Motoneurons (MNs) in the cervical spinal cord of the chicken embryo undergo programmed cell death (PCD) between embryonic day (E) 4 and E5. The intracellular molecules regulating this early phase of PCD remain unknown. Here we show that introduction of Bcl-2 by a replication-competent avian retroviral vector prevented MN degeneration at E4.5, whereas the expression of the green fluorescent protein (GFP) was ineffective. Bcl-2 expression did not affect the number of Islet-1/2-positive MNs at the onset of cell death (E4). However, when examined at the end of the cell death period (E5.5), the number of Islet-1/2-positive MNs was clearly increased in Bcl-2-transfected embryos compared with control and GFP-transfected embryos. Activation of caspase-3, which is normally observed in this early MN death, was also prevented by Bcl-2. Thus, MNs in the cervical spinal cord appear to use intracellular pathway(s) for early PCD that is responsive to Bcl-2.
Copyright 2002 Wiley Periodicals, Inc.