Document Type

Open Access Thesis

Embargo Period


Degree Program

Molecular & Cellular Biology

Degree Type

Master of Science (M.S.)

Year Degree Awarded


Month Degree Awarded



Examples of asymmetric organs are found throughout the animal kingdom. Whether it is superficial like the fiddler crab’s claw or within an organism like our visceral organs, asymmetries have repeatedly evolved in nature. However, the genetic and developmental origins for asymmetric organ development remain unclear, especially for superficially paired structures. Within zebrafish, a striking example of asymmetry occurs within the ace/fgf8 mutant. The pharyngeal cartilages of these mutants develop asymmetrically 35% of the time, with more cartilages developing on the left or right side of the head, but the origins of this asymmetry are unknown. A significant proportion of mutants also exhibit situs inversus, whereby the visceral organs develop on the opposite side of the body. Here we seek to understand the temporal window most sensitive to giving rise to this asymmetry, and to understand if there is a correlation between the developing heart field and pharyngeal cartilage with respect to the direction of the asymmetry.

Wild type (WT) zebrafish were exposed to SU5402 during different periods of development, and heart position as well as cartilage development was observed within the developing larvae. The direction of asymmetry (i.e., left or right biased) was also recorded in ace/fgf8 mutant heart position and cartilage number to observe if there was a correlation between the two developing fields. SU5402 experiments revealed that the time window most sensitive to the development of cartilage asymmetries was during heart looping and pharyngeal arch segmentation. Furthermore, ace/fgf8 mutants exhibited a robust correlation between ventricle position and the side of cartilage asymmetry, with more cartilages forming on the side where the ventricle is located. Given the close proximity of the heart and pharyngeal cartilage fields we suggest that the heart field is influencing the developing cartilage, with signaling permeating from the developing heart to the pharyngeal mesoderm to provide a buffer on the side of the developing ventricle.

First Advisor

R. Craig Albertson

Second Advisor

Helene Cousin

Third Advisor

Rolf Karlstrom