The common house spider Parasteatoda tepidariorum

The common house spider Parasteatoda tepidariorum, belonging to the Chelicerata in the phylum Arthropoda, has emerged as an experimental system for studying mechanisms of development from an evolutionary standpoint. In this article, we review the distinct characteristics of P. tepidariorum, the major research questions relevant to this organism, and the available key methods and resources. P. tepidariorum has a relatively short lifecycle and, once mated, periodically lays eggs. The morphogenetic field of the P. tepidariorum embryo is cellular from an early stage and exhibits stepwise symmetry-breaking events and stripe-forming processes that are associated with body axes formation and segmentation, respectively, before reaching the arthropod phylotypic stage. Self-regulatory capabilities of the embryonic field are a prominent feature in P. tepidariorum. The mechanisms and logic underlying the evolvability of heritable patterning systems at the phylum level could be one of the major avenues of research investigated using this animal. The sequenced genome reveals whole genome duplication (WGD) within chelicerates, which offers an invertebrate platform for investigating the potential roles of WGD in animal diversification and evolution. The development and evolution of lineage-specific organs, including the book lungs and the union of spinnerets and silk glands, are attractive subjects of study. Studies using P. tepidariorum can benefit from the use of parental RNA interference, microinjection applications (including cell labeling and embryonic RNA interference), multicolor fluorescence in situ hybridization, and laser ablation as well as rich genomic and transcriptomic resources. These techniques enable functional gene discoveries and the uncovering of cellular and molecular insights.

Developmental toxicity of fipronil in early development of zebrafish (Danio rerio) larvae: Disrupted vascular formation with angiogenic failure and inhibited neurogenesis

Fipronil has been widely used in agriculture to prevent aggressive insects from damaging agricultural products. Fipronil residues circulate in the environment and they have been detected in non-targeted organisms in aquatic environments. To study the effect of fipronil toxicity on environmental health, 6 h post fertilization (hpf) zebrafish embryos were treated with fipronil for 72 h. LC₅₀ value was obtained by applying varying concentrations of fipronil to zebrafish embryos for 72 h. As zebrafish embryos are useful vertebrate models for studying developmental and genetic findings in toxicology research, they were exposed to fipronil to study detailed elucidating mechanisms with hazardous end points of toxicity. Cell cycle arrest-related apoptosis supported pathological alterations, such as increased mortality, shortened body length, and reduced hatchability. Furthermore, observed heart defects, including edema and irregular heartbeat were caused due to abnormal blood circulation. In transgenic zebrafish models (fli1:eGFP and olig2:dsRED), disrupted blood vessel formations were indicated by eGFP⁺ endothelial cells. Moreover, neurogenic defects were observed by studying dsRED⁺ motor neurons and oligodendrocytes. This study demonstrates fipronil accumulation in aquatic environment and its ability to impair essential processes, such as angiogenesis and neurogenesis during early developmental stage of zebrafish, along with general developmental toxicity.

Changes of cell wall components during embryogenesis of Castanea mollissima

The Chinese chestnut (Castanea mollissima Blume) 'Huaihuang' was chosen as the experimental material to observe embryogenesis and the dynamic changes of cell wall components during this process. Various developmental stages of embryos, including globular embryos, heart embryos, torpedo embryos and cotyledon embryos, were observed. The results showed that during embryogenesis, cellulose increased, and callose rapidly degraded. In the cell walls of developing embryos, pectic homogalacturonan (HG), especially low-esterified HG, was abundant, suggesting rapid synthesis and de-methyl-esterification of HG. Extensin and galactan increased with the development of the embryos. In contrast, the arabinan epitopes decreased in developing embryos but were more abundant than galactan epitopes at all stages. Xylan epitopes showed explicit boundaries between the outer epidermal wall and the rest of the inner tissues, and the fluorescence intensity of the outer epidermal wall was significantly higher than that of the inner tissues. Furthermore, the results indicated that the outer epidermal wall contained high amounts of cellulose, HG pectin and hemicellulose, especially arabinan and xylan. These results suggested the presence of rapid pectin metabolism, cellulose synthesis, rapid degradation of callose, different distributive patterns and dynamic changes of hemicellulose (galactan, arabinan and xylan) and extensin during embryogenesis. Various cell wall components exist in different tissues of the embryo, and dynamic changes in cell wall components are involved in the embryonic development process.

