# Nr2f1a suppresses bulbous arteriosus identity in the zebrafish atrium

> **NIH NIH F31** · CINCINNATI CHILDRENS HOSP MED CTR · 2020 · $40,686

## Abstract

Project Summary/Abstract
Normal vertebrate heart development involves the preservation of proper cardiac chamber proportions. Improper
maintenance of cardiomyocyte (CM) identity underlies numerous congenital heart defects (CHDs), which can
lead to cardiomyopathy and morbity in newborns as well as throughout adulthood. Nr2f orphan nuclear hormone
receptors are conserved regulators of atrial development in vertebrates. NR2F2 mutations are associated with
CHDs in humans. Our recent work demonstrates that zebrafish Nr2f1ais the functional equivalent of mammalian
Nr2f2 with respect to early chamber development, as it is specifically expressed in the atrium and is vital for
proper atrial differentiation. Here, we use a novel ENU-induced mutant named acorn worm (aco), which exhibits
a loss of Nr2f1a expression. While engineered nr2f1a mutant embryos are early lethal in our hands, we have
found that some aco mutants are viable to adulthood, affording a unique opportunity to investigate the effects of
prolonged Nr2f1a loss in the mature heart. Adult aco hearts develop a non-contractile atrial chamber, which is
surrounded by opaque connective tissue. Surprisingly, in contrast to the prediction from mouse conditional Nr2f2
KOs that atrial CMs lacking Nr2f2 would take on ventricular CM identity, histological analysis using AFOG
staining revealed the adult aco atria lack pectinate or trabecular structures and instead have collagenous matrix
similar to the bulbous arteriosus (BA) of the outflow tract. Transcriptome analyses from isolated aco cardiac
chambers and in situ hybridization affirmed that aco mutant atria express BA-specific genes while upregulating
retinoic acid (RA) signaling components. We find the BA-like identity of the atrium is first observed at the venous
pole starting at 3 weeks post fertilization (wpf). In Aim 1, we will use a sophisticated genetic lineage tracing
system to permanently label atrial CMs and elucidate the origin of the BA-like atrial chamber in aco mutant adults.
In Aim 2, we will use novel transgenic tools to restore nr2f1a specifically in atrial CMs beginning at 2 wpf to
determine the developmental window when Nr2f1a is critical to suppress the BA-like atria. In Aim 3, we will use
pharmacological methods to modulate retinoic acid signaling (RA) signaling levels from 2 to 3 wpf to elucidate
excess RA signaling downstream of Nr2f1a in aco mutants promotes the formation of the BA-like atrial chamber.
Therefore, our findings highlight an unexpected role for Nr2f1a in repressing BA-identity within atria, which may
yield novel insight into the molecular and cellular etiology of CHDs found in children and adults.

## Key facts

- **NIH application ID:** 9921208
- **Project number:** 5F31HL147399-02
- **Recipient organization:** CINCINNATI CHILDRENS HOSP MED CTR
- **Principal Investigator:** Jacob Gafranek
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $40,686
- **Award type:** 5
- **Project period:** 2019-04-11 → 2022-04-10

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9921208

## Citation

> US National Institutes of Health, RePORTER application 9921208, Nr2f1a suppresses bulbous arteriosus identity in the zebrafish atrium (5F31HL147399-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9921208. Licensed CC0.

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