High‐affinity folate receptor in cardiac neural crest migration: A gene knockdown model using siRNA

Abstract

Folate supplementation reduces the incidence of congenital heart defects, but the nature of this protective mechanism remains unclear. Immunolabeling demonstrated that the neural tube and neural crest (NC) cells were rich in the high-affinity folate receptor FOLR1and during the early stages of development FOLR1 was found principally in these cells. Suppression of Folr1 expression in the nascent cardiac NC by site-directed short-interfering RNA (siRNA) altered cardiac NC cell mitosis and subsequent migration patterns leading to abnormal development of the pharyngeal arch arteries (PAA) and outflow tract. qPCR analysis demonstrated that the siRNA treatment significantly reduced Folr1 24 hr after treatment. These treatments also significantly reduced mitosis in the neural tube, but adjacent, nontreated areas were unaffected. In summary, a brief reduction in the expression of Folr1 during a critical stage of NC development had long-term consequences for the development of the PAA and outflow tract. Developmental Dynamics 239:1136-1144,

Folate, Homocysteine and the Cardiac Neural Crest

“…But more controlled animal experimentation has demonstrated quite clearly that insufficient maternal folate for only 48 hr can produce major structural defects in mammalian embryos including both NTD and CHD (Nelson et al, ; Baird et al, ). Blocking neural crest cell folate reception for only 24 hr produces abnormal heart development in avian embryos (Rosenquist et al, ). The key question is, why does insufficient folate have such an exceptional, specific, and rapid effect upon the neural tube and neural crest?…”

“…Developmental biologists typically are well aware of the potential of their work to have some impact upon human health, and are able to describe it in that context. A summary of the clinical importance of congenital heart defects (CHD) is a common introduction in reports of various kinds of experiments that utilize animal models to study heart development (e.g., Conway et al, ; Kirby and Sahn, ; Linask and Huhta, ; Rosenquist et al, ) or human population‐based studies of congenital heart defects (e.g., Botto et al, ; Hoffman and Kaplan, ; Pierpont et al, ; Hobbs et al, ; van der Linde et al, ). These data provide an excellent rationale for either animal model or population‐based studies, and may be summarized briefly as follows: CHD is the most common congenital defect worldwide, effecting 1–10% of live births (this variability results from different study populations, differing criteria for inclusion of different types of CHD in the data analysis, variations in the sensitivity of the tools used to detect CHD, and other factors). CHD is the most common cause of infant mortality in the United States and Europe. The cumulative cost of CHD in dollars or euros is in the hundreds of millions annually. It is assumed that a large proportion of stillbirths are the result of CHD, so the actual number of CHD would be much higher. …”

“…In fact, the overall rate of CHD has been increasing, apparently because of more sensitive diagnoses (Berrey and Helman, ; Lambert et al, ; van der Linde et al, ). It is common for authors of both experimental and population‐based studies to assert that progress has been hampered by the fact that the origins of most CHD are, if not completely unknown, at least difficult to pinpoint because of the complexity of gene–environment interactions that contribute to their etiology (e.g., Shaw et al, ; Finnell et al, , ; van Beynum et al, ; Goldmuntz et al, ; Zhu et al, ; Rosenquist et al, ), a complexity that applies to the general topic of congenital defects, not just to CHD (Brent, ).…”

Xenopus Reduced Folate Carrier Regulates Neural Crest Development Epigenetically

“…The migration of cardiac neural crest cells are affected in the Folr1 mutant embryos [38]. In chick embryos, interference with Folr1 expression also reduced the formation and migration of cardiac neural crest cells [39]. We showed here in Xenopus embryos that inhibition of RFC blocked the expression of a series of neural crest marker genes including Zic1 , Snail1 , Snail2 , FoxD3 and Twist1 , but had no clear effects on Pax3 and Msx1 (Fig.…”

Novel functions of folate receptor alpha in CNS development and diseases

“…Additionally, the nullizygotes also exhibit craniofacial abnormalities, such as cleft lip and palate, suggesting that FRα affects neural crest cell migration. This hypothesis was later confirmed by a brief and critical interruption of FRα expression by siRNA during embryo development which caused a failure of neural crest cell migration into pharyngeal arches resulting in abnormal development of pharyngeal arch artery and heart [43].…”