Abstract

Neural tube defects (NTDs) are a common congenital disorder resulting from failed neural tube formation, the precursor of the brain and spinal cord. The complex etiology of NTDs involve both genetic and environmental factors, thus investigating gene-environment interactions is critical to understanding how NTDs occur or how NTDs may be prevented. For example, iron deficiency is among the most prevalent micronutrient deficiencies in pregnancy and there is evidence that iron deficiency can increase the risk of NTDs. Folic acid (FA) fortification in grain was implemented in the US in 1998 and now in many countries for the purpose of prevention of neural tube defects (NTDs). In 2017, the US Preventive Services Task Force further recommended the consumption of FA-containing multivitamin/minerals (MVM) for women of childbearing age. Despite the great benefit of FA on NTD prevention, NTDs remain a serious risk. Our studies focus on mouse models of NTDs and I will discuss two projects. First, the benefits of MVM supplementation are emphasized, but a comparison between MVM supplementation and FA alone on neural tube closure and organ development has not been evaluated, particularly in the context of genetic mutations that lead to NTDs. Using a set of NTD models we have compared MMV to FA supplementation. MVM supplementation shows better improvement than FA alone in the penetrance of spinal and cranial NTDs. We are also using human iPSCs to generate organoids that assume a shape similar to the human spinal neural tube, and display neural tube characteristics, for example apical constriction and interkinetic nuclear migration. Subjecting the organoids to various molecular perturbations, such as Rho-kinase inhibitor-induced defects in apical constriction, we have found that both MVM and FA largely prevents this molecular deficit. The goal is to use the mouse NTD model and organoid system to better understand how FA/MVM act to prevent NTDs. Second, we are striving to move beyond the relatively non-specific recommendations of FA/MVM supplementation to more personalized therapies that take into account the molecular underpinning of the NTD. For example, Iron homeostasis is not only controlled by the concentration of iron in diet, but by proteins responsible for its cellular uptake and metabolism. Sorting nexin 3 (Snx3) is known to regulate recycling of the transferrin receptor (TFRC), a mechanism necessary for cellular uptake of iron, and when Snx3 is knocked out in mice, embryos develop cranial NTDs. We hypothesize that in Snx3 mutants, mistrafficking of TFRC results in disrupted iron homeostasis which contributes to the failure of NT closure. Our current studies are evaluating whether intracellular iron levels are altered in Snx3 mutants and whether maternal diets supplemented with iron can prevent NTDs in the Snx3 background. The hope is that by taking into account the biological process that is disrupted, more tailored therapies can be envisioned to better prevent NTDs.

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