# Mechanisms regulating the formation of the pharyngeal arch arteries

> **NIH NIH R01** · RBHS-NEW JERSEY MEDICAL SCHOOL · 2020 · $397,500

## Abstract

PROJECT SUMMARY
Formation of the pharyngeal arch arteries (PAAs) is defective in patients with DiGeorge syndrome, the most
common chromosomal abnormality in humans. However, the cellular and molecular mechanisms regulating
PAA formation are not well understood. For many years, it was believed that PAAs developed by the process
of angiogenesis, whereby PAAs were thought to form as branches stemming from the dorsal aorta that invade
the avascular pharyngeal arches. However, recent studies in mutant mice with defective PAA formation
suggested that the mutant phenotypes and the presence of a primitive vascular plexus within the pharyngeal
arches were incompatible with the idea that PAAs formed via angiogenesis. Instead, these studies suggested
that PAAs develop by the process of vasculogenesis, whereby PAAs arise de-novo from pharyngeal vascular
endothelial progenitors. We employed transient labeling and cell lineage tracking to resolve this issue and
demonstrated that endothelial cells of PAAs arise from the second heart field. Furthermore, our time-resolved,
3D confocal imaging showed that PAAs form by reorganization of the primitive vascular plexus into the PAA. In
the course of our studies, we discovered that the extracellular matrix glycoprotein fibronectin (Fn1) is required
for the formation of the 4th pair of PAAs, and that conditional deletion of Fn1 in the Isl1 lineage caused severe
congenital aortic arch defects, similar to those observed in DiGeorge syndrome. We found that the number and
density of endothelial cells in Fn1flox/-;Isl1Cre animals is much lower than in controls, and hypothesize that Fn1
mediates PAA formation by regulating the differentiation of SHF-derived endothelial progenitors into
endothelial cells or by regulating the migration of endothelial progenitors from the SHF into the pharyngeal
arches. In this grant application, we propose to test these hypotheses and to refine the spatio-temporal
mechanisms regulating the development of PAA progenitors. We then propose to apply our methodology to
systematically elucidate the basis for the PAA formation defects in Tbx1+/- mutants that model the DiGeorge
syndrome. We plan to achieve these goals by addressing the following specific aims: 1) To determine the
mechanisms, by which Fn1 regulates PAA morphogenesis; 2) To determine the role of VEGFR2positive cells
within the SHF in PAA development; and 3) To determine the stage(s) of PAA formation regulated by Tbx1.
We will use conditional mutagenesis, time-resolved confocal imaging and 3D reconstruction to test our
hypotheses, and investigate the role of Fn1 in growth factor signaling during PAA formation. Furthermore, we
will employ an innovative live multi-photon microscopy to investigate the dynamics of endothelial cells during
PAA formation in living embryos, and the roles of Fn1 and Tbx1 in this process. Completion of these studies
will provide important insights into the mechanisms of normal PAA formation and into alterations th...

## Key facts

- **NIH application ID:** 9702895
- **Project number:** 5R01HL134935-04
- **Recipient organization:** RBHS-NEW JERSEY MEDICAL SCHOOL
- **Principal Investigator:** Sophie Astrof
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $397,500
- **Award type:** 5
- **Project period:** 2017-08-05 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9702895

## Citation

> US National Institutes of Health, RePORTER application 9702895, Mechanisms regulating the formation of the pharyngeal arch arteries (5R01HL134935-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9702895. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*