the nestin gene, which is a good marker for NSCs, so that NSCs would emit orange fluorescence upon excitation. We then confirmed by immunohistochemical and immunocytochemical analyses that the KOr fluorescence closely reflected the presence of the Nestin protein. We also confirmed by a neurosphere formation assay that the intensity of the KOr fluorescence correlated with "stemness" of the cell and it was possible to readily identify NSCs in the two neurogenic regions, namely the dentate gyrus of the hippocampus and the subventricular zone of the lateral ventricle, in the brain of adult nestin/KOr Tg mice by the orange fluorescence they emitted. We then crossed nestin/KOr mice with doublecortin-enhanced Green Fluorescent Protein Tg mice, whose immature neurons emit green fluorescence upon excitation, and it was possible to visualize the progress of NSC-to-neuron differentiation by the transition between fluorescence colors from orange to green. This two-color initial version of the "Color Timer" mouse system will provide a powerful new tool for neurogenesis research.
Tài liệu tham khảo
Shimomura O, Johnson FH, Saiga Y: Extraction, purification and properties of aequorin, a bioluminescent protein from the luminous hydromedusan, Aequorea. J Cell Comp Physiol. 1962, 59: 223-239. 10.1002/jcp.1030590302.
Prasher DC, Eckenrode VK, Ward WW, Prendergast FG, Cormier MJ: Primary structure of the Aequorea victoria green-fluorescent protein. Gene. 1992, 111: 229-233. 10.1016/0378-1119(92)90691-H.
Nowotschin S, Eakin GS, Hadjantonakis AK: Live-imaging fluorescent proteins in mouse embryos: multi-dimensional, multi-spectral perspectives. Trends in Biotechnol. 2009, 27: 266-276. 10.1016/j.tibtech.2009.02.006.
Livet J, Weissman TA, Kang H, Draft RW, Lu J, Bennis RA, Sanes JR, Lichtman JW: Transgenic strategies for combinatorial expression of fluorescent proteins in the nervous system. Nature. 2007, 450: 56-62. 10.1038/nature06293.
Gilyarov AV: Nestin in central nervous system cells. Neurosci Behav Physiol. 2008, 38: 165-169. 10.1007/s11055-008-0025-z.
Zimmerman L, Lendahl U, Cunningham M, McKay R, Parr B, Gavin B, Mann J, Vassileva G, McMahon A: Independent regulatory elements in the nestin gene direct transgene expression to neural stem cells or muscle precursors. Neuron. 1994, 12: 11-24. 10.1016/0896-6273(94)90148-1.
Kawaguchi A, Miyata T, Sawamoto K, Takashita N, Murayama A, Akamatsu W, Ogawa M, Okabe M, Tano Y, Goldman SA, Okano H: Nestin-EGFP transgenic mice: visualization of the self-renewal and multipotency of CNS stem cells. Mol Cell Neurosci. 2001, 17: 259-273. 10.1006/mcne.2000.0925.
Sunabori T, Tokunaga A, Nagai T, Sawamoto K, Okabe M, Miyawaki A, Matsuzaki Y, Miyata T, Okano H: Cell-cycle-specific nestin expression coordinates with morphological changes in embryonic cortical neural progenitors. J Cell Sci. 2008, 121: 1204-1212. 10.1242/jcs.025064.
Yamaguchi M, Saito H, Suzuki M, Mori K: Visualization of neurogenesis in the central nervous system using nestin promoter-GFP transgenic mice. NeuroReport. 2000, 11: 1991-1996. 10.1097/00001756-200006260-00037.
Karasawa S, Araki T, Nagai T, Mizuno H, Miyawaki A: Cyan-emitting and orange-emitting fluorescent proteins as a donor/acceptor pair for fluorescence resonance energy transfer. Biochem J. 2004, 381: 307-312. 10.1042/BJ20040321.
Reynolds BA, Weiss S: Clonal and population analyses demonstrate that an EGF-responsive mammalian embryonic CNS precursor is a stem cell. Dev Biol. 1996, 175: 1-13. 10.1006/dbio.1996.0090.
Couillard-Despres S, Winner B, Schaubeck S, Aigner R, Vroemen M, Weidner N, Boddahn U, Winkler J, Kuhn H-G, Aigner L: Doublecortin expression levels in adult brain reflect neurogenesis. Eur J Neurosci. 2005, 21: 1-14. 10.1111/j.1460-9568.2004.03813.x.
The GENSAT project. [http://www.ncbi.nlm.nih.gov/projects/gensat/]
Walker TL, Yasuda T, Adams DJ, Bartlett PF: The doublecortin-expressing population in the developing and adult brain contains multipotential precursors in addition to neuronal-lineage cells. J Neurosci. 2007, 27: 3734-3742. 10.1523/JNEUROSCI.5060-06.2007.
Chalfie M, Tu Y, Euskirchen G, Ward WW, Prasher DC: Green fluorescent protein as a marker for gene expression. Science. 1994, 263: 802-805. 10.1126/science.8303295.