Mis-Expression of a Cranial Neural Crest Cell-Specific Gene Program in Cardiac Neural Crest Cells Modulates HAND Factor Expression, Causing Cardiac Outflow Tract Phenotypes.

Joshua W Vincentz,David E Clouthier,Anthony B Firulli

doi:10.3390/jcdd7020013

Abstract

Congenital heart defects (CHDs) occur with such a frequency that they constitute a significant cause of morbidity and mortality in both children and adults. A significant portion of CHDs can be attributed to aberrant development of the cardiac outflow tract (OFT), and of one of its cellular progenitors known as the cardiac neural crest cells (NCCs). The gene regulatory networks that identify cardiac NCCs as a distinct NCC population are not completely understood. Heart and neural crest derivatives (HAND) bHLH transcription factors play essential roles in NCC morphogenesis. The Hand1PA/OFT enhancer is dependent upon bone morphogenic protein (BMP) signaling in both cranial and cardiac NCCs. The Hand1PA/OFT enhancer is directly repressed by the endothelin-induced transcription factors DLX5 and DLX6 in cranial but not cardiac NCCs. This transcriptional distinction offers the unique opportunity to interrogate NCC specification, and to understand why, despite similarities, cranial NCC fate determination is so diverse. We generated a conditionally active transgene that can ectopically express DLX5 within the developing mouse embryo in a Cre-recombinase-dependent manner. Ectopic DLX5 expression represses cranial NCC Hand1PA/OFT-lacZ reporter expression more effectively than cardiac NCC reporter expression. Ectopic DLX5 expression induces broad domains of NCC cell death within the cranial pharyngeal arches, but minimal cell death in cardiac NCC populations. This study shows that transcription control of NCC gene regulatory programs is influenced by their initial specification at the dorsal neural tube.

Highlights

Congenital heart defects (CHDs) afflict roughly 1% of newborns and affect the quality of life of more than 1 million adults in the United States [1]
The mandible is hypoplastic and misshaped (Figure 1D, E). This phenotype is similar to what is observed in HAND1 dimer mutant mice [9] but is far more severe than observed in embryos recently reported in which a Dlx5 cDNA was inserted into the ROSA26 locus and activated in neural crest cells (NCCs) (NCCDlx5) [23]
To determine whether gene expression is altered in the Dlx5 NCC oe NCCs that contribute to the outflow tract (OFT), we looked at the expression of the cardiac NCC and OFT myocardium marker Hand2 [28,29] and the NCC marker Sox9 [30,31] (Figure 6)

Summary

Introduction

Congenital heart defects (CHDs) afflict roughly 1% of newborns and affect the quality of life of more than 1 million adults in the United States [1]. Many CHDs affect the cardiac outflow tract (OFT) [2]. A significant portion of CHDs can, be attributed to developmental dysfunction of one of the main developmental progenitors of the OFT, known as the neural crest cells (NCCs). NCCs migrate from the dorsal neural tube throughout the developing embryo [2]. Different NCC subpopulations differentiate into distinct tissue types. The cardiac NCCs differentiate into smooth muscle and connective tissue to form portions of the aorta, pulmonary artery, and nascent ventricular septum. NCC have been well studied, the gene regulatory networks that drive NCCs cells to delaminate from the neural tube, migrate to their destinations, and differentiate into their specified cell type identity are still not completely understood

Methods

Results

Conclusion