Moderately high intake of folic acid has a negative impact on mouse embryonic development

BACKGROUND

The incidence of neural tube defects has diminished considerably since the implementation of food fortification with folic acid (FA). However, the impact of excess FA intake, particularly during pregnancy, requires investigation. In a recent study, we reported that a diet supplemented with 20‐fold higher FA than the recommended intake for rodents had adverse effects on embryonic mouse development at embryonic days (E)10.5 and 14.5. In this report, we examined developmental outcomes in E14.5 embryos after administering a diet supplemented with 10‐fold higher FA than recommended to pregnant mice with and without a mild deficiency of methylenetetrahydrofolate reductase (MTHFR).

METHODS

Pregnant mice with or without a deficiency in MTHFR were fed a control diet (recommended FA intake of 2 mg/kg diet for rodents) or an FA‐supplemented diet (FASD; 10‐fold higher than the recommended intake [20 mg/kg diet]). At E14.5, mice were examined for embryonic loss and growth retardation, and hearts were assessed for defects and for ventricular wall thickness.

RESULTS

Maternal FA supplementation was associated with embryonic loss, embryonic delays, a higher incidence of ventricular septal defects, and thinner left and right ventricular walls, compared to mothers fed control diet.

CONCLUSIONS

Our work suggests that even moderately high levels of FA supplementation may adversely affect fetal mouse development. Additional studies are warranted to evaluate the impact of high folate intake in pregnant women. Birth Defects Research (Part A), 2013. © 2012 Wiley Periodicals, Inc.     

Effects of Estrogen Coadministration on Epoxiconazole Toxicity in Rats

Epoxiconazole (EPX; CAS‐No. 133855‐98‐8) is a triazole class–active substance of plant protection products. At a dose level of 50 mg/kg bw/day, it causes a significantly increased incidence of late fetal mortality when administered to pregnant rats throughout gestation (gestation day [GD] 7–18 or 21), as reported previously (Taxvig et al., 2007, 2008) and confirmed in these studies. Late fetal resorptions occurred in the presence of significant maternal toxicity such as clear reduction of corrected body weight gain, signs of anemia, and, critically, a marked reduction of maternal estradiol plasma levels. Furthermore, estradiol supplementation at dose levels of 0.5 or 1.0 μg/animal/day of estradiol cyclopentylpropionate abolished the EPX‐mediated late fetal resorptions. No increased incidences of external malformations were found in rats cotreated with 50 mg/kg bw/day EPX and estradiol cyclopentylpropionate, indicating that the occurrence of malformations was not masked by fetal mortality under the study conditions. Overall, the study data indicate that fetal mortality observed in rat studies with EPX is not the result of direct fetal toxicity but occurs indirectly via depletion of maternal estradiol levels. The clarification of the human relevance of the estrogen‐related mechanism behind EPX‐mediated late fetal resorptions in rats warrants further studies. In particular, this should involve investigation of the placenta (Rey Moreno et al., 2013), since it is the materno‐fetal interface and crucial for fetal maintenance. The human relevance is best addressed in a species which is closer to humans with reference to placentation and hormonal regulation of pregnancy, such as the guinea pig (Schneider et al., 2013). Birth Defects Res (Part B) 98:247–259, 2013. © 2013 Wiley Periodicals, Inc.     

Establishment and Assessment of a New Human Embryonic Stem Cell‐Based Biomarker Assay for Developmental Toxicity Screening

A metabolic biomarker‐based in vitro assay utilizing human embryonic stem (hES) cells was developed to identify the concentration of test compounds that perturbs cellular metabolism in a manner indicative of teratogenicity. This assay is designed to aid the early discovery‐phase detection of potential human developmental toxicants. In this study, metabolomic data from hES cell culture media were used to assess potential biomarkers for development of a rapid in vitro teratogenicity assay. hES cells were treated with pharmaceuticals of known human teratogenicity at a concentration equivalent to their published human peak therapeutic plasma concentration. Two metabolite biomarkers (ornithine and cystine) were identified as indicators of developmental toxicity. A targeted exposure‐based biomarker assay using these metabolites, along with a cytotoxicity endpoint, was then developed using a 9‐point dose–response curve. The predictivity of the new assay was evaluated using a separate set of test compounds. To illustrate how the assay could be applied to compounds of unknown potential for developmental toxicity, an additional 10 compounds were evaluated that do not have data on human exposure during pregnancy, but have shown positive results in animal developmental toxicity studies. The new assay identified the potential developmental toxicants in the test set with 77% accuracy (57% sensitivity, 100% specificity). The assay had a high concordance (≥75%) with existing in vivo models, demonstrating that the new assay can predict the developmental toxicity potential of new compounds as part of discovery phase testing and provide a signal as to the likely outcome of required in vivo tests.     

