Female zebrafish (Danio rerio) demonstrate stronger preference for established shoals over newly-formed shoals in the three-tank open-swim preference test.

Zebrafish (Danio rerio) share a considerable amount of biological similarity with mammals, including identical or homologous gene expression pathways, neurotransmitters, hormones, and cellular receptors. Zebrafish also display complex social behaviors like shoaling and schooling, making them an attractive model for investigating normal social behavior as well as exploring impaired social function conditions such as autism spectrum disorders. Newly-formed and established shoals exhibit distinct behavior patterns and inter-member interactions that can convey the group's social stability. We used a three-chamber open-swim preference test to determine whether individual zebrafish show a preference for an established shoal over a newly-formed shoal. Results indicated that both sexes maintained greater proximity to arena zones nearest to the established shoal stimulus. In addition, we report the novel application of Shannon entropy to discover sex differences in systematicity of responses not revealed by unit-based measurements; male subjects spent more time investigating between the two shoals than female subjects. This novel technique using established versus newly-formed shoals can be used in future studies testing transgenics and pharmacological treatments that mimic autism spectrum disorder and other disorders that affect social interaction.

Heterogeneous pdgfrb+ cells regulate coronary vessel development and revascularization during heart regeneration.

Endothelial cells emerge from the atrioventricular canal to form coronary blood vessels in juvenile zebrafish hearts. We find that pdgfrb is first expressed in the epicardium around the atrioventricular canal and later becomes localized mainly in the mural cells. pdgfrb mutant fish show severe defects in mural cell recruitment and coronary vessel development. Single-cell RNA sequencing analyses identified pdgfrb+ cells as epicardium-derived cells (EPDCs) and mural cells. Mural cells associated with coronary arteries also express cxcl12b and smooth muscle cell markers. Interestingly, these mural cells remain associated with coronary arteries even in the absence of Pdgfrß, although smooth muscle gene expression is downregulated. We find that pdgfrb expression dynamically changes in EPDCs of regenerating hearts. Differential gene expression analyses of pdgfrb+ EPDCs and mural cells suggest that they express genes that are important for regeneration after heart injuries. mdka was identified as a highly upregulated gene in pdgfrb+ cells during heart regeneration. However, pdgfrb but not mdka mutants show defects in heart regeneration after amputation. Our results demonstrate that heterogeneous pdgfrb+ cells are essential for coronary development and heart regeneration.

Insights from the Inclusive Environments and Metrics in Biology Education and Research Network: Our Experience Organizing Inclusive Biology Education Research Events.

In contrast to efforts focusing on improving inclusion in STEM classrooms from kindergarten through undergraduate (K-16), efforts to improve inclusion in scientific meetings and conferences, important hubs of STEM culture, are more recent. Markers of inclusion that are sometimes overlooked at these events can include the composition of panels, how workshops are run, the affordability of conferences, and various other mechanisms that maintain pre-existing hierarchies and norms that limit the participation of early-career researchers and individuals of minoritized cultural, linguistic, and economic backgrounds. The Inclusive Environments and Metrics in Biology Education and Research (iEMBER) network coordinates efforts of researchers from many fields interested in diversity and inclusion in biology education. Given the concerns regarding inclusion at professional meetings, iEMBER has developed and implemented several practices in planning and executing our meetings to make them more inclusive. In this report, we share our experiences developing inclusive meetings on biology education research and discuss the outcomes of such efforts. Specifically, we present our approach to planning and executing the iEMBER 2019 conference and the National Association of Biology Teachers iEMBER 2019 workshop. This report adds to the growing body of resources on inclusive meetings, provides readers with an account of how such an attempt at implementation might unfold, and complements existing theories and work relating to the importance and functioning of such meetings in terms of representation in STEM.

Connecting Theory to Practice: Using Self-Determination Theory To Better Understand Inclusion in STEM.

In the United States, persistence for women and ethnic minorities in science, technology, engineering, and math (STEM) careers is strongly impacted by affective factors such as science identity, agency, and sense of belonging. Policies aimed at increasing the diversity of the national STEM student population and workforce have recently focused on fostering inclusive learning environments that can positively impact the experiences of underrepresented minorities (URMs) in STEM, thus increasing their retention. While research on inclusion in STEM in higher education is relatively new, inclusion research has a rich history in several other disciplines. These fields have developed theoretical frameworks and validated instruments to conceptualize and assess inclusion. Self-determination theory (SDT) is a well-established theoretical framework in educational psychology that states that ones' internal motivation is strongly correlated with the satisfaction of three specific psychological needs: autonomy, competency, and relatedness. In this paper, we introduce SDT and discuss how it relates to inclusion and to ongoing efforts to increase retention of STEM URM students in higher education environments. We argue that grounding inclusion initiatives in the SDT framework increases our understanding of the mechanisms mediating their impact, thus facilitating their reproducibility and generalizability. Finally, we describe how this theoretical framework has been adapted by the field of Industrial and Organizational Psychology to define and assess inclusion in the workplace as an example of how STEM education researchers can use this framework to promote and assess inclusion in their fields.

High fidelity: Assessing zebrafish (Danio rerio) responses to social stimuli across several levels of realism.

