Pitx2, a bicoid-type homeodomain transcription factor, has been implicated in Rieger's syndrome in humans and plays an important role in mediating left-right development in mice, chickens, frogs and zebrafish. It is believed that cell proliferation, cell motility as well as changes in instructive signals for cell fate in local areas are important for directing left-right asymmetry during organogenesis. As a transcription factor, Pitx2 should activate and/or repress the transcription of its target genes to execute specific cellular functions. However, little is known about the downstream targets and signaling pathways for Pitx2. I propose in this study to search for the target genes regulated by Pitx2a (one of the Pitx2 isoforms) and the relevant signaling pathways. I will use an inducible HeLa cell line ectopically expressing Pitx2a, which is already available in the laboratory. This inducible cell line will allow me to trace the downstream signaling pathways for Pitx2a based on cell phenotype and to identify the target genes for Pitx2a by comparing the RNA isolated from cells under the induced and uninduced conditions. The transgenic mouse model will also be used to assess the importance of the putative downstream target genes in mediating the function of Pitx2a in mice. Identification of these downstream target genes and signaling pathways using these cell culture and mouse model systems should allow me to make progress towards understanding of the mechanism underlying the functions of Pitx2a as well as the missing links between Pitx2a expression and its roles in morphogenesis during embryonic development.