Development stage of cryopreserved mussel (Perna canaliculus) larvae influences post-thaw impact on shell formation, organogenesis, neurogenesis, feeding ability and survival

Cryopreservation of genetic material from farmed aquatic species is a valuable technique to advance selective breeding programs for stock improvement. In this study, effects of cryopreservation on development of trochophore and D-stage larvae of Greenshell™ mussel (Perna canaliculus) were evaluated through histology, light microscopy, scanning electron microscopy, and confocal microscopy. Larvae of both life stages were motile immediately post-thawing, but survival declined rapidly from 4 days post-fertilisation (dpf). At 18 dpf, ~23% of non-cryopreserved control larvae had progressed to the pediveliger stage, while <1% of cryopreserved larvae had survived. Control larvae grew faster and larger, and consumed more food than larvae cryopreserved at either life stage (trochophore or D-stage). Settlement competency was achieved in the control larvae at 21 days post-fertilization, with most remaining individuals developing eye spots. Organogenesis was delayed in all cryopreserved larvae, and eyespots did not appear at all. Neurogenesis was stunted in cryopreserved trochophore larvae but seemed to progress almost normally in their cryopreserved D-stage counterparts. Developing abnormalities in shell morphology rapidly became apparent in all mussels post-thaw, with trochophore larvae being most highly afflicted. These delays in organogenesis and overall development are indicative of cryo-injuries sustained at a cellular level. Our results show that D-stage larvae are somewhat more resilient to cryopreservation than trochophore larvae. D-larvae are good life-stage candidates for cryobanking genetic resources in this species because there is generally an excess of larvae from selective breeding family crosses and these can be banked and stored for later use. Further on-going research aims to improve the long-term viability of cryopreserved D-larvae for successful rearing.

Investigation of three enzymes and their roles in the embryonic development of parthenogenetic Haemaphysalis longicornis

BACKGROUND

The tick Haemaphysalis longicornis exhibits two separate reproductive populations: bisexual and parthenogenetic, which have diploid and triploid karyotypes, respectively. The parthenogenetic population can undergo engorgement without copulation and produce viable female-only offspring with a longer incubation period than the bisexual population. Three enzymes, cathepsin B, cathepsin D and acid phosphatase, were found to be involved in vitellin degradation during the embryonic development of bisexual H. longicornis. However, the expression and activity profiles of these enzymes during the embryonic development of parthenogenetic ticks remain unknown. In the present study, the transcriptional expression profile, enzyme activity and roles in embryogenesis of the three enzymes during the embryonic development of parthenogenetic H. longicornis were investigated.

METHODS

Quantitative real-time polymerase chain reaction (qPCR) and fluorescence detection were used to analyze the dynamic changes in the three enzymes during embryogenesis. The roles of the three enzymes during embryogenesis were also explored using RNA interference (RNAi).

RESULTS

The three enzymes were all expressed during embryonic development in parthenogenetic H. longicornis. The expression of cathepsin B was highest on day 15, whereas that of cathepsin D was highest on day 3 and the peak of acid phosphatase expression occurred on day 9. The activity of cathepsin B was highest on day 3 and lowest on day 5, then gradually increased and remained stable. Cathepsin D activity was highest on day 1 and showed a gradually decreasing trend, whereas acid phosphatase showed the opposite trend and reached a peak on day 23. RNA interference experiments in engorged female ticks revealed that there was no significant difference in the number of eggs laid, but the hatching rate of the eggs was significantly decreased.

