Association between maternal single nucleotide polymorphisms in genes regulating glucose metabolism and risk for neural tube defects in offspring

Parental genetic effects on the offspring's phenotype without transmission of the gene itself-pathophysiology and clinical evidence

Parental genes can influence the phenotype of their offspring through genomic-epigenomic interactions even without the direct inheritance of specific parental genotypes. Maternal genetic variations can affect the ovarian and intrauterine environments and potentially alter lactation behaviors, impacting offspring nutrition and health outcomes independently of the fetal genome. Similarly, paternal genetic changes can affect the endocrine system and vascular functions in the testes, influencing sperm quality and seminal fluid composition. These changes can initiate early epigenetic modifications in sperm, including alterations in microRNAs, tRNA-derived small RNAs (tsRNAs), and DNA methylation patterns. These epigenetic modifications might induce further changes in target organs of the offspring, leading to modified gene expression and phenotypic outcomes without transmitting the original parental genetic alterations. This review presents clinical evidence supporting this hypothesis and discusses the potential underlying molecular mechanisms. Parental gene-offspring epigenome-offspring phenotype interactions have been observed in neurocognitive disorders and cardio-renal diseases.

MTHFR C677T and MTR A2756G Gene Polymorphism in Neural Tube Defect Patients and Its Association with Red Blood Cell Folate Level in Eastern Indian Population

Introduction

Single-nucleotide polymorphism (SNP) is a single-nucleotide change in a deoxyribose nucleic acid (DNA) sequence that occurs in >1% of population. Methylene tetra hydro folate reductase (MTHFR) C677T (rs1801133) and methionine synthase enzyme (MTR) A2756G (rs1805087) are two such SNPs occurring in coding sequence of the respective genes, which are frequently seen with neural tube defects (NTDs). MTHFR and MTR genes are involved in folate metabolism. The folate level in the course of pregnancy is treated as vital in the etiopathogenesis of NTDs. This study aims to explore the association of SNPs of both genes and red blood cell (RBC) folate levels in the predisposition to NTDs.

Aims and Objective

The purpose of this investigation was to determine the relationship of NTDs with polymorphisms in MTHFR and MTR genotype and to estimate and compare the RBC folate levels in NTD patients and controls.

Materials and Methods

A total of 397 individuals were enrolled (163 patients and 234 controls) for this observational study. Genotyping to find out MTHFR C677T and MTR A2756G was performed by polymerase chain reaction-restriction fragment length polymorphism technique from DNA extracted from the subject's blood. RBC folate level was estimated by chemiluminescence immunoassay method with the same blood sample.

Results

The total RBC folate levels were significantly less among cases compared to controls (P = 0.020). A significant difference for RBC folate was observed between case and control groups of various genotypes of MTHFR C677T, except heterozygote CT (P = 0.459). Among MTR A2756G, genotypes with only homozygous AA have significant difference (P = 0.003) for RBC folate levels. Among different types of NTDs, there were no significant differences for RBC folate levels. Among MTHFR C677T, T allele possessed 1.9 times risk compared to C allele for the occurrence of NTDs. In MTR A2756G polymorphism, the odds of developing NTDs were 1.6 times in heterozygous AG compared to homozygous AA. Similarly, the risk for NTDs was three times higher in subjects with both heterozygous AG and CT genotypes compared to wild-type homozygous AA and CC genotypes.

Conclusion

The total RBC folate levels were significantly less among cases compared to controls, and the genotypes had no such effect in decrease in RBC folate levels. The presence of mutant allele in homozygous or heterozygous condition for both SNPs had increased risk associated with NTDs.

