Thymidylate synthase polymorphisms and risk of conotruncal heart defects.

In this study, we investigated whether the two TYMS functional variants (28 bp VNTR and 1494del6) (275 cases and 653 controls) and six selected SNPs (265 case infants, 535 control infants; 169 case mothers and 276 control mothers) were associated with risks of conotruncal heart defects. Further, we evaluated interaction effects between these gene variants and maternal folate intake for risk of CTD. Cases with diagnosis of single gene disorders or chromosomal aneusomies were excluded. Controls were randomly selected from area hospitals in proportion to their contribution to the total population of live-born infants. DNA samples were collected using buccal brushes or drawn from the repository of newborn screening blood specimens when available. Genetic variants were treated as categorical variables (homozygous referent, heterozygote, homozygous variant). Odds ratios and 95% confidence intervals (CI) were computed to estimate risks among all subjects, Hispanic and non-Hispanic whites, respectively, using logistic regression. Gene-folate interactions were assessed for these variants by adding an interaction term to the logistic model. A dichotomized composite variable, "combined folate intake," was created by combining maternal peri-conceptional use of folic acid-containing vitamin supplements with daily dietary intake of folate. In general, the results do not show strong gene-only effects on risk of CTD. We did, however, observe a 3.6-fold increase in CTD risk (95% CI: 1.1-11.9) among infants who were homozygotes for the 6 bp deletion in the 3'-untranslated region (UTR) (1694del6) and whose mothers had low folate intake during the peri-conceptional period.

Methylenetetrahydrofolate reductase deficiency and low dietary folate increase embryonic delay and placental abnormalities in mice.

BACKGROUND: Despite extensive research on mild methylenetetrahydrofolate reductase (MTHFR) deficiency and low dietary folate in different disorders, the association of these metabolic disturbances with a variety of congenital defects and pregnancy complications remains controversial. In this study we investigated the effects of MTHFR and dietary folate deficiency at 10.5 days post coitum (dpc) in our mouse model of mild MTHFR deficiency. METHODS: Mthfr +/+ and +/- female mice were fed a control or folic acid-deficient diet for 6 weeks, then mated with Mthfr +/- males. At 10.5 dpc, embryos were examined and placentae were collected for histologic evaluation. RESULTS: Maternal MTHFR and folate deficiencies resulted in increased developmental delays and smaller embryos. We also observed a low frequency of a variety of embryonic defects in the experimental groups, such as neural tube, heart looping, and turning defects; these results mimic the low incidence and multifactorial nature of these anomalies in humans. Folate-deficient mice also had increased embryonic losses and severe placental defects, including placental abruption and disturbed patterning of placental layers. Folate-deficient placentae had decreased ApoA-I expression, and there was a trend toward a negative correlation between ApoA-I expression with maternal homocysteine concentrations. CONCLUSIONS: Our study provides biological evidence linking maternal MTHFR and dietary folate deficiencies to adverse pregnancy outcomes in mice. It underscores the importance of folate not only in reducing the incidence of early embryonic defects, but also in the prevention of developmental delays and placental abnormalities that may increase susceptibility to other defects and to reproductive complications.

Mitogen-activated protein kinases in heart development and diseases.

Mitogen-activated protein (MAP) kinases belong to a highly conserved family of Ser-Thr protein kinases in the human kinome and have diverse roles in broad physiological functions. The 4 best-characterized MAP kinase pathways, ERK1/2, JNK, p38, and ERK5, have been implicated in different aspects of cardiac regulation, from development to pathological remodeling. Recent advancements in the development of kinase-specific inhibitors and genetically engineered animal models have revealed significant new insights about MAP kinase pathways in the heart. However, this explosive body of new information also has yielded many controversies about the functional role of specific MAP kinases as either detrimental promoters or critical protectors of the heart during cardiac pathological processes. These uncertainties have raised questions on whether/how MAP kinases can be targeted to develop effective therapies against heart diseases. In this review, recent studies examining the role of MAP kinase subfamilies in cardiac development, hypertrophy, and survival are summarized.

Cardiofaciocutaneous (CFC) syndrome associated with muscular coenzyme Q10 deficiency.