CONCLUSION

The three enzymes all play important roles in embryonic development of H. longicornis, but the expression patterns and changes in the activity of the enzymes in the bisexual and parthenogenetic populations are different. The results will help a better understanding of the similarities and differences underlying embryonic development in the bisexual and parthenogenetic populations and contribute to the future exploration of the development of the parthenogenetic population of H. longicornis.

Imaging of Embryo Sac and Early Seed Development in Maize after Feulgen Staining

Compared with small model plants like Arabidopsis containing ovules with few cell layers, embryo sac and embryo development of model crop plants such as maize and other grasses are difficult to image. Multiple layers of tissue usually surround the deeply embedded embryo sac and developing embryo. Moreover, reliable cell biological marker lines labeling, for example, nuclei, plasma membrane, cell walls, or cells of a specific identity are often not available. The introduction of markers to study mutants is difficult and time-consuming and may require several generations of backcrosses. In this chapter, we therefore present an easy protocol to image maize ovaries and developing embryo sacs before and after fertilization allowing also high-throughput mutant analysis. The laborious embedding of samples and preparation of thin sections are omitted in this fixing-Feulgen staining-clearing (FFC) method. Optical sectioning through multiple layers of tissue is possible allowing 3D reconstructions of the whole embryo sac if necessary. The advantage of staining cell nuclei using the FFC method described here compared, for example, with DAPI staining is a wide range of Schiff's type reagents available for the Feulgen reaction. Depending on the reagent of choice, various conditions such as different excitation/emission filters or even white light can be applied for imaging. Moreover, in order to better visualize cell division, nuclei polarity as well as cell extent and integrity, periodic acid staining (PAS) of cell walls can be combined with Feulgen staining.

Analyzing Subcellular Reorganization During Early Arabidopsis Embryogenesis Using Fluorescent Markers

Virtually all growth, developmental, physiological, and defense responses in plants are accompanied by reorganization of subcellular structures to enable altered cellular growth, differentiation or function. Visualizing cellular reorganization is therefore critical to understand plant biology at the cellular scale. Fluorescently labeled markers for organelles, or for cellular components are widely used in combination with confocal microscopy to visualize cellular reorganization. Early during plant embryogenesis, the precursors for all major tissues of the seedling are established, and in Arabidopsis, this entails a set of nearly invariant switches in cell division orientation and directional cell expansion. Given that these cellular reorganization events are genetically regulated and coupled to formative events in plant development, they offer a good model to understand the genetic control of cellular reorganization in plant development. Until recently, it has been challenging to visualize subcellular structures in the early Arabidopsis embryo for two reasons: embryos are deeply embedded in seed coat and fruit, and in addition, no dedicated fluorescent markers, expressed in the embryo, were available. We recently established both an imaging approach and a set of markers for the early Arabidopsis embryo. Here, we describe a detailed protocol to use these new tools in imaging cellular reorganization.

Fetal Alcohol Spectrum Disorder: Embryogenesis Under Reduced Retinoic Acid Signaling Conditions

Fetal Alcohol Spectrum Disorder (FASD) is a complex set of developmental malformations, neurobehavioral anomalies and mental disabilities induced by exposing human embryos to alcohol during fetal development. Several experimental models and a series of developmental and biochemical approaches have established a strong link between FASD and reduced retinoic acid (RA) signaling. RA signaling is involved in the regulation of numerous developmental decisions from patterning of the anterior-posterior axis, starting at gastrulation, to the differentiation of specific cell types within developing organs, to adult tissue homeostasis. Being such an important regulatory signal during embryonic development, mutations or environmental perturbations that affect the level, timing or location of the RA signal can induce multiple and severe developmental malformations. The evidence connecting human syndromes to reduced RA signaling is presented here and the resulting phenotypes are compared to FASD. Available data suggest that competition between ethanol clearance and RA biosynthesis is a major etiological component in FASD.