Synergistic Effects of Folic Acid and n-3 Polyunsaturated Fatty Acid in Preventing Neural Tube Defects in Diabetic Mice

The present study aimed to investigate whether a combination of folic acid (FA) and n-3 polyunsaturated fatty acids (PUFA) has a better preventive effect on maternal diabetes-induced neural tube defects (NTD) than FA alone. The experiment included five groups of pregnant mice: healthy control (HC), diabetes mellitus control (DMC), diabetes + n-3 PUFA (DMn-3), diabetes + FA (DMFA), and diabetes + FA + n-3 PUFA (DMFA + n-3). The incidence of NTD in DMFA + n-3 (1.04%) was significantly lower than that in DMFA (8.57%) and DMn-3 (7.82%). The incidence of NTD in DMFA and DMn-3 was significantly lower than that in DMC (19.41%). DMFA + n-3 had a lower apoptosis of neuroepithelial cells, a lower expression of P53 and Bax, and a higher expression of Pax3 and Bcl-2, compared with DMFA and DMn-3. Combination of FA and n-3 PUFA attenuated diabetes-induced hypermethylation of Pax3, overexpression and overactivity of Dnmt3b, abnormal expression of genes involved in one-carbon metabolism and elevation of homocysteine, and these improving effects were better than FA or n-3 PUFA alone. In conclusion, the combination of FA and n-3 PUFA has a synergistic effect on preventing maternal diabetes-induced NTD.

Time Course Transcriptome Analysis of Spina Bifida Progression in Fetal Rats

A better understanding of the transcriptomic modifications that occur in spina bifida may lead to identify mechanisms involved in the progression of spina bifida in utero and the development of new therapeutic strategies that aid in spinal cord regeneration after surgical interventions. In this study, RNA-sequencing was used to identify differentially expressed genes in fetal spinal cords from rats with retinoic acid-induced spina bifida at E15, E17, and E20. Gene ontology, KEGG, and protein–protein interaction analysis were conducted to predict pathways involved in the evolution of the disease. Approximately 3000, 1000 and 300 genes were differentially expressed compared to the control groups at E15, E17 and E20, respectively. Overall, the results suggest common alterations in certain pathways between gestational time points, such as upregulation in p53 and sonic hedgehog signaling at E15 and E17 and downregulation in the myelin sheath at E17 and E20. However, there were other modifications specific to gestational time points, including skeletal muscle development at E15, downregulated glucose metabolism at E17, and upregulated inflammation at E20. In conclusion, this work provides evidence that gestational age during spina bifida repair may be a significant variable to consider during the development of new regenerative therapeutics approaches.

N-3 polyunsaturated fatty acids effectively protect against neural tube defects in diabetic mice induced by streptozotocin

Folate cannot prevent all neural tube defects (NTD), indicating that other pathogeneses still exist except for the folate deficiency. Maternal diabetes mellitus during pregnancy can increase the risk of offspring NTD. Our previous study showed that polyunsaturated fatty acids (PUFA) were lower in the placenta of human NTD cases than in healthy controls, and the supplementation of fish oil (rich in long-chain (LC) n-3 PUFA, mainly C20:5n-3 and C22:6n-3) had a better prevention effect against sodium valproate induced NTD than corn oil (rich in C18:2n-6) and flaxseed oil (rich in C18:3n-3). The aim of the present study was to investigate whether PUFA could prevent diabetes-induced NTD in mice. Streptozotocin (STZ)-induced diabetic pregnant mice were fed with a normal diet (DMC), a diet containing a low dose of fish oil (DMLn-3), a diet containing a high dose of fish oil (DMHn-3) or a diet rich in corn oil (DMn-6). Healthy pregnant mice were fed with a normal diet (HC). Compared with the DMC group, the rate of NTD was significantly lower in the DMHn-3 group (4.44% vs. 12.50%), but not in the DMLn-3 (11.11%) or DMn-6 group (12.03%). The NTD rate in the DMHn-3 group was comparable with that in the HC group (1.33%) (p = 0.246), and lower than that in the DMn-6 group (p = 0.052). The NTD rate in DMLn-3 and DMn-6 groups was significantly higher than that in the HC group. No significant difference was observed in NTD rate between DMLn-3 and DMHn-3 groups, and between DMLn-3 and DMn-6 groups. Compared with the HC group, the DMC group had a significantly lower C22:6n-3 in both serum and embryos. Fish oil supplementation ameliorated neuroepithelial cell apoptosis, and the apoptotic rate was comparable between DMHn-3 and HC groups. Although the apoptotic rate was significantly lower in the DMn-6 group than the DMC group, it was still much higher than that in the HC group. The proteins P53 and Bax in embryos were higher, while the proteins Bcl-2 and Pax3 were lower in the DMC group than in the HC group. The disturbance of Pax3, P53 and Bax induced by diabetes was abolished in DMLn-3, DMHn-3 and DMn-6 groups. Importantly, Bcl-2 in embryos was restored to the normal level only in the DMHn-3 group but not in the DMLn-3 or DMn-6 group. In conclusion, LC n-3 PUFA enriched fish oil has a protective effect against NTD in diabetes induced by STZ through improving neuroepithelial cell apoptosis, and the mechanism may be by increasing the anti-apoptosis protein Bcl-2 independently of Pax3 and P53.

