PT  - JOURNAL ARTICLE
AU  - José Casal
AU  - Beatriz Ibáñez-Jiménez
AU  - Peter A. Lawrence
TI  - Planar Cell Polarity: What Does The <em>prickle</em> Gene Do?
AID  - 10.1101/212167
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 212167
4099  - http://biorxiv.org/content/early/2017/10/31/212167.short
4100  - http://biorxiv.org/content/early/2017/10/31/212167.full
AB  - Many, if not all, epithelial cells are polarised within the plane of the epithelium and some form oriented structures whose coordinated and consistent polarity (planar cell polarity, PCP) relates to the principal axes of the body or organ. PCP depends on intercellular communication of polarity signals; in Drosophila at least two separate molecular systems generate these signals: Dachsous/Fat, Ds/Ft and the core or Stan system and both are conserved widely (reviewed in Butler and Wallingford, 2017). Here we make a new attempt to understand the PCP gene prickle (pk) and its products Pk and Sple. Much research on PCP has asked how and why many PCP proteins, including Pk and Sple, are asymmetrically localised in the cell (Strutt and Strutt, 2009). This question led to the pk gene being placed at the heart of the core or Stan system (Tree et al., 2002b). Here we use direct genetic tests to ask if this view is correct and if and how the pk gene relates to the Stan and the Ds/Ft systems. We conclude that Pk and Sple have been widely misunderstood: we find they can affect, separately, the Ds/Ft system (reversing, or rectifying the polarity of its output) and the core or Stan system (being required for the asymmetrical distribution of its proteins). In the Stan system they appear to work via binding to Vang. Neither Pk nor Sple are essential components of either the Ds/Ft or the Stan systems nor do they act as a bridge between the two systems.