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Apical Constriction

Apical constriction is a fundamental cellular process that plays a crucial role in morphogenesis, the biological process that causes an organism to develop its shape. This process involves the contraction of the apical side of epithelial cells, leading to changes in cell shape and tissue structure. Apical constriction is essential for various developmental processes, including gastrulation, neural tube formation, and organogenesis.

Mechanism

The mechanism of apical constriction involves the coordinated action of the cytoskeleton, particularly the actin and myosin networks. The apical surface of the cell contracts due to the interaction between filamentous actin and myosin motor proteins, which generate contractile forces. These forces are regulated by signaling pathways that control the assembly and disassembly of actin filaments and the activation of myosin.

Actin and Myosin Interaction

In apical constriction, filamentous actin is organized into a network at the apical surface of the cell. Myosin II, a motor protein, interacts with this actin network to produce contractile forces. The contraction is driven by the ATP-dependent sliding of myosin along actin filaments, which shortens the apical surface and leads to cell shape changes.

Role of Rho GTPases

Rho GTPases, such as RhoA, play a critical role in regulating the actin-myosin network during apical constriction. These molecular switches activate downstream effectors that promote actin polymerization and myosin activation, facilitating the contraction of the apical surface.

Biological Significance

Apical constriction is vital for several developmental processes:

• Gastrulation: During gastrulation, apical constriction helps drive the invagination of epithelial sheets, forming the three germ layers: ectoderm, mesoderm, and endoderm.
• Neural Tube Formation: In neural tube formation, apical constriction contributes to the bending and closure of the neural plate, a critical step in the development of the central nervous system.
• Organogenesis: Apical constriction is involved in shaping organs by driving the folding and invagination of epithelial tissues.

Research and Applications

Understanding apical constriction has implications in developmental biology and medicine. Disruptions in this process can lead to developmental disorders and congenital malformations. Research into the molecular mechanisms of apical constriction can provide insights into tissue engineering and regenerative medicine.

Related Pages

• Morphogenesis
• Cytoskeleton
• Gastrulation
• Neural tube

Gallery

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  Illustration of apical constriction in epithelial cells.

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  Diagram showing the cellular changes during apical constriction.

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  Mechanisms of apical constriction with actin and myosin.

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  Stages of apical constriction in tissue morphogenesis.

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  Mace of nutmeg

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  Litchi chinensis

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  Taxus baccata