Identification of the Key Regulators of Spina Bifida Through Graph-Theoretical Approach

Spina Bifida (SB) is a congenital spinal cord malformation. Efforts to discern the key regulators (KRs) of the SB protein-protein interaction (PPI) network are requisite for developing its successful interventions. The architecture of the SB network, constructed from 117 manually curated genes was found to self-organize into a scale-free fractal state having a weak hierarchical organization. We identified three modules/motifs consisting of ten KRs, namely, TNIP1, TNF, TRAF1, TNRC6B, KMT2C, KMT2D, NCOA3, TRDMT1, DICER1, and HDAC1. These KRs serve as the backbone of the network, they propagate signals through the different hierarchical levels of the network to conserve the network’s stability while maintaining low popularity in the network. We also observed that the SB network exhibits a rich-club organization, the formation of which is attributed to our key regulators also except for TNIP1 and TRDMT1. The KRs that were found to ally with each other and emerge in the same motif, open up a new dimension of research of studying these KRs together. Owing to the multiple etiology and mechanisms of SB, a combination of several biomarkers is expected to have higher diagnostic accuracy for SB as compared to using a single biomarker. So, if all the KRs present in a single module/motif are targetted together, they can serve as biomarkers for the diagnosis of SB. Our study puts forward some novel SB-related genes that need further experimental validation to be considered as reliable future biomarkers and therapeutic targets.

Association of neural tube defects with maternal alterations and genetic polymorphisms in one-carbon metabolic pathway

Background

Neural tube defects (NTDs) are birth defects of the brain, spine, or spinal cord invoked by the insufficient intake of folic acid in the early stages of pregnancy and have a complex etiology involving both genetic and environmental factors. So the study aimed to explore the association between alterations in maternal one-carbon metabolism and NTDs in the offspring.

Methods

We conducted a case-control study to get a deeper insight into this association, as well as into the role of genetic polymorphisms. Plasma concentrations of folate, homocysteine (Hcy), S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH) and genotypes and alleles distributions of 52 SNPs in 8 genes were compared for 61 women with NTDs-affected offspring and 61 women with healthy ones.

Results

There were significant differences between groups with regard to plasma folate, SAM, SAH and SAM/SAH levels. Logistic regression results revealed a significant association between maternal plasma folate level and risk of NTDs in the offspring. For MTHFD1 rs2236225 polymorphism, mothers having GA genotype and A allele exhibited an increased risk of NTDs in the offspring (OR = 2.600, 95%CI: 1.227–5.529; OR = 1.847, 95%CI: 1.047–3.259). For MTHFR rs1801133 polymorphism, mothers having TT and CT genotypes were more likely to affect NTDs in the offspring (OR = 4.105, 95%CI: 1.271–13.258; OR = 3.333, 95%CI: 1.068–10.400). Moreover, mothers carrying T allele had a higher risk of NTDs in the offspring (OR = 1.798, 95%CI: 1.070–3.021). For MTRR rs1801394 polymorphism, the frequency of G allele was significantly higher in cases than in controls (OR = 1.763, 95%CI: 1.023–3.036). Mothers with NTDs-affected children had higher AG genotype in RFC1 rs1051226 polymorphism than controls, manifesting an increased risk for NTDs (OR = 3.923, 95%CI: 1.361–11.308).

Conclusion

Folic acid deficiency, MTHFD1 rs2236225, MTHFR rs1801133, MTRR rs1801349 and RFC1 rs1051226 polymorphisms may be maternal risk factors of NTDs.