Necdin is expressed predominantly in postmitotic neurons and serves as a growth suppressor that is functionally similar to the retinoblastoma tumor suppressor protein. Using primary cultures of dorsal root ganglion (DRG) of mouse embryos, we investigated the involvement of necdin in the terminal differentiation of neurons. DRG cells were prepared from mouse embryos at 12.5 days of gestation and cultured in the presence of nerve growth factor (NGF). Immunocytochemistry revealed that necdin accumulated in the nucleus of differentiated neurons that showed neurite extension and expressed the neuronal markers microtubule-associated protein 2 and synaptophysin. Suppression of necdin expression in DRG cultures treated with antisense oligonucleotides led to a marked reduction in the number of terminally differentiated neurons. The antisense oligonucleotide-treated cells did not attempt to reenter the cell cycle, but underwent death with characteristics of apoptosis such as caspase-3 activation, nuclear condensation, and chromosomal DNA fragmentation. Furthermore, a caspase-3 inhibitor rescued antisense oligonucleotide-treated cells from apoptosis and significantly increased the population of terminally differentiated neurons. These results suggest that necdin mediates the terminal differentiation and survival of NGF-dependent DRG neurons and that necdin-deficient nascent neurons are destined to caspase-3-dependent apoptosis.
(c) 2002 Elsevier Science (USA).