A quest for genetic causes underlying signaling pathways associated with neural tube defects

MicroRNA regulation in neural tube defects: Insights into pathogenesis and potential therapeutic targets

Neural tube defects (NTDs) represent a significant burden on global pediatric health, contributing to high rates of infant mortality and morbidity. Despite extensive research into their etiology, NTDs continue to pose challenges in diagnosis and treatment. MicroRNAs (miRNAs) have emerged as promising candidates for understanding the molecular mechanisms underlying NTDs and potentially offering avenues for improved diagnosis and therapeutic intervention. This review explores the multifaceted roles of miRNAs in the context of NTD pathogenesis. Studies have identified specific miRNA profiles associated with NTDs, providing insights into their potential as diagnostic biomarkers. Furthermore, dysregulation of certain miRNAs has been implicated in the pathophysiology of NTDs, highlighting their role as potential therapeutic targets. Additionally, animal models and deep sequencing approaches have expanded our understanding of the diverse miRNA expression patterns associated with NTDs. By unraveling the intricate molecular mechanisms underlying NTD pathogenesis, miRNAs offer promising avenues for early detection and intervention, ultimately improving outcomes for affected individuals.

Biocatalytic Potential of Pseudomonas Species in the Degradation of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs), one of the major environmental pollutants, produced from incomplete combustion of materials like coal, oil, gas, wood, and charbroiled meat, that contaminate the air, soil, and water, necessitating urgent remediation. Understanding the metabolic pathways for PAHs degradation is crucial to preventing environmental damage and health issues. Biological methods are gaining increasing interest due to their cost-effectiveness and environmental friendliness. These methods are particularly suitable for remediating PAHs contamination and mitigating associated risks. The paper also outlines the processes for biodegrading PAHs, emphasizing the function of Pseudomonas spp., a kind of bacterium recognized for its capacity to degrade PAHs. To eliminate PAHs from the environment and reduce threats to human health and the environment, Pseudomonas spp. is essential. Understanding the mechanism of PAH breakdown by means of microbes could lead to effective clean-up strategies. The review highlights the enzymatic capabilities, adaptability, and genetic versatility of the genes like nah and phn of Pseudomonas spp., which are involved in PAHs degradation pathways. Scientific evidence supports using Pseudomonas spp. as biocatalysts for PAHs clean-up, offering cost-effective and eco-friendly solutions.

The DNA demethylase TET1 modifies the impact of maternal folic acid status on embryonic brain development

Folic acid (FA) is well known to prevent neural tube defects (NTDs), but we do not know why many human NTD cases still remain refractory to FA supplementation. Here, we investigate how the DNA demethylase TET1 interacts with maternal FA status to regulate mouse embryonic brain development. We determined that cranial NTDs display higher penetrance in non-inbred than in inbred Tet1-/- embryos and are resistant to FA supplementation across strains. Maternal diets that are either too rich or deficient in FA are linked to an increased incidence of cranial deformities in wild type and Tet1+/- offspring and to altered DNA hypermethylation in Tet1-/- embryos, primarily at neurodevelopmental loci. Excess FA in Tet1-/- embryos results in phospholipid metabolite loss and reduced expression of multiple membrane solute carriers, including a FA transporter gene that exhibits increased promoter DNA methylation and thereby mimics FA deficiency. Moreover, FA deficiency reveals that Tet1 haploinsufficiency can contribute to DNA hypermethylation and susceptibility to NTDs. Overall, our study suggests that epigenetic dysregulation may underlie NTD development despite FA supplementation.

Bayesian polygenic risk estimation approach to nuclear families with discordant sib-pairs for myelomeningocele

Myelomeningocele (MMC) is the most severe and disabling form of spina bifida with chronic health multisystem complications and social and economic family and health systems burden. In the present study, we aimed to investigate the genetic risk estimate for MMC in a cohort of 203 Mexican nuclear families with discordant siblings for the defect. Utilizing a custom Illumina array, we analyzed 656 single nucleotide polymorphisms (SNPs) of 395 candidate genes to identify a polygenic risk profile for MMC. Through a family-based analysis employing the transmission disequilibrium test (TDT) and Bayesian analysis, we assessed risk alleles transmission and calculated conditional probabilities estimating a polygenic risk for MMC. Our findings reveal significant associations of six genes related to neural tube closure (PSMB4, ATIC, DKK2, PSEN2, C2CD3, and PLCB2), showing differences in risk allele transmission between affected and unaffected siblings. Bayesian analysis identified changes in the risk profile after initiating folic acid fortification in Mexico, showing an evident decline in the conditional risk from 1/156 to 1/304 respectively. Despite the decline, this represents a 5.84-fold increase in risk before fortification and a 2.99-fold increase post-fortification compared to the baseline risk level (1/910). Our study highlights the advantage of incorporating a Bayesian analytical methodology in families with discordant sib-pairs, offering insights into the polygenic risk estimate for MMC and, most probably, for other congenital malformations.