Behavioral assays of zebrafish shoaling have recently been employed to investigate social behavior in zebrafish models of psychiatric disease. Many studies have developed simulated models of conspecifics to serve as alternatives to live shoals in order to examine specific cues that contribute to shoaling behavior. However, no studies have investigated the extent to which zebrafish prefer one stimulus over another when given the choice between two conspecific alternatives (live or simulated). In the present study, we employed a new, four-quadrant choice preference task that allowed zebrafish to swim freely between a live shoal and a motorized mobile shoal, a live shoal and playback of a video-recorded shoal, or a motorized mobile shoal and playback of a video-recorded shoal. Behavior tracking software was used to track subjects' movements in upper and lower quadrants on either side of the test arena. Subjects spent more time near the live shoal, especially in the lower quadrant, and exhibited different swim patterns in response to each simulated conspecific alternative, suggesting that zebrafish prefer a live shoal over models of lower fidelity.

PDGF signaling is required for epicardial function and blood vessel formation in regenerating zebrafish hearts.

A zebrafish heart can fully regenerate after amputation of up to 20% of its ventricle. During this process, newly formed coronary blood vessels revascularize the regenerating tissue. The formation of coronary blood vessels during zebrafish heart regeneration likely recapitulates embryonic coronary vessel development, which involves the activation and proliferation of the epicardium, followed by an epithelial-to-mesenchymal transition. The molecular and cellular mechanisms underlying these processes are not well understood. We examined the role of PDGF signaling in explant-derived primary cultured epicardial cells in vitro and in regenerating zebrafish hearts in vivo. We observed that mural and mesenchymal cell markers, including pdgfrß, are up-regulated in the regenerating hearts. Using a primary culture of epicardial cells derived from heart explants, we found that PDGF signaling is essential for epicardial cell proliferation. PDGF also induces stress fibers and loss of cell-cell contacts of epicardial cells in explant culture. This effect is mediated by Rho-associated protein kinase. Inhibition of PDGF signaling in vivo impairs epicardial cell proliferation, expression of mesenchymal and mural cell markers, and coronary blood vessel formation. Our data suggest that PDGF signaling plays important roles in epicardial function and coronary vessel formation during heart regeneration in zebrafish.

Platelet-derived growth factor receptor beta is critical for zebrafish intersegmental vessel formation.

BACKGROUND: Platelet-derived growth factor receptor beta (PDGFRbeta) is a tyrosine kinase receptor known to affect vascular development. The zebrafish is an excellent model to study specific regulators of vascular development, yet the role of PDGF signaling has not been determined in early zebrafish embryos. Furthermore, vascular mural cells, in which PDGFRbeta functions cell autonomously in other systems, have not been identified in zebrafish embryos younger than 72 hours post fertilization. METHODOLOGY/PRINCIPAL FINDINGS: In order to investigate the role of PDGFRbeta in zebrafish vascular development, we cloned the highly conserved zebrafish homolog of PDGFRbeta. We found that pdgfrbeta is expressed in the hypochord, a developmental structure that is immediately dorsal to the dorsal aorta and potentially regulates blood vessel development in the zebrafish. Using a PDGFR tyrosine kinase inhibitor, a morpholino oligonucleotide specific to PDGFRbeta, and a dominant negative PDGFRbeta transgenic line, we found that PDGFRbeta is necessary for angiogenesis of the intersegmental vessels. SIGNIFICANCE/CONCLUSION: Our data provide the first evidence that PDGFRbeta signaling is required for zebrafish angiogenesis. We propose a novel mechanism for zebrafish PDGFRbeta signaling that regulates vascular angiogenesis in the absence of mural cells.

Rac1 induces the clustering of AMPA receptors during spinogenesis.

Glutamatergic synapses switch from nonspiny synapses to become dendritic spines during early neuronal development. Here, we report that the lack of sufficient Rac1, a small RhoGTPase, contributes to the absence of spinogenesis in immature neurons. The overexpression of green fluorescence protein-tagged wild-type Rac1 initiated the formation of dendritic spines in cultured dissociated hippocampal neurons younger than 11 d in vitro, indicating that Rac1 is likely one of the missing pieces responsible for the lack of spines in immature neurons. The overexpression of wild-type Rac1 also induced the clustering of AMPA receptors (AMPARs) and increased the amplitude of miniature EPSCs (mEPSCs). The expression of constitutively active Rac1 induced the formation of unusually large synapses with large amounts of AMPAR clusters. Also, our live imaging experiments revealed that the contact of an axon induced the clustering of Rac1, and subsequent morphological changes led to spinogenesis. Additionally, the overexpression of wild-type Rac1 and constitutively active Rac1 increased the size of preexisting spines and the amplitude of mEPSCs in mature neurons (>21 d in vitro) within 24 h after transfection. Together, these results indicate that activation of Rac1 enhances excitatory synaptic transmission by recruiting AMPARs to synapses during spinogenesis, thus providing a mechanistic link between presynaptic and postsynaptic developmental changes. Furthermore, we show that Rac1 has two distinct roles at different stages of neuronal development. The activation of Rac1 initiates spinogenesis at an early stage and regulates the function and morphology of preexisting spines at a later stage.