Browsing by Subject "Neural tube defects"
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Item Autoimmune processes in the placentas of neural tube defect-affected pregnancies(2013-05) Palacios, Ana Maria; Finnell, Richard H.Neural Tube Defects (NTDs) are a group of common congenital malformations that result from incomplete neural tube closure leading to abnormalities of the brain and/or spinal cord. Unfortunately, their etiology remains unknown, probably due to complex multifactorial interactions. The protective effect of dietary folates in preventing NTDs is well known, but this beneficial effect is limited to the 60 to 70% of cases; leaving 30% of the population without any known option for improving pregnancy outcomes. The mechanism by which folates rescue NTD-affected embryos is poorly understood, but the ability of folate supplementation to overcome a significant percentage of NTDs and the critical role of 5-methyltetrahydrofolate in the remethylation of homocysteine (Hcy) to methionine in the placenta suggests that folate binding and/or transport might play a critical role during development. We hypothesized that maternal autoantibodies (AB) targeting placental folate receptor alpha (FRα) are blocking the receptor and limiting the ability of the FRα to bind folates, reducing intraembryonic folate levels. Furthermore, we hypothesized that AB binding to other relevant proteins required for trophoblastic growth and placentation can be involved in activating pathologic inflammatory pathways that can result in suboptimal uptake of nutrients and contribute to an abnormal closure of the neural tube. We developed a high throughput ELISA to evaluate whether mothers experiencing pregnancies complicated with NTDs are more likely to have placental AB to FRα than are mothers experiencing normal pregnancies. We optimized and simplified a protocol for AB elution from placental tissues and determined whether these antibodies were blocking the FRα from binding with available folates. Although anti-FRα IgG antibodies were not associated to the blocking activity in this study, we found that the blocking activity was higher in the placentas from NTD-affected pregnancies compared to controls, that FRα IgM antibodies are most likely the type of antibody produced during gestation that is most relevant to the blocking activity and that it is unlikely that autoimmunity against other developmental proteins associated with NTDs is generating the NTDs.Item Dietary and genetic influences on neural tube defects(2014-08) Fathe, Kristin Renee; Finnell, Richard H.Neural tube defects (NTDs) are a world health issue, affecting approximately 1 in every 1000 live births. These congenital defects arise from the improper closure of the neural tube during development, resulting in significant, life-threatening malformations of the central nervous system. Although it has been observed that supplementing women of child-bearing age with folates greatly decreases the chances of having an NTD affected baby, unfortunately these defects still occur. It is accepted that these complex disorders arise from a combination of genetic, environmental, and dietary influences. One such dietary influence is the one-carbon metabolism metabolite, homocysteine. Homocysteine is a byproduct of methylation reactions in the cell that exists in an inverse homeostasis with folate. Homocysteine can also undergo a transformation that allows it to then react with exposed lysine or cysteine residues on proteins, in a process known as N-homocysteinylation or S-homocysteinylation respectively. High levels of homocysteine have been long correlated with many disease states, including NTDs. One potential mechanism by which homocysteine confers its negative effects is through protein N-homocysteinylation. Here, a novel and high-throughput assay for N-homocysteinylation determination is described. This assay is shown to be accurate with mass spectrometry then shown to be biologically relevant using known hyperhomocysteinemia mouse models. This assay was then applied to a cohort of neural tube closure staged mouse embryos with two different genetic mutations that have previously been shown to predispose mice to NTDs. The genotypes explored here are mutations to the LRP6 gene and the Folr1 gene, both of which have been described as folate-responsive NTD mouse models. It was seen that maternal diet and embryonic genotype had the largest influence on the developmental outcome of these embryos; however, the inverse relationship between folate and homocysteine seemed to be established at this early time point, emphasizing the importance of the balance in one-carbon metabolism. One of these genes, LRP6, was then explored in a human cohort of spina bifida cases. Four novel mutations to the LRP6 gene were found and compared to the mouse model used in the previous study. One of the mutations found in the human population was seen to mimic that of the LRP6 mouse model, therefore expanding the potential of this NTD model.