In this report, we present the isolation and identification of a zebrafish homolog of the winged helix\forkhead transcription factor Foxj1. Foxj1 was identified in other species but not in zebrafish. Foxj1 was shown in mice to be required in ciliogenesis and left-right asymmetry establishment. Here we present a spatio-temporal expression pattern of zebrafish foxj1, showing that this gene is expressed in dorsal forerunner cells, Kupffer's vesicle, the floor plate, pronephric ducts and kidney. This expression pattern is overlapping but different from that of the foxj1.2, the closest related gene in zebrafish. Foxj1 in zebrafish appears to have similar functions as those reported in other species connected to ciliogenesis and left-right asymmetry.
KEY WORDS: Foxj1, Foxj1.2, dorsal forerunner cell, Kupffer's vesicle, floor plate, pronephric ductHepatocyte nuclear factor-3 (HNF-3)/forkhead homologue 4 (HFH-4)/Foxj1 is a winged helix/forkhead transcription factor. A 100-amino-acid DNA-binding motif, known as the winged helix, was first identified in mammalian hepatocyte nuclear factor-3 (HNF-3) and Drosophila Forkhead transcription factors (Avraham et al., 1995;Lai et al., 1993). Subsequently, many additional proteins containing the winged helix motif have been identified (Avraham et al., 1995). In humans (Pelletier et al., 1998) rats (Hackett et al., 1995) and mice, Foxj1 is expressed in ciliated cells of various tissues including the respiratory tract, brain, and ependyma in late development through adulthood, as well as in oviduct, testis, embryonic kidney (Blatt et al., 1999;Brody et al., 2000;Tichelaar et al., 1999a;Tichelaar et al., 1999b) and the choroid plexus (Blatt et al., 1999;Brody et al., 1997;Lim et al., 1997;Swetloff and Ferretti, 2005).Foxj1 is involved in the regulation of ciliogenesis and axonemal structural proteins. Foxj1 regulates basal body anchoring to the cytoskeleton of ciliated pulmonary epithelial cells, and is required for apical localization of ezrin and the formation of axonemal structures (Gomperts et al., 2004;Gomperts et al., 2007). Further, Foxj1 promotes RhoA-mediated apical actin enrichment required for ciliogenesis (Pan et al., 2007). In Foxj1 null mice, classic motile type cilia with a 9+2 microtubule ultrastructure were absent in epithelial cells, resulting in defective ciliogenesis in the airways. In other organs, sensory cilia with a 9+0 microtubule pattern, such as those on olfactory neuroepithelial cells, were still present. Foxj1 is expressed in the ciliated cells of Hensen's node in the Int. J. Dev. Biol. 52: 985-991 (2008)