By Ryan Schablein, Biological Sciences
Advisor: Debora Sinner
Abstract: Diseases of the airway such as Tracheobronchomalacia are common conditions associated with abnormal patterning of the muscle and cartilage of the trachea. However, the underlying mechanisms of how tracheal patterning occurs is poorly understood. Wntless, is a protein that secretes Wnt ligands necessary for tracheal patterning during development. Notum is an enzyme that inactivates Wnt ligands and is essential for formation of the cartilage. While deletion of Notum primarily affects cartilage, tracheal muscle is also affected. Our goal was to compare the extent of tracheal muscle mis-patterning caused by absence of Notum at different stages of embryonic development. Methods: We utilize genetically modified mouse models wherein Notum was deleted, and smooth muscle cells were genetically labeled with GFP. Genotype of mice was determined by PCR of genomic DNA from tail clippings. Tracheal samples were visualize with fluorescent microscopy to detect GFP fluorescence in muscle cells. Results: When analyzing GFP fluorescence in muscle cells of E12, E14, and E16, of control samples exhibited an increasingly pronounced muscular patterning. The muscles cells were organized in"fibers" oriented perpendicular to the elongation axis of the trachea. In contrast, Notum deficient tracheas showed disordered patterning of the muscle cells; however the differences were only observed at late stages of tracheal development, E14 and E16 when cartilage is formed. We conclude that Notum deficient tracheas exhibit significantly less ordered tracheal muscle as development of the trachea progresses. Thus, abnormal cartilage formation secondarily affects the organization of the smooth muscle cells of Notum mice.