Planar cell polarity

Cartoon representation of Planar polarity in fly and mouse epithelia

Cuticular wing hair defect in Frizzled mutant flies

Planar Cell Polarity (PCP) refers to the coordinated orientation of cells within the plane of a tissue, which is orthogonal to the apical-basal axis. This cellular organization is crucial for numerous developmental processes in multicellular organisms, including the proper formation of tissues and organs. PCP is evident in a variety of organisms and tissue types, from the epithelial cells in the Drosophila wing to the vertebrate skin and inner ear. Understanding PCP is essential for comprehending how organisms develop complex structures from seemingly simple beginnings.

Overview

Planar cell polarity is a fundamental concept in developmental biology and cell biology, describing the common orientation of cells within the plane of a tissue. This polarity allows cells to perform coordinated functions that are critical for tissue structure and function. The concept of PCP is particularly important in the context of embryogenesis, where it plays a vital role in shaping the organism.

Mechanisms

The molecular mechanisms underlying PCP involve several key signaling pathways and proteins, including the Wnt signaling pathway, Frizzled receptors, and Dishevelled proteins. These components work together to establish directional cues that guide cell orientation. In Drosophila, for example, the Fat and Dachsous proteins are also crucial for PCP, acting through the Ft/Ds system. In vertebrates, additional mechanisms and molecules, such as Van Gogh-like proteins and Prickle, have been identified as important for PCP regulation.

Functions and Importance

PCP is essential for numerous developmental processes, including:

• Cell migration and cell differentiation
• Establishment of body axis and organ development
• Hair follicle orientation and skin patterning
• Orientation of cilia in the respiratory tract and kidney tubules, affecting fluid movement and filtration

Disruptions in PCP can lead to developmental defects and diseases, highlighting its importance in normal development and health.

Examples in Organisms

• In Drosophila melanogaster, PCP is evident in the uniform orientation of hairs and bristles on the wing and body.
• In vertebrates, PCP influences the alignment of hair cells in the inner ear, critical for hearing, and the orientation of heart looping, a key step in cardiac development.

Research and Applications

Research on planar cell polarity has implications for understanding congenital disorders, tissue engineering, and regenerative medicine. By elucidating the mechanisms of PCP, scientists aim to develop therapeutic strategies for conditions resulting from PCP disruptions.

See Also

• Cell polarity
• Morphogenesis
• Signal transduction