Planar polarity in different model organisms

What constitutes a "planar polarity protein"?

These days a lot of proteins are said to be "planar polarity" proteins.

By this, people in the field, mean that a particular protein is required to estabilsh or maintain the planar polarity of a tissue. Lets get this straight. Just because a lack of a particular protein results in, for example, messed up Drosophila wing hairs or ommatidia, it does not necessarily mean that that particular protein is involved in establishing or maintaining the planar polarity of that tissue.

There are many ways in which wing hairs or ommatidia can become disrupted, for example by disrupting the actin cytoskeleton or endocytosis. This can result in general cellular defects and these cells are usually sick, perhaps dying, as other cellular processed are disrupted. This can lead to cellular defects such as disrupted polarity, but it is not a specific effect.

But what can suggest that a protein is required specifically for establishing and maintaining "planar polarity"?

The establishment of planar polarity

The field of "planar polarity" can be a minefield. This database was created to improve understanding by gathering together current knowledge. The database should make it easier to compare new findings against previous results in the field.