Fibronectin and integrin alpha 5 play essential roles in the development of the cardiac neural crest

Abstract

Cardiac neural crest (CNC) plays a requisite role during cardiovascular development and defects in the formation of CNC-derived structures underlie several common forms of human congenital birth defects. Migration of the CNC cells to their destinations as well as expansion and maintenance of these cells are important for the normal development of the cardiac outflow tract and aortic arch arteries; however, molecular mechanisms regulating these processes are not well-understood. Fibronectin (FN) protein is present along neural crest migration paths and neural crest cells migrate when plated on FN in vitro; therefore, we tested the role of FN during the development of the CNC in vivo. Our analysis of the fate of the neural crest shows that CNC cells reach their destinations in the branchial arches and the cardiac outflow tract in the absence of FN or its cellular receptor integrin α5β1. However, we found that FN and integrin α5 modulate CNC proliferation and survival, and are required for the presence of normal numbers of CNC cells at their destinations.

Neural crest cell-autonomous roles of fibronectin in cardiovascular development

“…In such mutants the originally well-formed 4th pair of PAAs regressed because of either (a) insufficiency in cardiac NC cell population or (b) defective differentiation of the cardiac NC into VSMCs (Conway et al, 2003;Stoller and Epstein, 2005). Consistent with our previous studies showing that Fn1 was not required for NC migration in global Fn1-null mutants (Mittal et al, 2010), the deletion of Fn1 in NC cells did not impair NC migration (compare Fig. S3A-B″ with C-D″).…”

“…Fn1 mRNA becomes detectable in the cardiac NC at about the 8th-10th somite stage of mouse development, and its expression is maintained in the dorsal neural tube at least until the 23rd somite stage (Mittal et al, 2010). Studies using Fn1 flox/flox mice, a strain generated 14 years ago, show that the Fn1 protein is downregulated within 24 h of Cre expression (Sakai et al, 2001).…”

“…In these strains, Cre expression in the cardiac NC is already evident by the 5th-somite stage, which is ∼6 h prior to the onset of Fn1 mRNA expression in that region (Mittal et al, 2010;Stottmann and Klingensmith, 2011 (Muzumdar et al, 2007;Soriano, 1999). The inclusion of reporters allowed the identification and tracking of NC descendants in control and mutant embryos.…”

“…On their way to pharyngeal arches, NC cells migrate through the cranial mesoderm that expresses Fn1 (Mittal et al, 2010;Peters and Hynes, 1996). NC cells directly adjacent to the PAA endothelium within the pharyngeal arches are exposed to endothelial Fn1 ( Taken together, these data suggest that NC-derived Fn1 mediates differentiation of NC cells into VSMCs in NC cell-autonomous manner.…”

“…In our prior work, we made the unexpected observation that fibronectin 1 (Fn1) mRNA and protein are highly enriched in distinct regions of the mouse embryo, including regions corresponding to the developing NC and the pharyngeal arches 3, 4 and 6 (Mittal et al, 2010). Interestingly, many other ECM glycoproteins are also non-uniformly distributed during embryogenesis (reviewed in Astrof, 2013;Watt and Huck, 2013).…”