An assessment of gene‐by‐environment interactions in developmental dyslexia‐related phenotypes

While the genetic and environmental contributions to developmental dyslexia (DD) have been studied extensively, the effects of identified genetic risk susceptibility and of specified environmental hazardous factors have usually been investigated separately. We assessed potential gene‐by‐environment (GxE) interactions on DD‐related reading, spelling and memory phenotypes. The presence of GxE effects were investigated for the DYX1C1, DCDC2, KIAA0319 and ROBO1 genes, and for seven specified environmental moderators in 165 nuclear families in which at least one member had DD, by implementing a general test for GxE interaction in sib‐pair‐based association analysis of quantitative traits. Our results support a diathesis‐stress model for both reading and memory composites: GxE effects were found between some specified environmental moderators (i.e. maternal smoke during pregnancy, birth weight and socio‐economic status) and the DYX1C1‐1259C/G marker. We have provided initial evidence that the joint analysis of identified genetic risk susceptibility and measured putative risk factors can be exploited in the study of the etiology of DD and reading‐related neuropsychological phenotypes, and may assist in identifying/preventing the occurrence of DD.     

The plasma zinc/serum copper ratio as a biomarker in children with autism spectrum disorders

The frequency of zinc deficiency, copper toxicity and low zinc/copper in children with autism spectrum disorders (ASDs) may indicate decrement in metallothionein system functioning. A retrospective review of plasma zinc, serum copper and zinc/copper was performed on data from 230 children with autistic disorder, pervasive developmental disorder-NOS and Asperger’s syndrome. The entire cohort’s mean zinc level was 77.2 μg dl^?1, mean copper level was 131.5 μg dl^?1, and mean Zn/Cu was 0.608, which was below the 0.7 cut-off of the lowest 2.5% of healthy children. The plasma zinc/serum copper ratio may be a biomarker of heavy metal, particularly mercury, toxicity in children with ASDs.     

Raman Spectroscopy: A Conformational Probe in Biochemistr

RNA localization, the enrichment of RNA in a specific subcellular region, is a mechanism for the establishment and maintenance of cellular polarity in a variety of systems. Ultimately, this results in a universal method for spatially restricting gene expression. Although the consequences of RNA localization are well-appreciated, many of the mechanisms that are responsible for carrying out polarized transport remain elusive. Several recent studies have illuminated the roles that molecular motor proteins play in the process of RNA localization. These studies have revealed complex mechanisms in which the coordinated action of one or more motor proteins can act at different points in the localization process to direct RNAs to their final destination. In this review, we discuss recent findings from several different systems in an effort to clarify pathways and mechanisms that control the directed movement of RNA.     

GM plants as sources of im/possibility: a developmental systems view of stabilization

This paper generates a heuristic understanding of the stabilization dynamic of genetically modified plants. This heuristic, the paper argues, can provide a fruitful platform for studying the political dimensions embedded in GM plants. Focusing on stabilization is important, because outside laboratories a plant can have an intermediating role only as a cultivar; as something which has integrated into biological processes and human practices. The actual stabilizing entity is not just an object, but a dynamic analogous to what is called a developmental system. The empowering or suppressing consequences of GM plants depend significantly on the qualities of this spatio-temporal order stabilizing; on the “possibility space” it opens up. Moreover, stabilization connects and makes things possible, but it does not do so automatically, predictably – or for everyone. Centralized control may support stability, but it may also increase vulnerability by reducing local possibility space.     

