Transplanted Clonal Neural Stem-Like Cells Respond to Remote Photic Stimulation Following Incorporation within the Suprachiasmatic Nucleus Piotr Zlomanczuk,* , † Maciej Mrugala,* Horacio O. de la Iglesia,* Vaclav Ourednik,‡ Peter J. Quesenberry,§ Evan Y. Snyder,‡ ,1 and William J. Schwartz* ,2 *Department of Neurology and §Cancer Center, University of Massachusetts Medical School, Worcester, Massachusetts 01655; †Department of Physiology, Rydygier Medical School, Bydgoszcz, Poland; and ‡Division of Neuroscience, Children’s Hospital, Departments of Neurology, Neurosurgery, and Pediatrics, Harvard Medical School, Boston, Massachusetts 02115 Received May 23, 2001; accepted November 19, 2001 Multipotent neural stem-like cells (NSCs) obtained from one brain region and transplanted to another re- gion appear to differentiate into neuronal and glial phe- notypes indigenous to the implantation site. Whether these donor-derived cells are appropriately integrated remains unanswered. In order to test this possibility, we exploited the suprachiasmatic nucleus (SCN) of the hy- pothalamus, site of a known circadian clock, as a novel engraftment target. When a clone of NSCs initially de- rived from neonatal mouse cerebellum was transplanted into mouse embryos, the cells incorporated within the SCN over a narrow gestational window that corre- sponded to the conclusion of SCN neurogenesis. Immu- nocytochemical staining suggested that donor-derived cells in the SCN synthesized a peptide neurotransmitter (arginine vasopressin) characteristic of SCN neurons. Donor-derived SCN cells reacted to light pulses by ex- pressing immunoreactive c-Fos protein in a pattern that is appropriate for native SCN cells. This region-specific and physiologically appropriate response to the natural stimulation of a remote sensory input implies that do- nor-derived and endogenous cells formed true SCN chi- meras, suggesting that exogenous NSCs engrafted to ec- topic locations can integrate in a meaningful fashion. © 2002 Elsevier Science (USA) Key Words: c-Fos; circadian rhythms; neural stem cells; neurogenesis; suprachiasmatic nucleus; trans- plantation. INTRODUCTION The search for neural stem-like cells (NSCs)—self- renewing, multipotent, primordial cells that give rise to differentiated neurons and glia— has accelerated recently with the discovery of some candidate cell pop- ulations (1). Even in adult brains, proliferating precur- sor cells have been identified in the striatal subven- tricular zone and the hippocampal (dentate) subgranu- lar zone. Clonal analyses indicate that such cells can individually generate neurons, astrocytes, and oligo- dendrocytes in vitro. Several effective strategies have been employed to isolate and propagate uncommitted cells, including their direct dissection from regions un- dergoing neurogenesis and their proliferation and ex- pansion in culture by epigenetic means with mitogens or by genetic means via the transduction of genes that interact with cell cycle proteins in a constitutive man- ner (37). A remarkable feature of these cell types is their behavior after heterotopic and/or heterochronic trans- plantation into mammalian brain. Several groups have demonstrated that NSCs— either mixed populations of freshly dissected or mitogen-expanded cells or stable clones— can engraft, migrate, and differentiate into ostensibly appropriate neuronal and glial phenotypes that normally populate an implantation site at a par- ticular window of development (3, 4, 10, 16, 20, 22, 24, 25, 28, 29, 31, 33, 34, 38). The migration and integra- tion patterns of engrafted cells correlate with regional differences in endogenous neurogenesis, and the cells differentiate in ways characteristic of the host sites. In these studies, the phenotypes assumed by the en- grafted cells have been assessed primarily by morpho- logical and immunocytochemical criteria. The im- planted cells adopt the size, orientation, and shape of native cells; form synapses with host-derived afferents (25, 28, 31, 33); project to appropriate target sites (4, 10, 24, 31, 33); and express region-specific neurotrans- mitters or marker genes (3, 4, 22, 28, 34, 38). Never- theless, despite these signs of regional integration, there has been scant evidence of true functional inte- 1 From whom reagents may be obtained: E-mail: SNYDER@ A1.TCH.Harvard.edu. 2 To whom correspondence should be addressed. E-mail: william. schwartz@umassmed.edu. Experimental Neurology 174, 162–168 (2002) doi:10.1006/exnr.2001.7857, available online at http://www.idealibrary.com on 162 0014-4886/02 $35.00 © 2002 Elsevier Science (USA) All rights reserved.