The work presented in the thesis was carried with the aim to understand how Widerborst (Wdb) regulate planar cell polarity in Drosophila wing. In search of proteins interacting with Wdb I carried a Yeast Two Hybrid screen and identified a protein, bitesize, with tandem C2 domains in its C terminus interacting with Wdb. Wdb also interacts with btsz genetically and removal of one copy each of Wdb and btsz enhances the truncated hair phenotype observed in Wdb EMS mutants and btsz P element insertion mutants. There are at least three predicted isoforms of bitesize and loss of the btsz-II isoform is lethal. Clonal analysis of a btsz mutant, btszJ5-2, which removes the btsz II isoform resulted in truncated wing hair outgrowth. On the other hand over expression of a myc-btsz-II construct resulted in hair duplication phenotype. However, over expression of the GFP-CT is sufficient to give wing hair duplication phenotype and this hair duplication phenotype is stronger than that caused by myc-btsz-II over expression. The Myc tagged btsz-II protein shows apical localization. Though most of the protein is confined to cytoplasm, btsz-II also marks the plasma membrane. The GFP-CT construct marks the plasma membrane strongly and is enriched in the apical region. The over expression of CT domain is sufficient to give hair duplication phenotype and the strong difference observed in the localization pattern of full length btsz-II protein and GFP-CT together suggest that regulation of membrane localization of btsz through its CT region is important to regulate hair morphogenesis. As the loss of function (truncated wing hair) and gain of function (hair duplication) both affect the process of hair morphogenesis, it can be said that btsz is a positive regulator of hair morphogenesis. Since no defect in cortical polarization of Fmi was observed in cells lacking btsz-II, btsz is required for establishment of cortical domains. However with the present study it remains unknown how exactly the C2 domains might regulate hair morphogenesis and whether Wdb targets btsz for dephophorylation to PP2A catalytic subunit.

The work presented in the thesis was carried with the aim to understand how Widerborst (Wdb) regulate planar cell polarity in Drosophila wing. In search of proteins interacting with Wdb I carried a Yeast Two Hybrid screen and identified a protein, bitesize, with tandem C2 domains in its C terminus interacting with Wdb. Wdb also interacts with btsz genetically and removal of one copy each of Wdb and btsz enhances the truncated hair phenotype observed in Wdb EMS mutants and btsz P element insertion mutants. There are at least three predicted isoforms of bitesize and loss of the btsz-II isoform is lethal. Clonal analysis of a btsz mutant, btszJ5-2, which removes the btsz II isoform resulted in truncated wing hair outgrowth. On the other hand over expression of a myc-btsz-II construct resulted in hair duplication phenotype. However, over expression of the GFP-CT is sufficient to give wing hair duplication phenotype and this hair duplication phenotype is stronger than that caused by myc-btsz-II over expression. The Myc tagged btsz-II protein shows apical localization. Though most of the protein is confined to cytoplasm, btsz-II also marks the plasma membrane. The GFP-CT construct marks the plasma membrane strongly and is enriched in the apical region. The over expression of CT domain is sufficient to give hair duplication phenotype and the strong difference observed in the localization pattern of full length btsz-II protein and GFP-CT together suggest that regulation of membrane localization of btsz through its CT region is important to regulate hair morphogenesis. As the loss of function (truncated wing hair) and gain of function (hair duplication) both affect the process of hair morphogenesis, it can be said that btsz is a positive regulator of hair morphogenesis. Since no defect in cortical polarization of Fmi was observed in cells lacking btsz-II, btsz is required for establishment of cortical domains. However with the present study it remains unknown how exactly the C2 domains might regulate hair morphogenesis and whether Wdb targets btsz for dephophorylation to PP2A catalytic subunit.