Heterokaryons are the product of cell fusion without subsequent nuclear or chromosome loss. Decades of research using Sendai-virus or polyethylene glycol (PEG)-mediated fusion in tissue culture showed that the terminally differentiated state of a cell could be altered. But whether stable non-dividing heterokaryons could occur in animals has remained unclear. Here, we show that green fluorescent protein (GFP)-positive bone-marrow-derived cells (BMDCs) contribute to adult mouse Purkinje neurons through cell fusion. The formation of heterokaryons increases in a linear manner over 1.5 years and seems to be stable. The dominant Purkinje neurons caused the BMDC nuclei within the resulting heterokaryons to enlarge, exhibit dispersed chromatin and activate a Purkinje neuron-specific transgene, L7-GFP. The observed reprogrammed heterokaryons that form in brain may provide insights into gene regulation associated with cell-fate plasticity.
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We thank K. Koleckar for her excellent technical support and R. Doyonnas, M. LaBarge, A. Okada, F. Rossi and M. Springer for useful comments. We also thank M. Yuzaki for the generous gift of the L7-pcp-2 transgenic mice. This work was supported by a fellowship from the Wenner-Gren Foundation, Sweden, to C.B.J. and a National Institutes of Health grant AG20961 to J.M.W. and H.M.B. and NIH grants AG09521, HL65572, HD18179, Ellison Medical Foundation grant AG-33-0817, the McKnight Endowment Fund and the Baxter Foundation to H.M.B.
The authors declare no competing financial interests.
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