Genesis of phenotypic and genotypic diversity in land plants: The present as the key to the past

The evolutionary history of vascular plants is reviewed by extrapolation back through time from a wide range of data recently derived from the present flora, using as the central theme evolutionary inferences gained from phylogenies reconstructed as cladograms. Any region of the genome can be used to infer relationships, but only a combination of knowledge of morphology and the developmental genes that underpin morphology can allow evolutionary interpretation of macroevolutionary transitions; this in turn is necessary to identify bona fide evolutionary radiations and any putative causal key innovations. Such studies require clades to be delimited not by the inclusion of particular extant ‘crown’ species but rather by specific apo‐morphies, thereby giving important phylogenetic roles to extinct as well as extant species. Dating phylogenetic divergences via molecular clocks remains seriously inaccurate, and ultimately relies primarily on fossil benchmarks. First principles suggest that evolution of most regions of the genome is fundamentally gradual, whereas evolution of regions especially prone to strong selection pressure, and of the many facets of the phenotype, is punctuational, being characterized through time dominantly by stasis. Sequence data have proved valuable for inferring monophyletic groups, but within the now widely accepted context of monophyly the taxonomic hierarchy should primarily reflect degrees of morphological rather than molecular divergence. Incongruence among contrasting data sets is best explained by understanding the biological constraints operating on each type of phylogenetic information. The conventional ‘uniformitarian’ view of evolution has only limited applicability as one traces the history of land plants through time. Diversity increased in stepwise fashion, reflecting either attainments of complexity and/or fitness thresholds by the lineage (intrinsic) or the availability of unusually permissive environments, often following major perturbations (extrinsic). The Quaternary period demonstrates especially well the resilience, and ease of migration, of the Earth's vegetation. A higher frequency of generation of novel phenotypes in the deep past is possible, but a far higher frequency of their establishment is certain; together, these factors generate an evolutionary pattern of nested radiations that is fractal, as saturation of the resource space rendered the environment decreasingly permissive through time. In the immediate future, evolutionary‐developmental genetics will have increasing value for testing homology, interpreting homoplasy and elucidating evolutionary constraints, and will become easier to pursue as whole‐genome sequences of additional ‘model’ species further invigorate comparative genomics. Complexity of gene regulation, both by other genes and by the cellular and extra‐cellular environment, appears a particularly fruitful area for further research. Nonetheless, environmental filtering of evolutionary novelties (whether instantaneously isolated mutant ‘prospecies’ or classic neoDarwinian ‘selfish genes’ selectively spreading through panmictic populations) can only be effectively understood by longer term monitoring of populations in the wild, to better capture rare evolutionary and ecological events and to better assess the efficacy of traditional microevolutionary processes. We believe that the resulting renaissance in macroevolutionary studies will encourage a broader systematic perspective ‐ one that better encompasses the remarkable diversity of evolutionary processes that together generated the present diversity of life.     

Orchestration of tissue‐scale mechanics and fate decisions by polarity signalling

Eukaryotic development relies on dynamic cell shape changes and segregation of fate determinants to achieve coordinated compartmentalization at larger scale. Studies in invertebrates have identified polarity programmes essential for morphogenesis; however, less is known about their contribution to adult tissue maintenance. While polarity‐dependent fate decisions in mammals utilize molecular machineries similar to invertebrates, the hierarchies and effectors can differ widely. Recent studies in epithelial systems disclosed an intriguing interplay of polarity proteins, adhesion molecules and mechanochemical pathways in tissue organization. Based on major advances in biophysics, genome editing, high‐resolution imaging and mathematical modelling, the cell polarity field has evolved to a remarkably multidisciplinary ground. Here, we review emerging concepts how polarity and cell fate are coupled, with emphasis on tissue‐scale mechanisms, mechanobiology and mammalian models. Recent findings on the role of polarity signalling for tissue mechanics, micro‐environmental functions and fate choices in health and disease will be summarized.     

Larval growth and allometry in the cabbage butterfly Pieris brassicae (Lepidoptera: Pieridae)

By adopting a longitudinal study design and through geometric morphometrics methods, we investigated individual and ontogenetic variation in size, shape and timing during larval development of the cabbage butterfly Pieris brassicae under laboratory conditions. We found that ontogenetic size progression departs modestly, but significantly, from growth at a constant rate and that size at hatching contributes considerably to determine the size of the individual at all subsequent stages. As for the shape, ontogenetic allometry is much more conspicuous than static allometry, the latter in many cases being close to isometry. Analysis of developmental timing revealed a stage of apparently more effective developmental control at stage 3, supported by both the relatively small variance in cumulative developmental time up to stage 3 and by the pattern of correlation between duration of single stages. While presenting detailed quantitative aspects of growth in P. brassicae, in particular with respect to individual variation, this study and the associated dataset can provide a basis for further explorations of the post‐embryonic development in this insect and contribute to the ongoing investigations on growth regulation and control in insects.