Does microplastic ingestion by zooplankton affect predator-prey interactions? An experimental study on larviphagy

Litter is omnipresent in the ocean where it can be ingested by marine biota. Although ingestion of microplastics (MPs) is abundantly reported, insights into how MP can influence predator-prey interactions currently limits our understanding of the ecological impact of MPs. Here we demonstrate trophic transfer of MPs from zooplankton to benthic filter feeders, through consumption of contaminated prey (i.e. prey with ingested MP). However, predation rates of contaminated prey were significantly lower as compared to predation rates of prey that had no MPs ingested. As filter feeder clearance rates were not affected by consumption of MPs, the lower predation rates of contaminated prey appear to be primarily explained by disruption in zooplankton swimming behaviour that reduces their filtration risk. This is the first study that shows how MPs can change predator-prey interactions that are involved in the coupling between the pelagic and seabed habitat.

Isolated Microspore Culture in Brassica napus

Isolated microspore culture is the most efficient technique among those used to induce microspore embryogenesis. In the particular case of Brassica napus, it is also the most widely used and optimized. In this chapter, we describe a protocol for microspore culture in B. napus which includes the steps necessary to isolate and culture microspores, to induce microspore-derived embryos, to produce doubled haploid plants from them, as well as to check for the developmental stage of the microspores isolated, their viability, and the ploidy level of regenerated plantlets.

Maternal-Fetal Transfer of Vitamin A and Its Impact on Mammalian Embryonic Development

The placenta, a hallmark of mammalian embryogenesis, allows nutrients to be exchanged between the mother and the fetus. Vitamin A (VA), an essential nutrient, cannot be synthesized by the embryo, and must be acquired from the maternal circulation through the placenta. Our understanding of how this transfer is accomplished is still in its infancy. In this chapter, we recapitulate the early studies about the relationship between maternal dietary/supplemental VA intake and fetal VA levels. We then describe how the discovery of retinol-binding protein (RBP or RBP4), the development of labeling and detection techniques, and the advent of knockout mice shifted this field from a macroscopic to a molecular level. The most recent data indicate that VA and its derivatives (retinoids) and the pro-VA carotenoid, β-carotene, are transferred across the placenta by distinct proteins, some of which overlap with proteins involved in lipoprotein uptake. The VA status and dietary intake of the mother influence the expression of these proteins, creating feedback signals that control the uptake of retinoids and that may also regulate the uptake of lipids, raising the intriguing possibility of crosstalk between micronutrient and macronutrient metabolism. Many questions remain about the temporal and spatial patterns by which these proteins are expressed and transferred throughout gestation. The answers to these questions are highly relevant to human health, considering that those with either limited or excessive intake of retinoids/carotenoids during pregnancy may be at risk of obtaining improper amounts of VA that ultimately impact the development and health of their offspring.

A Novel LINS1 Truncating Mutation in Autosomal Recessive Nonsyndromic Intellectual Disability

The large majority of cases with intellectual disability are syndromic (i.e. occur with other well-defined clinical phenotypes) and have been studied extensively. Autosomal recessive nonsyndromic intellectual disability is a group of genetically heterogeneous disorders for which a number of potentially causative genes have been identified although the molecular basis of most of them remains unexplored. Here, we report the clinical characteristics and genetic findings of a family with two male siblings affected with autosomal recessive nonsyndromic intellectual disability. Whole exome sequencing was carried out on two affected male siblings and unaffected parents. A potentially pathogenic variant identified in this study was confirmed by Sanger sequencing to be inherited in an autosomal recessive fashion. We identified a novel nonsense mutation (p.Gln368Ter) in the LINS1 gene which leads to loss of 389 amino acids in the C-terminus of the encoded protein. The truncation mutation causes a complete loss of LINES_C domain along with loss of three known phosphorylation sites and a known ubiquitylation site in addition to other evolutionarily conserved regions of LINS1. LINS1 has been reported to cause MRT27 (mental retardation, autosomal recessive 27), a rare autosomal recessive nonsyndromic intellectual disability, with limited characterization of the phenotype. Identification of a potentially pathogenic truncating mutation in LINS1 in two profoundly intellectually impaired patients also confirms its role in cognition.