The cardiofaciocutaneous (CFC) syndrome is characterized by congenital heart defect, developmental delay, peculiar facial appearance with bitemporal constriction, prominent forehead, downslanting palpebral fissures, curly sparse hair and abnormalities of the skin. CFC syndrome phenotypically overlaps with Noonan and Costello syndromes. Mutations of several genes (PTPN11, HRAS, KRAS, BRAF, MEK1 and MEK2), involved in the mitogen-activated protein kinase (MAPK) pathway, have been identified in CFC-Costello-Noonan patients. Coenzyme Q10 (CoQ10), a lipophilic molecule present in all cell membranes, functions as an electron carrier in the mitochondrial respiratory chain, where it transports electrons from complexes I and II to complex III. CoQ10 deficiency is a rare treatable mitochondrial disorder with various neurological (cerebellar ataxia, myopathy, epilepsy, mental retardation) and extraneurological (cardiomyopathy, nephropathy) signs that are responsive to CoQ10 supplementation. We report the case of a 4-year-old girl who presented a CFC syndrome, confirmed by the presence of a pathogenic R257Q BRAF gene mutation, together with a muscular CoQ10 deficiency. Her psychomotor development was severely impaired, hindered by muscular hypotonia and ataxia, both improving remarkably after CoQ10 treatment. This case suggests that there is a functional connection between the MAPK pathway and the mitochondria. This could be through the phosphorylation of a nuclear receptor essential for CoQ10 biosynthesis. Another hypothesis is that K-Ras, one of the proteins composing the MAPK pathway, might be recruited into the mitochondria to promote apoptosis. This case highlights that CoQ10 might contribute to the pathogenesis of CFC syndrome.

Na,K-ATPase is essential for embryonic heart development in the zebrafish.

Na,K-ATPase is an essential gene maintaining electrochemical gradients across the plasma membrane. Although previous studies have intensively focused on the role of Na,K-ATPase in regulating cardiac function in the adults, little is known about the requirement for Na,K-ATPase during embryonic heart development. Here, we report the identification of a zebrafish mutant, heart and mind, which exhibits multiple cardiac defects, including the primitive heart tube extension abnormality, aberrant cardiomyocyte differentiation, and reduced heart rate and contractility. Molecular cloning reveals that the heart and mind lesion resides in the alpha1B1 isoform of Na,K-ATPase. Blocking Na,K-ATPase alpha1B1 activity by pharmacological means or by morpholino antisense oligonucleotides phenocopies the patterning and functional defects of heart and mind mutant hearts, suggesting crucial roles for Na,K-ATPase alpha1B1 in embryonic zebrafish hearts. In addition to alpha1B1, the Na,K-ATPase alpha2 isoform is required for embryonic cardiac patterning. Although the alpha1B1 and alpha2 isoforms share high degrees of similarities in their coding sequences, they have distinct roles in patterning zebrafish hearts. The phenotypes of heart and mind mutants can be rescued by supplementing alpha1B1, but not alpha2, mRNA to the mutant embryos, demonstrating that alpha1B1 and alpha2 are not functionally equivalent. Furthermore, instead of interfering with primitive heart tube formation or cardiac chamber differentiation, blocking the translation of Na,K-ATPase alpha2 isoform leads to cardiac laterality defects.

Antioxidant status in newborns and infants suffering from congenital heart defects.

There is a common view that free radicals may play an important role in tissue damage resulting from circulatory insufficiency, cardiosurgery etc. There are very few data concerning the involvement of free radical reactions in the newborns and infants suffering from congenital heart defects (CHD). Antioxidant status was evaluated in 41 newborns and infants under 1 year of age, among them 23 suffering from CHD (14 with left-to-right shunt and 9 with cyanotic heart defect) and 18 healthy controls. The study based on the assessment of activities of antioxidant enzymes in blood (superoxide dismutase, catalase and glutathione peroxidase), levels of low molecular weight antioxidants (vitamin E, uric acid and selenium) and the concentration of malondialdehyde (MDA) as a marker of lipid peroxidation. All subjects had low blood selenium concentration as compared to the level considered as being adequate. Infants suffering from CHD had lower, as compared to healthy controls, plasma vitamin E concentration. The difference was significant in the case of acyanotic ones. The activities of superoxide dismutase and catalase in infants with CHD were not significantly different from the respective values recorded in healthy controls. The activity of glutathione peroxidase in whole blood was the lowest in infants with cyanotic heart defect in whom lipid peroxidation, as evaluated by MDA level, was the most enhanced. Significantly higher plasma concentration of uric acid which may be interpreted as a positive mechanism enabling better protection of red blood cells from peroxidative damage was found in this group of infants. It is concluded that enhanced oxidative stress due to imbalance between prooxidant and antioxidant reactions appears to be associated with congenital heart defect pathology in infants.