Abstract
Developing classroom activities that help promote students’ ability to synthesize and evaluate mechanisms of organ formation is important for their life-long learning in the life sciences. Here, I present several techniques that engage and gauge (engauge) students in middle school science outreach and undergraduate college settings by using normal development of the zebrafish heart. The zebrafish heart is used as a scaffold for enabling students to explore how developmental principles can inform heart repair and regeneration, as well as mechanisms that underlie heart abnormalities, such as cardia bifida (split heart). These strategies set the framework for future investigations into how instructors can engage their students in the process of scientific inquiry.
Introduction
Promoting student engagement in the process of inquiry during scientific and medical investigations is crucial to equip them with life-long learning and problem-solving skills (Buskohl et al., 2012; Chiappetta, 2004; Kao, 2016). In particular, one of the challenges is how we engage our students in the molecular and cellular mechanisms involved during organ development over time and space. Within the developmental biology community, there have been useful examples, such as embryo origami (Darnell, 2008–2016; Tosney, 2004, 2008–2016), as well as other online tools and resources that help our students internalize and apply developmental concepts to organ repair (Kao, 2014; Porch et al., 2006). However, one question that remains is, how do we engage and gauge (engauge) (Handelsman et al., 2007) students in elucidating the molecular and cellular mechanisms of heart development? The zebrafish embryonic and adult heart (Kao et al., 2015; Porch et al., 2006; Yelon et al., 1999; Yelon et al., 2000) provides not only a platform for investigating the steps of heart development, but also enables students to synthesize these concepts with strategies for cardiac regeneration. As a step toward engaging students in science outreach or research lecture settings, I have created and implemented a blended set of teaching strategies to engauge student learning.
Cardiac Origami: Constructing Highlighted Stages of Zebrafish Heart Development
To engauge students in the mechanisms of heart tube formation, one strategy is to interface a heart construction activity within an HHMI heart regeneration video (Porch et al., 2006). After introducing the audience to the importance of heart physiology and heart regeneration, a slide prompts the students, whether in a science outreach or a research lecture, to work in groups or pairs to formulate mechanisms on how a heart tube is formed from cardiac cell types during zebrafish embryo development (Figure 1A–1C). In a research seminar or classroom setting, the bilateral arrangement of cardiac muscle cell types (Figure 1A) and function heart tube (Figure 1C) are shown. The timeline can be also viewed in a stepwise formation from recyclable items (Figures 2 & 3).
Highlighted steps of zebrafish heart development. (A–C) Examples of cellular steps during zebrafish embryo development to emphasize during class or research seminar. (A) Bilateral arrangement of ventricular (blue) and atrial (green) cardiomyocytes. (B) Cardiac cone formation where atrial cardiomyocytes (green) coalesce around ventricular cardiomyocytes (blue) to form cone structure. (C) Formation of cardiac chambers of the heart tube. Ventricle (blue) and atrium (green) are formed in a head-to-tail fashion along the anterior-posterior axis of the embryo.
Constructing stages of heart development from recyclable items. (A–F) Highlighted steps to reconstruct key stages during zebrafish heart development. (A) Subdivided sheet of paper marking atrial cardiomyocytes (green hashes) and ventricular cardiomyocytes (blue hashes). (B) Bilateral arrangement in “railroad track” fashion where ventricular cardiomyocytes (blue hashes, blue arrows) face each other, and atrial cardiomyocytes are on the outer ends (green hashes, green arrows). (C) Cardiac crescent formation. Ventricular cardiomyocytes (inner rim blue with hash marks) and atrial cardiomyocytes (outer rim with green hash marks). (D) Heart tube with demarcated ventricle (blue) and atrium (green) chambers. At the interface between these chambers, proepicardial clusters are first formed (purple). (E) Endocardium (magenta arrow) is constructed with a slightly smaller circumference than cardiomyocyte layer with proepicardial cells. (F) Three cell layers of heart tube are assembled, with proepicardial cells (purple), ventricle (blue), atrium (green), and endocardium (magenta arrow).
Constructing intermediate stages of cardiac muscle cell types during heart development. (A–D) Step-by-step illustrations of intermediate heart muscle chambers during zebrafish heart development that can be posted on the board. (A) Ventricular (green paper, green arrows) or atrial (magenta paper, magenta arrows) cardiac muscle cells are formed along the adjacent left and right sides of the spinal cord (yellow spinal cord origami model). (B) Cardiac crescent stage illustrating the point of fusion to form the cardiac cone (arrows). (C) Tape is used to attach the ends of the atrium and ventricle to form the cardiac cone. (D) Heart tube with demarcated ventricle (green) and atrium (magenta) chambers.
