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Effect of microinjected N-ethylmaleimide-modified heavy meromyosin on cell division in amphibian eggs
Abstract:
N-Ethylmaleimide-modified heavy meromyosin (NEM-HMM) microinjected into amphibian eggs inhibits cytokinesis and the cortical contractions associated with wound closure. Injection of NEM-HMM into two-cell Rana pipiens embryos produces a zone of cleavage inhibition around the point of injection. Early furrows followed by time-lapse microcinematography are seen to slow and stop as they enter the NEM-HMM-injected zone. Arrested furrows slowly regress, leaving a large region of cytoplasm uncleaved. Few nuclei are found in these regions of cleavage inhibition. Wound closure is often inhibited by NEM-HMM, especially when this inhibitor is injected just beneath the egg cortex. We observe that the surface of an unfertilized Rana egg is covered with microvilli that disappear during the course of development. The surfaces of NEM-HMM-inhibited zones remain covered with microvilli and resemble the unfertilized egg surface.
Insights
N-Ethylmaleimide-modified heavy meromyosin (NEM-HMM) inhibits cell division and wound healing in frog eggs by disrupting the cytoskeleton. This disruption prevents normal cell furrowing and surface changes essential for development.
Area of Science:
- Developmental Biology
- Cell Biology
- Molecular Biology
Background:
- Cytokinesis is crucial for cell division and embryonic development.
- Cortical contractions play a role in wound closure.
- Heavy meromyosin (HMM) is a key component of the contractile apparatus in muscle and non-muscle cells.
Purpose of the Study:
- To investigate the role of N-Ethylmaleimide-modified heavy meromyosin (NEM-HMM) in inhibiting cytokinesis and cortical contractions.
- To understand the effects of NEM-HMM on amphibian egg development and wound closure.
Main Methods:
- Microinjection of NEM-HMM into amphibian eggs and early embryos.
- Time-lapse microcinematography to observe cellular processes.
- Microscopic examination of egg and embryo surface morphology.
Main Results:
- NEM-HMM injection inhibited cytokinesis, leading to uncleaved regions with few nuclei.
- Cortical contractions associated with wound closure were inhibited by NEM-HMM.
- NEM-HMM-treated zones retained microvilli, resembling unfertilized egg surfaces.
Conclusions:
- NEM-HMM disrupts the contractile machinery essential for cytokinesis and wound closure in amphibian embryos.
- The maintenance of microvilli in inhibited zones suggests a role for the contractile system in surface remodeling during development.