Corinna Singleman

Fernández, E., Fraboni, M., Valad, J, Avila, S., Edmond, A., & Singleman, C.. in Winter, K. (Ed.) and Bramberger, A. (Ed.) Re-Conceptualizing Safe Space – Supporting Inclusive Education.

2021 in press

Corinna Singleman and Nathalia Holtzman

April 2021

Polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are environmental contaminants known to impact cardiac development, a key step in the embryonic development of most animals. To date, little is understood of the molecular mechanism driving the observed cardiac defects in exposed fishes. The literature shows PCB & TCDD derived cardiac defects are concurrent with, but not caused by, expression of cyp1A, due to activation of the aryl hydrocarbon receptor (AhR) gene activation pathway. However, in this study, detailed visualization of fish hearts exposed to PCBs and TCDD show that, in addition to a failure of cardiac looping in early heart development, the inner endocardial lining of the heart fails to maintain proper cell adhesion and tissue integrity. The resulting gap between the endocardium and myocardium in both zebrafish and Atlantic sturgeon suggested functional faults in endothelial adherens junction formation. Thus, we explored the molecular mechanism triggering cardiac defects using immunohistochemistry to identify the location and phosphorylation state of key regulatory and adhesion molecules. We hypothesized that PCB and TCDD activates AhR, phosphorylating Src, which then phosphorylates the endothelial adherens junction protein, VEcadherin. When phosphorylated, VEcadherin dimers, found in the endocardium and vasculature, separate, reducing tissue integrity. In zebrafish, treatment with PCB and TCDD contaminants leads to higher phosphorylation of VEcadherin in cardiac tissue suggesting that these cells have reduced connectivity. Small molecule inhibition of Src phosphorylation prevents contaminant stimulated phosphorylation of VEcadherin and rescues both cardiac function and gross morphology. Atlantic sturgeon hearts show parallels to contaminant exposed zebrafish cardiac phenotype at the tissue level. These data suggest that the mechanism for PCB and TCDD action in the heart is, in part, distinct from the canonical mechanism described in the literature and that cardiac defects are impacted by this nongenomic mechanism.

https://doi.org/10.1016/j.aquatox.2021.105794

Patrick Johnson, Allan Edmond, Corinna Singleman, Jennifer Valad, Sabrina Avila, and Eva Fernandez

October 2020

Patrick Johnson, Jennifer Valad, Corinna Singleman, Sabrina Avila, and Eva Fernandez

October 2019

https://drive.google.com/drive/u/0/folders/19BV0RPKPDgwr_pqoAgvWquKkJYoql7eh

Corinna Singleman

March 2017

https://academicworks.cuny.edu/gc_etds/2147

Corinna Singleman and Nathalia Holtzman

2016

The Hudson River (HR) is teeming with life, and also with toxins. Over the course of 30 years General Electric released approximately 1.3 million pounds of PCB mixtures (Aroclors) into the HR resulting in lasting contamination. While PCBs are chemically quite stable, they are biologically active causing cancer, reproductive, developmental and survival problems. Fish living and breeding in the HR are exposed to these toxins and suffer the consequences. Sturgeon have historically frequented the HR during spawning seasons and with populations starting to increase, more and more sturgeon return to the river each year to lay their eggs in the contaminated sediments. While some information is available on the consequences of toxin exposure to different fish species, little is understood of sturgeon response to PCBs. Proper heart development is essential to survival of many organisms and PCBs are known to impact cardiac development. This study explored the effects of early toxin exposure on sturgeon heart development using molecular tools to visualize the young sturgeon heart. Shortnose and Atlantic sturgeon hearts exposed to PCB 126, TCDD and an Aroclor mixture showed unique cardiac deformities. PCB 126 caused hearts to not loop properly in early heart development, while TCDD and Aroclor treatments resulted in hearts with chambers that did not balloon. In both situations, the fish likely had problems with blood circulation and in most cases, treated fish died soon after hatching. These toxins have a clear impact on development and survival of sturgeon larvae and may hinder the budding recovery of these endangered species.

Full text: http://www.hudsonriver.org/ls/reports/Polgar_Singleman_TP_05_14_final.pdf

Corinna Singleman and Nathalia Holtzman

July 2014

Zebrafish have been increasingly used as a teaching tool to enhance the learning of many biological concepts from genetics, development and behavior to the understanding of the local watershed. While traditionally, in both research and teaching, zebrafish work has focused on embryonic stages; however later stages, from larval through adulthood, are increasingly being examined. Defining developmental stages based on age is a problematic way to assess maturity because many environmental factors, such as temperature, population density and water quality, impact growth and maturation. Fish length and characterization of key external morphological traits are considered better markers for maturation state. While a number of staging series exist for zebrafish, here we present a simplified normalization table of post-embryonic maturation well suited to both educational and research use. Specifically, we utilize fish size and four easily identified external morphological traits (pigment pattern, tail fin, anal fin and dorsal fin morphology) to describe three larval stages, a juvenile stage, and an adult stage. These simplified maturation standards will be a useful tool for both educational and research protocols.

http://online.liebertpub.com/doi/abs/10.1089/zeb.2014.0976

Corinna Singleman and Nathalia Holtzman

Nov 2012

Background: Cardiac maturation is vital for animal survival and must occur throughout the animal's life. Zebrafish are increasingly used to model cardiac disease; however, little is known about how the cardiovascular system matures. We conducted a systematic analysis of cardiac maturation from larvae through to adulthood and assessed cardiac features influenced by genetic and environmental factors. Results: We identified a novel step in cardiac maturation, termed cardiac rotation, where the larval heart rotates into its final orientation within the thoracic cavity with the atrium placed behind the ventricle. This rotation is followed by linear ventricle growth and an increase in the angle between bulbous arteriosus and the ventricle. The ventricle transitions from a rectangle, to a triangle and ultimately a sphere that is significantly enveloped by the atrium. In addition, trabeculae are similarly patterned in the zebrafish and humans, both with muscular fingerlike projections and muscle bands that span the cardiac chamber. Of interest, partial loss of atrial contraction in myosin heavy chain 6 (myh6/weahu423/+) mutants result in the adult maintaining a larval cardiac form. Conclusions: These findings serve as a foundation for the study of defects in cardiovascular development from both genetic and environmental factors.

http://onlinelibrary.wiley.com/doi/10.1002/dvdy.23882/abstract

Corinna Singleman and Nathalia Holtzman

Sept 2011

In order to analyze heart development over the fish's lifespan, we dissect zebrafish hearts at numerous stages and photograph them for further analysis. This protocol explains two distinct, size dependent dissection techniques for zebrafish, ranging from larvae 3.5 mm standard length (SL) with hearts of 100 μm ventricle length (VL), to adults, with SL of 30 mm and VL 1mm or larger.Larval and adult fish have quite distinct body and organ morphology. Larvae are not only significantly smaller, they have less pigment and each organ is visually very difficult to identify. For this reason, we use distinct dissection techniques. We used pre-dissection fixation procedures, as we discovered that hearts dissected directly after euthanization have a more variable morphology, with very loose and balloon like atria compared with hearts removed following fixation. This protocol will provide a valuable technique for the study of cardiac development maturation and aging.

http://www.jove.com/video/3165/heart-dissection-in-larval-juvenile-and-adult-zebrafish-danio-rerio?id=3165