Planar cell polarity: the prickle gene actsindependently on both the Ds/Ft and the Stan systems

Epithelial cells are polarised within the plane of the epithelium, forming oriented structures whose coordinated and consistent polarity (planar cell polarity, PCP) relates to the principal axes of the body or organ. In Drosophila at least two separate molecular systems generate and interpret intercellular polarity signals: Dachsous/Fat, and the \"core\" or Stan system. Here we study the prickle gene and its protein products Prickle and Spiny leg. Much research on PCP has focused on the asymmetric localisation of core proteins in the cell and as a result prickle was placed in the heart of the Stan system. Here we ask if this view is correct and how the prickle gene relates to the two systems. We find that prickle can affect, separately, both systems -- however, neither Pk nor Sple are essential components of the Ds/Ft or the Stan system, nor do they act as a functional link between the two systems.