Planar Cell Polarity Effector Fritz Interacts with Dishevelled and Has Multiple Functions in Regulating PCP.

The Planar cell Polarity Effector (PPE) genes , , and are downstream components in the signaling pathway, and their function is instructed by upstream Planar Cell Polarity (PCP) core genes such as and PPE proteins accumulate asymmetrically in wing cells and function in a protein complex mediated by direct interactions between In and Frtz and In and Fy. How the PCP proteins instruct the accumulation of PPE protein is unknown. We found a likely direct interaction between Dishevelled and Fritz and Dishevelled and Fuzzy that could play a role in this. We previously found that mild overexpression of rescued a weak allele. To determine if this was due to extra Frtz stabilizing mutant In or due to Frtz being able to bypass the need for In we generate a precise deletion of the gene ( ). We found that mild overexpression of Fritz partially rescued , indicating that has In independent activity in PCP. Previous studies of PPE proteins used fixed tissues, and did not provide any insights into the dynamic properties of PPE proteins. We used CRISPR/Cas9 genome editing technology to edit the gene to add a green fluorescent protein tag. provides complete rescue activity and works well for imaging. Our data showed that Fritz is very dynamic in epidermal cells and preferentially distributed to discrete membrane subdomains ("puncta"). Surprisingly, we found it in stripes in developing bristles.