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Cyclic changes in amphibian egg microvilli occur during the division cycle: implication of MPF
1Laboratoire d'Immunologie Comparée, Université Pierre et Marie Curie, CNRS UA 1135, Paris, France.
Abstract:
The microvilli (MV) of Pleurodeles (amphibian) eggs were examined following fertilization and compared with those of artificially activated eggs and enucleated eggs using scanning and transmission electron microscopy. The MV pattern in fertilized eggs was found to undergo a cyclic transformation during the course of the first few division cycles. Similar changes also occurred in the MV of artificially activated eggs and enucleated eggs. The reorganization of the MV was sensitive to cycloheximide and cytochalasin B, but was unaffected by colchicine. Thus, this MV alteration requires protein synthesis and microfilaments but microtubules are not implicated in this process. In addition, the effects on the MV pattern of the maturation or mitosis promoting factor (MPF) were tested. Injection of MPF into eggs at different times during the first division cycle nearly always induced an elongation of the MV. This observation suggests that MPF could regulate either directly or indirectly, via a MPF-sensitive factor, the cyclic transformation of amphibian egg MV.
Insights
Amphibian egg microvilli undergo cyclic changes during early development. These microvilli alterations require protein synthesis and microfilaments, and are regulated by maturation promoting factor (MPF).
Area of Science:
- Cell Biology
- Developmental Biology
- Amphibian Embryogenesis
Background:
- Microvilli (MV) on amphibian eggs exhibit dynamic changes.
- Understanding the regulation of these MV transformations is crucial for comprehending early embryonic development.
Purpose of the Study:
- To investigate the cyclic transformation of microvilli in Pleurodeles eggs.
- To determine the molecular mechanisms and factors regulating MV reorganization during early cell divisions.
Main Methods:
- Scanning and transmission electron microscopy were used to examine egg microvilli.
- Experiments involved fertilized, artificially activated, and enucleated eggs.
- Pharmacological agents (cycloheximide, cytochalasin B, colchicine) and maturation promoting factor (MPF) injection were employed.
Main Results:
- Microvilli patterns cyclically transformed in fertilized, activated, and enucleated eggs.
- MV reorganization was inhibited by cycloheximide and cytochalasin B, indicating dependence on protein synthesis and microfilaments.
- Colchicine did not affect MV alteration, suggesting microtubules are not involved.
- MPF injection induced MV elongation, suggesting its regulatory role.
Conclusions:
- Amphibian egg microvilli undergo cyclic transformations regulated by protein synthesis and microfilaments.
- Microtubules are not implicated in this microvilli reorganization process.
- Maturation promoting factor (MPF) likely plays a key role in regulating these cyclic microvilli changes.