| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2004: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2003: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
A Ca^<2+>/Mg^<2+>-dependent, Zn^<2+>-sensitive endonuclease activity appears in C2C12 myoblasts during myogenic differentiation. The enzymatic properties of the inducible DNase were found to be quite similar to those of DNase I-family DNases. RT-PCR analysis revealed that the induction of DNase γ, a member of the DNase I-family DNases, is correlated with the appearance of inducible DNase activity. The role of DNase γ in myoblast apoptosis was evaluated by the antisense-mediated down-regulation of DNase γ, and revealed that DNase γ is the endonuclease responsible for DNA fragmentation in apoptosis associated with myogenic differentiation. We next investigate the roles of two apoptotic endonucleases, CAD and DNase γ, in neuronal apoptosis. High expression of CAD, but not DNase γ, is detected in proliferating N1E-115 neuroblastoma cells, and apoptotic DNA fragmentation induced by staurosporine under proliferating conditions is abolished by the expression of a caspase-resistant form of ICAD. After the induction of neuronal differentiation, CAD disappearance and the induction of DNase γ occur simultaneously in N1E-115 cells. Apoptotic DNA fragmentation that occurs under differentiating conditions is suppressed by the down-regulation of DNase γ caused by its antisense RNA. The induction of DNase γ is also observed during neuronal differentiation of PC12 cells, and apoptotic DNA fragmentation induced by NGF deprivation is inhibited by the antisense-mediated down-regulation of DNase γ. These observations suggest that DNA fragmentation in neuronal and muscle cellular apoptosis is catalyzed by either CAD or DNase γ depending on the differentiation state.
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