Cellular responses to developmental exposure to pyriproxyfen in chicken model: Contrasting embryos with and without exencephaly

The insecticide pyriproxyfen (PPF), commonly used in drinking water, has already been described as a potential neurotoxic agent in non-target organisms, particularly during embryonic development. Consequently, exposure to PPF can lead to congenital anomalies in the central nervous system. Therefore, understanding the impact of this insecticide on developing neural cells is a relevant concern that requires attention. Thus, this study aimed to investigate the effects of PPF on the proliferation, differentiation, migration, and cell death of neural cells by comparing embryos that develop exencephaly with normal embryos, after exposure to this insecticide. Chicken embryos, used as a study model, were exposed to concentrations of 0.01 and 10 mg/L PPF on embryonic day E1 and analyzed on embryonic day E10. Exposed embryos received 50 μL of PPF diluted in vehicle solution, and control embryos received exclusively 50 μL of vehicle solution. After exposure, embryos were categorized into control embryos, embryos with exencephaly exposed to PPF, and embryos without exencephaly exposed to PPF. The results showed that although the impact was differentiated in the forebrain and midbrain, both brain vesicles were affected by PPF exposure, and this was observed in embryos with and without exencephaly. The most evident changes observed in embryos with exencephaly were DNA damage accompanied by alterations in cell proliferation, increased apoptosis, and reduced neural differentiation and migration. Embryos without exencephaly showed DNA damage and reduced cell proliferation and migration. These cellular events directly interfered with the density and thickness of neural cell layers. Together, these results suggest that PPF exposure causes cellular damage during neurogenesis, regardless of whether embryos display or do not display external normal morphology. This nuanced understanding provides important insights into the neurotoxicity of PPF and its potential effects on inherent events in neurogenesis.

PAHs as environmental pollutants and their neurotoxic effects

Polycyclic aromatic hydrocarbons (PAHs), which are widely present in incompletely combusted air particulate matter <2.5 μm (PM2.5), tobacco and other organic materials, can enter the human body through various routes and are a class of environmental pollutants with neurotoxic effects. PAHs exposure can lead to abnormal development of the nervous system and neurobehavioral abnormalities in animals, including adverse effects on the nervous system of children and adults, such as a reduced learning ability, intellectual decline, and neural tube defects. After PAHs enter cells of the nervous system, they eventually lead to nervous system damage through mechanisms such as oxidative stress, DNA methylation and demethylation, and mitochondrial autophagy, potentially leading to a series of nervous system diseases, such as Alzheimer's disease. Therefore, preventing and treating neurological diseases caused by PAHs exposure are particularly important. From the perspective of the in vitro and in vivo effects of PAHs exposure, as well as its effects on human neurodevelopment, this paper reviews the toxic mechanisms of action of PAHs and the corresponding prevention and treatment methods to provide a relevant theoretical basis for preventing the neurotoxicity caused by PAHs, thereby reducing the incidence of diseases related to the nervous system and protecting human health.

Epigenetic regulation by TET1 in gene-environmental interactions influencing susceptibility to congenital malformations

The etiology of neural tube defects (NTDs) involves complex gene-environmental interactions. Folic acid (FA) prevents NTDs, but the mechanisms remain poorly understood and at least 30% of human NTDs resist the beneficial effects of FA supplementation. Here, we identify the DNA demethylase TET1 as a nexus of folate-dependent one-carbon metabolism and genetic risk factors post-neural tube closure. We determine that cranial NTDs in Tet1 -/- embryos occur at two to three times higher penetrance in genetically heterogeneous than in homogeneous genetic backgrounds, suggesting a strong impact of genetic modifiers on phenotypic expression. Quantitative trait locus mapping identified a strong NTD risk locus in the 129S6 strain, which harbors missense and modifier variants at genes implicated in intracellular endocytic trafficking and developmental signaling. NTDs across Tet1 -/- strains are resistant to FA supplementation. However, both excess and depleted maternal FA diets modify the impact of Tet1 loss on offspring DNA methylation primarily at neurodevelopmental loci. FA deficiency reveals susceptibility to NTD and other structural brain defects due to haploinsufficiency of Tet1. In contrast, excess FA in Tet1 -/- embryos drives promoter DNA hypermethylation and reduced expression of multiple membrane solute transporters, including a FA transporter, accompanied by loss of phospholipid metabolites. Overall, our study unravels interactions between modified maternal FA status, Tet1 gene dosage and genetic backgrounds that impact neurotransmitter functions, cellular methylation and individual susceptibilities to congenital malformations, further implicating that epigenetic dysregulation may underlie NTDs resistant to FA supplementation.

