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BMP-2/-4 mediate programmed cell death in chicken limb buds
Y Yokouchi1, J Sakiyama, T Kameda
1Department of Molecular Biology, School of Science, Nagoya University, Furo-cho, Chikusa-ku, Japan.
Abstract:
During limb development, the mesenchymal cells in restricted areas of limb bud, anterior necrotic zone, posterior necrotic zone, opaque zone and interdigital necrotic zones, are eliminated by programmed cell death. The transcripts of bone morphogenetic protein (Bmp)-2 and -4 were first detected in the areas where cell death was observed, then showed overlapping expression with the programmed cell death zones except the opaque zone. To investigate the function of BMP-2 and BMP-4 during limb pattern formation, the dominant negative form of BMP receptor was overexpressed in chick leg bud via a replication-competent retrovirus to block the endogenous BMP-2/-4 signaling pathway. This resulted in excess web formation at the anterior and posterior regions of limb buds in addition to marked suppression of the regression of webbing at the interdigital regions. Significant reductions in the number of apoptotic cells in these three necrotic zones were found in the limb buds which received the virus carrying dominant negative BMP receptor. This indicates that extra tissue formation is due to suppression of programmed cell death in the three necrotic zones. Moreover, BMP-2/-4 protein induced apoptosis of mesenchymal cells isolated from the interdigital region in vitro. Other TGFbeta family proteins as TGFbeta1 and Activin did not show this effect. These results suggest that BMP-2 and BMP-4 are the apoptotic signal molecules of the programmed cell death process in the chick limb buds.
Insights
Bone morphogenetic proteins (BMPs)-2 and -4 induce programmed cell death during chick limb development. Blocking BMP signaling prevents cell death, leading to excess webbing, indicating BMPs regulate limb patterning via apoptosis.
Area of Science:
- Developmental Biology
- Molecular Biology
- Cell Biology
Background:
- Programmed cell death is crucial for limb development, eliminating mesenchymal cells in specific necrotic zones.
- Bone morphogenetic proteins (BMPs)-2 and -4 transcripts are detected in these cell death areas, suggesting a role in apoptosis.
Purpose of the Study:
- To investigate the function of BMP-2 and BMP-4 in limb pattern formation and programmed cell death during chick limb development.
- To determine if BMP-2 and BMP-4 act as apoptotic signals in limb development.
Main Methods:
- Overexpression of a dominant-negative BMP receptor in chick leg buds using a retrovirus to inhibit BMP signaling.
- Analysis of cell death and webbing formation in treated limb buds.
- In vitro apoptosis assays using isolated mesenchymal cells and BMP-2/-4 proteins.
Main Results:
- Inhibition of BMP signaling led to suppressed regression of webbing in interdigital regions and excess webbing formation in anterior and posterior regions.
- A significant reduction in apoptotic cells was observed in necrotic zones of limb buds with inhibited BMP signaling.
- BMP-2/-4 proteins induced apoptosis in isolated mesenchymal cells, while TGFbeta1 and Activin did not.
Conclusions:
- BMP-2 and BMP-4 signaling are essential for programmed cell death in chick limb necrotic zones.
- BMP-2 and BMP-4 act as specific apoptotic signal molecules regulating limb patterning through cell death.