To construct the heart development origami activity, I use the following steps and recyclable items:
To construct the early stage of heart development, take two 8.5 × 11 inch pieces of used paper and color half of each sheet of paper with contrasting colors to represent atrial versus ventricular cardiac muscle cells, or cardiomyocytes (Figure 2A). These two bilateral stripes represent the lateral plate mesoderm (Figure 2B, arrows). In particular, be sure that ventricular cardiomyocytes (Figure 2B, blue arrows) are faced toward each other so that they are mirror images along the longitudinal plane of the paper.
To make the intermediate stage of heart development, take another 8.5 × 11 inch piece of used paper, and use two contrasting colors to label the inner rim as the ventricular cardiac muscle cells, and the outer rim as the atrial cardiac muscle cells (Figures 2C & 3A–3D).
Label the early proepicardial cells with purple (or another contrasting color) near the interface between the atrium and ventricle (Figure 2D, purple arrow). These types of cells give rise to the coronary vessels, cardiac fibroblast cells, and smooth muscle cells.
To make the final heart tube, take another sheet of construction paper of a contrasting color: this represents the innermost layer of the heart called the endocardium (Figure 2E, magenta arrow, & Figure 3D). Next, take another recyclable piece of paper, make one half the atrial and ventricular cardiac chambers, and wrap them into a tube. Fasten the ends with clear scotch tape.
Finally, place the inner endocardium within the cardiac heart tube with the labeled proepicardial cells (Figure 2F, arrow).
Utilizing Heart Origami Model in Different Learning Settings
Each of these models can be utilized in different ways depending on one's learning goals for a science outreach, classroom, lab, or research lecture setting. For instance, in a science outreach setting for middle or high school students, visitors and students have two learning goals: (1) Distinguish the different stages of heart development. (2) Reconstruct the stages of zebrafish heart development in the context of cardiac muscle and proepicardial cells. After introducing the importance of the zebrafish heart in tissue regeneration study, using the HHMI heart regeneration video with your own voice-over, one of the activities is to randomly hand out each of the model stages of zebrafish heart development, and have students work in groups to reconstruct the timeline of zebrafish heart development (Table 1).
For non-majors and biology majors at a college level, segments of the cardiac origami activity can be integrated within a research seminar or a classroom setting. For instance, for non-majors at Seattle University in the Genetics of Disease course in Spring 2016, one of the learning objectives was for students to evaluate the cellular mechanisms of zebrafish heart regeneration. I used a “flipped” classroom approach, and asked them the following questions for homework: After watching the video animation on zebrafish heart regeneration, what are the cellular and molecular processes involved during cardiac regeneration? How could this be applied to patients who had suffered from heart attacks? Write down all your answers.
After peer review of the homework question, I then clarify misconceptions on heart development and regeneration, and review biological concepts through instructor-led “jeopardy” questions in groups along a spectrum of Bloom's taxonomy (Bloom et al., 1956, 1971; Crowe et al., 2008). In Table 1, these group questions are cross-listed with learning objectives that are aligned to core concepts, such as structure and function from Vision and Change (AAAS, 2015). Finally, reflection questions are also included so I can see how students are synthesizing information or comparing and contrasting mechanisms of tissue regeneration in heart versus skin tissues.
In contrast, in a biology research seminar for undergraduates, I use a different blended strategy. Before describing research findings, I first pose the question: How does a set of cardiac muscle cells form a functional heart tube during zebrafish development? After students discuss their answers in small groups, I then have them report, and I summarize the mechanism(s) they had mentioned. Some examples include “cell division of cardiac cells,” “cell migration,” and “wrapping.” During the debrief, I review and summarize the steps of zebrafish heart development, and share one or two key data and findings with my audience (Table 1).
These blended strategies provide a framework for engauging students in either a science outreach or classroom/research lecture settings in the process of scientific inquiry. These provide the framework for exploring how students’ misconceptions arise in different learning settings (Crowe et al., 2008; Modell et al., 2005), and provide strategies for how we can help our students evaluate primary data and design testable hypotheses and research proposals.
Supplemental Animation
Howard Hughes Medical Institute BioInteractive Heart Regeneration link:
http://www.hhmi.org/biointeractive/zebrafish-heart-regeneration
Acknowledgments
I would like to thank Judy Barrere for bringing her middle school students during the science outreach at Seattle Children's Research Institute; faculty at Seattle University during the Spring of 2016; and discussions with colleagues at Heritage University.
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Vol. 79 No. 5, May 2017
