Background Prenatal alcohol exposure (PAE) is associated with an increased incidence of congenital heart defects (CHD), in particular outflow tract (OFT) defects. However, the variability in the incidence of CHD following PAE has not been fully explored. We hypothesize that a concomitant, relevant genetic defect would potentiate the adverse effect of PAE and partially explain the variability of PAE‐induced CHD incidence. Methods The OFT is formed by the second heart field (SHF). Our PAE model consisted of two intraperitoneal injections (3 g/kg, separated by 6 hr) of 30% ethanol on E6.5 during SHF specification. The impact of genetic defects was studied by SHF‐specific loss of Delta‐like ligand 4 (Dll4), fibroblast growth factor 8 (Fgf8) and Islet1. Results Acute PAE alone significantly increased CHD incidence (4% vs. 26%, p = .015) with a particular increase in OFT alignment defects, viz., double outlet right ventricle (0 vs. 9%, p = .02). In embryos with a SHF genetic defect, acute PAE significantly increased CHD incidence (14 vs. 63%, p < .001), including double outlet right ventricle (6 vs. 50%, p < .001) compared to controls. PAE (p = .01) and heterozygous loss of Dll4 (p = .04) were found to independently contribute to CHD incidence, while neither Islet1 nor Fgf8 defects were found to be significant. Conclusions Our model recapitulates the increased incidence of OFT alignment defects seen in the clinic due to PAE. The presence of a concomitant SHF genetic mutation increases the incidence of PAE‐related OFT defects. An apparent synergistic interaction between PAE and the loss of DLL4‐mediated Notch signaling in OFT alignment requires further analysis.
Introduction: Wnt5a is a known regulator of planar cell polarity (PCP) signaling in second heart field (SHF) progenitor cells. It is generally believed that Wnt5a ligands are secreted by the SHF; however, SHF-specific conditional deletion of Wnt5a does not recapitulate outflow tract (OFT) defects observed in global Wnt5a mutants. Hypothesis: Given the proximity and interaction between neural crest cells (NCC) and cranial SHF that contributes to the developing OFT, we hypothesize that NCC may serve as an additional source of Wnt5a for SHF progenitors. Methods: Wnt5a was conditionally deleted in the neural crest using transgenic Wnt1-cre mice. Embryos were harvested from control and mutant litter mates and immunofluoresence, in situ hybridization, and hematoxylin-eosin stains were performed on histologic sections using standard techniques. India ink injections were performed to evaluate pharyngeal arch artery and outflow tract morphology in whole mount embryos. Results: Wnt1-cre driven conditional deletion of Wnt5a in NCC did not impact NCC survival or migration into the developing OFT. However, SHF cells in mutant E10.5 embryos showed altered PCP signaling with reduced phalloidin and laminin expression. The resulting loss in polarized directional movement of the SHF led to reduced incorporation into and elongation of the developing OFT. The shortened OFT was mal-aligned resulting in fully penetrant double outlet right ventricle (DORV) at E14.5. In addition, maturation of pharyngeal arch arteries was also impaired such that all mutants express pharyngeal arch artery defects, including aortic arch abnormalities and aberrant right subclavian artery. In contrast, there was no observed effect on PCP in the more caudal SHF cells, and none of the mutant embryos had inflow tract or venous pole defects. Conclusions: Our results demonstrate that NCC are a novel source of Wnt5a. NCC-derived Wnt5a is critically required to regulate PCP signals in the most cranial SHF regulating the development of the OFT and pharyngeal arch arteries.
Background The pathogenesis of congenital heart disease (CHD) remains largely unknown, with only a small percentage explained solely by genetic causes. Modifiable environmental risk factors, such as alcohol, are suggested to play an important role in CHD pathogenesis. We sought to evaluate the association between prenatal alcohol exposure and CHD to gain insight into which components of cardiac development may be most vulnerable to the teratogenic effects of alcohol. Methods and Results This was a retrospective analysis of hospital discharge records from the California Office of Statewide Health Planning and Development and linked birth certificate records restricted to singleton, live‐born infants from 2005 to 2017. Of the 5 820 961 births included, 16 953 had an alcohol‐related International Classification of Diseases , Ninth and Tenth Revisions (ICD‐9; ICD‐10 ) code during pregnancy. Log linear regression was used to calculate risk ratios (RR) for CHD among individuals with an alcohol‐related ICD ‐9 and ICD10 code during pregnancy versus those without. Three models were created: (1) unadjusted, (2) adjusted for maternal demographic factors, and (3) adjusted for maternal demographic factors and comorbidities. Maternal alcohol‐related code was associated with an increased risk for CHD in all models (RR, 1.33 to 1.84); conotruncal (RR, 1.62 to 2.11) and endocardial cushion (RR, 2.71 to 3.59) defects were individually associated with elevated risk in all models. Conclusions Alcohol‐related diagnostic codes in pregnancy were associated with an increased risk of an offspring with a CHD, with a particular risk for endocardial cushion and conotruncal defects. The mechanistic basis for this phenotypic enrichment requires further investigation.
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