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Movement and guidance of migrating mesodermal cells in Ambystoma maculatum gastrulae
Abstract:
A scanning electron microscopic study in early gastrulae of Ambystoma maculatum showed that migrating presumptive mesodermal cells were strongly oriented toward the animal pole. They had lamellipodia and filopodia at their leading edges, and rounded or tapering, tail-like, trailing edges. Of the cells whose polarization could be determined unequivocally, 81% appeared to be directed in a quadrant toward the animal pole, and 93% were directed to some extent away from the blastopore. This strong orientation suggests that specific mechanisms direct cell movement, in addition to the non-specific dispersive mechanism of the contact inhibition of cell movement. There is a network of fine extracellular fibrils that covers the inner surface of the ectodermal layer. Filopodia of the migrating cells frequently attach to and appear to follow the fibrils, suggesting that the fibrils serve as a guiding substratum for cell attachment and movement. There are areas where the fibrils are apparently aligned along the blastopore-animal pole axis, and a preliminary statistical analysis using micrographs at high magnification showed a significant alignment parallel to the blastopore-animal pole axis. This fibril alignment could cause the strong orientation of the mesodermal cells by means of contact guidance.
Insights
Early gastrulae of Ambystoma maculatum show oriented mesodermal cell migration toward the animal pole. Extracellular fibrils guide these cells, suggesting specific directional mechanisms beyond general cell movement inhibition.
Area of Science:
- Developmental Biology
- Cell Biology
- Embryology
Background:
- Cell migration is crucial for embryonic development.
- Understanding directed cell movement in early embryos is key to developmental processes.
- Previous studies suggested non-specific mechanisms for cell movement.
Purpose of the Study:
- To investigate the orientation of migrating mesodermal cells in early gastrulae.
- To identify potential guidance mechanisms for cell movement during gastrulation.
- To examine the role of extracellular fibrils in directing cell migration.
Main Methods:
- Scanning electron microscopy of early gastrulae (Ambystoma maculatum).
- Analysis of cell morphology, including leading and trailing edges.
- Microscopic observation and preliminary statistical analysis of cell orientation and extracellular fibril alignment.
Main Results:
- Migrating presumptive mesodermal cells showed strong orientation toward the animal pole (81%).
- Cells were predominantly oriented away from the blastopore (93%).
- Extracellular fibrils on the ectodermal layer appeared to guide cell movement, with observed alignment along the blastopore-animal pole axis.
Conclusions:
- Specific mechanisms, likely involving contact guidance by aligned extracellular fibrils, direct mesodermal cell migration.
- Cellular orientation suggests active guidance systems are involved in gastrulation.
- The findings provide insights into the physical cues governing embryonic cell movement.