Focus

Using zebrafish to study development and disorders

Research

In my laboratory we are using the zebrafish to study how the left-right (LR) axis and pattern is established. Vertebrates appear bilaterally symmetric, but have internal asymmetries along the LR axis. This axis is revealed by the asymmetric placement of organs along the midline. For example, the human heart is located on the left of the body cavity, while the liver is located on the right. While genes implicated in LR patterning have been identified, we do not know how the LR axis is established, how the axis is aligned with the existing dorsal-ventral and anterior-posterior axes, or how LR information is received and interpreted by developing organs. Proper LR axis formation is critical for organogenesis as correct organ placement allows for proper connectivity with the developing vasculature. In humans, defects in LR patterning often manifest as congenital heart disease. Our current studies focus on the mechanisms of left-right patterning, and on identifying new genes involved in this process. Additionally, we use our work in zebrafish to understand human disorders including ciliopathies, RASopathies, idiopathic scoliosis and congenital heart defects.

Left-Right Patterning in the Vertebrate Embryo

Asymmetric expression of the Nodal inhibitor dand5 (magenta) in the zebrafish ciliated (green) left-right organizer.

We use the zebrafish to study how the left-right (LR) axis is established. Vertebrates appear bilaterally symmetric, but have internal asymmetries along the LR axis, as revealed by the asymmetric placement of organs. For example, the human heart is located on the left of the body cavity, while the liver is located on the right. Defects in LR patterning can lead to birth anomalies, including congenital heart defects, that are often fatal. Current models propose cilia driven flow is required to establish LR patterning, but we still lack a full understanding of how flow is translated into a signal that is understood and responded to by relevant cells to produce asymmetric gene expression in the embryo. Without a full understanding of the genes involved and the signaling pathways utilized, we are missing important information about a process that contributes substantially to congenital heart defects in humans.  Our current studies focus on identifying new players in LR patterning that will help define the pathway downstream of flow that produces asymmetric gene expression.

Selected Publications: 

• Bicc1 and Dicer regulates left-right patterning through post-transcriptional control of the Nodal inhibitor Dand5
• Gdf3 is required for robust Nodal signaling during germ layer formation and left-right patterning
• Two additional midline barriers function with midline lefty1 expression to maintain asymmetric Nodal signaling during left-right axis specification in zebrafish

Understanding how organs obtain asymmetric positions

How an organ obtains its final asymmetric position is not well understood. Organs such as the heart and pancreas form at the midline and obtain asymmetric positions later in development. Asymmetry is governed by the left-sided expression of Nodal early in development, yet each organ responds differently to this signal; for example, the heart loops to the right, while the liver is positioned on the left. To better understand how organs respond to asymmetric information, we are investigating how the developing heart responds to Nodal.  Our current studies focus on implementing genomic approaches to identify Nodal-induced transcriptomic changes that drive asymmetric organ morphogenesis.  Using confocal imaging, we take advantage of the transparency of zebrafish embryos to image asymmetric heart development in real time to better understand the collective cell movements that occur in this process. These studies additionally shed light on cell migration mechanisms that can be utilized by cancer cells to metastasize.

Selected Publications: 

• Cooperation between Nodal and FGF signaling regulates zebrafish cardiac cell migration and heart morphogenesis
• Left-right asymmetric heart jogging increases the robustness of dextral heart looping in zebrafish
• Integration of nodal and BMP signals in the heart requires FoxH1 to create left-right differences in cell migration rates that direct cardiac asymmetry

Utilizing Zebrafish as a Model to Study Human Disease 

Zebrafish are an excellent model for studying human disease, in part thanks to their genetic similarity to humans, their ability to be easily manipulated biologically and chemically, and their transparency which allows for feasible observation of disease progression. Variants of unknown significance from patient whole genome sequencing can often be rapidly evaluated in zebrafish providing information critical for correct diagnoses. We have developed models to study genes involved in ciliopathies, idiopathic scoliosis, and RASopathies. Our studies provide insights into disease mechanisms, can identify potential therapeutic targets, and can enable screening of drug libraries for novel drug interventions.

Selected Publications:            

• Abrogration of MAP4K4 protein function causes congenital anomalies in humans and zebrafish(Link is external)
• Zebrafish models of idiopathic scoliosis link cerebrospinal fluid flow defects to spine curvature(Link is external)
• Divergent effects of intrinsically active MEK variants on developmental Ras signaling(Link is external)
• In vivo severity ranking of Ras pathway mutations associated with developmental disorders(Link is external)
• The coiled-coil domain containing protein CCDC40 is essential for motile cilia function and left-right axis formation

Biography

Rebecca Burdine is a faculty member in the Department of Molecular Biology at Princeton University. Her lab focuses on understanding the developmental mechanisms that control left-right patterning and organ morphogenesis in order to understanding how structure birth anomalies arise. She was named the 44th Mallinckrodt Scholar for the Edward Mallinckrodt Jr. Foundation, and received a Scientist Development Career Award from the American Heart Association in 2003. She was elected as fellow to the American Association for the Advancement of Science (AAAS) in 2018. She is currently serving on the Board of The International Society of Differentiation, and previously served on the boards of the Genetics Society of America and the International Zebrafish Society. She is on the Editorial board for Zebrafish, and regularly serves on grant review panels for the NIH and NSF. 

Dr. Burdine graduated summa cum laude from Western Kentucky University, majoring in Recombinant Gene Technology with a minor in Chemistry. She received her Ph.D. from Yale University for her thesis work with Dr. Michael Stern. Dr. Burdine carried out her postdoctoral research in the laboratory of Alexander F. Schier (Harvard) when he was at the Skirball Institute of Biomolecular Medicine at New York University. 

Dr. Burdine is a parent to a child with Angelman Syndrome. She first served on the Angelman Syndrome Foundation (ASF) scientific advisory committee in 2007 by invitation from Dr. Joe Wagstaff. She has previously served as Chief Scientific Officer for the Pitt-Hopkins Research Foundation and for the Foundation for Angelman Syndrome Therapeutics. She is currently serving on the Board of Directors and the Chair of the Science Advisory Committee for the ASF.

Honors & Awards