Planar Cell Polarity Signaling: Coordinated Crosstalk for Cell Orientation

The planar cell polarity (PCP) system is essential for positioning cells in 3D networks to establish the proper morphogenesis, structure, and function of organs during embryonic development. The PCP system uses inter- and intracellular feedback interactions between components of the core PCP, characterized by coordinated planar polarization and asymmetric distribution of cell populations inside the cells. PCP signaling connects the anterior-posterior to left-right embryonic plane polarity through the polarization of cilia in the Kupffer's vesicle/node in vertebrates. Experimental investigations on various genetic ablation-based models demonstrated the functions of PCP in planar polarization and associated genetic disorders. This review paper aims to provide a comprehensive overview of PCP signaling history, core components of the PCP signaling pathway, molecular mechanisms underlying PCP signaling, interactions with other signaling pathways, and the role of PCP in organ and embryonic development. Moreover, we will delve into the negative feedback regulation of PCP to maintain polarity, human genetic disorders associated with PCP defects, as well as challenges associated with PCP.

Dolutegravir and Folic Acid Interaction during Neural System Development in Zebrafish Embryos

Dolutegravir (DTG) is one of the most prescribed antiretroviral drugs for treating people with HIV infection, including women of child-bearing potential or pregnant. Nonetheless, neuropsychiatric symptoms are frequently reported. Early reports suggested that, probably in relation to folic acid (FA) shortage, DTG may induce neural tube defects in infants born to women taking the drug during pregnancy. Subsequent reports did not definitively confirm these findings. Recent studies in animal models have highlighted the association between DTG exposure in utero and congenital anomalies, and an increased risk of neurologic abnormalities in children exposed during in utero life has been reported. Underlying mechanisms for DTG-related neurologic symptoms and congenital anomalies are not fully understood. We aimed to deepen our knowledge on the neurodevelopmental effects of DTG exposure and further explore the protective role of FA by the use of zebrafish embryos. We treated embryos at 4 and up to 144 h post fertilization (hpf) with a subtherapeutic DTG concentration (1 μM) and observed the disruption of the anterior-posterior axis and several morphological malformations in the developing brain that were both prevented by pre-exposure (2 hpf) and rescued by post-exposure (10 hpf) with FA. By whole-mount in situ hybridization with riboprobes for genes that are crucial during the early phases of neurodevelopment (ntl, pax2a, ngn1, neurod1) and by in vivo visualization of the transgenic Tg(ngn1:EGFP) zebrafish line, we found that DTG induced severe neurodevelopmental defects over time in most regions of the nervous system (notochord, midbrain-hindbrain boundary, eye, forebrain, midbrain, hindbrain, spinal cord) that were mostly but not completely rescued by FA supplementation. Of note, we observed the disruption of ngn1 expression in the dopaminergic regions of the developing forebrain, spinal cord neurons and spinal motor neuron projections, with the depletion of the tyrosine hydroxylase (TH)+ dopaminergic neurons of the dorsal diencephalon and the strong reduction in larvae locomotion. Our study further supports previous evidence that DTG can interfere with FA pathways in the developing brain but also provides new insights regarding the mechanisms involved in the increased risk of DTG-associated fetal neurodevelopmental defects and adverse neurologic outcomes in in utero exposed children, suggesting the impairment of dopaminergic pathways.

Surviving against the odds: exploring the clinical and radiological features of iniencephaly compatible with life. Illustrative case

BACKGROUND

Iniencephaly is a rare neural tube defect (NTD) characterized by deformities in the occiput and inion, along with rachischisis in the cervical and thoracic spine, resulting in the head appearing in retroflexion.

OBSERVATIONS

This report details the case of a female newborn who underwent surgery for an encephalocele. She survived up to 6 months, exhibiting good overall health, although she displayed physical abnormalities, including facial deformity, a short neck, and minor spasms in all limbs. Both cardiovascular and abdominal assessments remained stable, and imaging revealed defects in the occipital bone, a large cephalocele, and spinal dysraphism.

LESSONS

Although iniencephaly is generally incompatible with life, a few cases have been reported otherwise. Our patient, one of these notable exceptions, remains alive at 6 months old, possibly due to the lack of major vascular deformities. However, she does exhibit significant psychomotor retardation.