All animals use Wnt growth factors for controlling cell fate decisions as the organism develops. The wingless gene (wg) encodes the Drosophila Wnt growth factor, Wingless (Wg) protein. In Drosophila, a loss of function mutation in the wingless gene causes a disruption in epidermal patterning during embryogenesis. At the end of embryogenesis, a wild type fly larva would have a cuticle pattern, produced by the epidermal cells, that consists of repeating segments that alternate between a belt of denticles and a region of naked cuticle (see image below).
Cuticle patterning on a wild type fly.
A complete loss of function mutation in the wingless gene eliminates the regions of naked cuticle that separate denticle belts, resulting in a continuous area of denticles (see image below). In both flies and humans, Wnt growth factors associate tightly with cell membranes, but they are able to control cell fate decisions at a distance from their origin points. In the fly, some mutations in the wingless gene disrupt the cell to cell movement of the protein without altering its signaling. For example, the wgNE2 mutation restricts the range of protein movement, and so is not able to control cell fates at the normal distance seen in the wild type.
Region of denticles with no naked cuticle to create proper segmentation.
The Bejsovec lab has identified two suppressors that improve the cuticle patterning of the wgNE2 mutant embryos. For my project I will be working with these suppressors to characterize how they impact the movement of the WgNE2 protein and to test whether they affect movement of the wild-type Wg protein. As a part of my project I will be doing antibody staining for the WgNE2 protein and viewing my preps using a confocal (fluorescent) microscope.
A hope that stems from my project is that these same suppressors will also have impacts on the movement of wild type Wg protein. The discovery of movements in the wild type Wingless protein could possibly lead to groundbreaking discoveries given that the Wingless growth factor is very similar to the Wnt1 growth factor in humans, which is required to pattern the central nervous system. In mice, knocking out the Wnt1 gene results in lack of development of the cerebellum, and death of the mutant embryos (to read more about this, click here) Understanding how Wnt proteins move will help us understand how our nervous system is patterned during development.
A special thanks to my principal investigator, Dr. Bejsovec, for helping me in this blog post.
Credit for the images and information below.
Dierick, H. A. & Bejsovec, A. Functional analysis of Wingless reveals a link between intercellular ligand transport and dorsal-cell-specific signaling. 10