We have isolated the vertebrate homologs (fjx1) of the Drosophila
four-jointed (fj) gene from human, mouse, chicken, xiphophorus and zebrafish.
The gene is specifically expressed in several embryonic tissues like somites,
limbs and neural structures (see paper 1
and 2).
Genetic evidence suggested that the Fjx1 protein is a secreted ligand for an as
yet unknown receptor. An alternative scenario predicts Fjx1 to function in the
Golgi aparatus.
We are characterizing fjx1 function by gene knockout in the mouse and biochemical characterization of Fjx1. This includes
the search for binding sites and comparative expression analysis with markers
from the planar cell polarity pathway (Rock et al.,
2005a).
A comprehensive expression analysis of mouse dachsous and fat homologs
supports the idea that fjx1 may participate in mammalian planar cell polarity
(PCP) signalling (Rock et al.,
2005b).
This is further supported by the genetic interaction of fjx1 with other PCP
genes in mouse cystic kidney development (Saburi et al.,
2008).
Fjx1 is also part of the machinery regulating neuronal dendrite extension
(Probst et al.,
2007)