Optogenetic approaches to investigate spatiotemporal signaling during development

Embryogenesis is coordinated by signaling pathways that pattern the developing organism. Many aspects of this process are not fully understood, including how signaling molecules spread through embryonic tissues, how signaling amplitude and dynamics are decoded, and how multiple signaling pathways cooperate to pattern the body plan. Optogenetic approaches can be used to address these questions by providing precise experimental control over a variety of biological processes. Here, we review how these strategies have provided new insights into developmental signaling and discuss how they could contribute to future investigations.

Combinatorial action of NF-Y and TALE at embryonic enhancers defines distinct gene expression programs during zygotic genome activation in zebrafish

Animal embryogenesis is initiated by maternal factors, but zygotic genome activation (ZGA) shifts regulatory control to the embryo during blastula stages. ZGA is thought to be mediated by maternally provided transcription factors (TFs), but few such TFs have been identified in vertebrates. Here we report that NF-Y and TALE TFs bind zebrafish genomic elements associated with developmental control genes already at ZGA. In particular, co-regulation by NF-Y and TALE is associated with broadly acting genes involved in transcriptional control, while regulation by either NF-Y or TALE defines genes in specific developmental processes, such that NF-Y controls a cilia gene expression program while TALE controls expression of hox genes. We also demonstrate that NF-Y and TALE-occupied genomic elements function as enhancers during embryogenesis. We conclude that combinatorial use of NF-Y and TALE at developmental enhancers permits the establishment of distinct gene expression programs at zebrafish ZGA.

Molecular patterning during the development of Phoronopsis harmeri reveals similarities to rhynchonelliform brachiopods

BACKGROUND

Phoronids, rhynchonelliform and linguliform brachiopods show striking similarities in their embryonic fate maps, in particular in their axis specification and regionalization. However, although brachiopod development has been studied in detail and demonstrated embryonic patterning as a causal factor of the gastrulation mode (protostomy vs deuterostomy), molecular descriptions are still missing in phoronids. To understand whether phoronids display underlying embryonic molecular mechanisms similar to those of brachiopods, here we report the expression patterns of anterior (otx, gsc, six3/6, nk2.1), posterior (cdx, bra) and endomesodermal (foxA, gata4/5/6, twist) markers during the development of the protostomic phoronid Phoronopsis harmeri.

RESULTS

The transcription factors foxA, gata4/5/6 and cdx show conserved expression in patterning the development and regionalization of the phoronid embryonic gut, with foxA expressed in the presumptive foregut, gata4/5/6 demarcating the midgut and cdx confined to the hindgut. Furthermore, six3/6, usually a well-conserved anterior marker, shows a remarkably dynamic expression, demarcating not only the apical organ and the oral ectoderm, but also clusters of cells of the developing midgut and the anterior mesoderm, similar to what has been reported for brachiopods, bryozoans and some deuterostome Bilateria. Surprisingly, brachyury, a transcription factor often associated with gastrulation movements and mouth and hindgut development, seems not to be involved with these patterning events in phoronids.

CONCLUSIONS

Our description and comparison of gene expression patterns with other studied Bilateria reveals that the timing of axis determination and cell fate distribution of the phoronid shows highest similarity to that of rhynchonelliform brachiopods, which is likely related to their shared protostomic mode of development. Despite these similarities, the phoronid Ph. harmeri also shows particularities in its development, which hint to divergences in the arrangement of gene regulatory networks responsible for germ layer formation and axis specification.

Cryopreservation: A tool to conserve date palm in Saudi Arabia

The cryostoring of embryogenic tissue of the date palm (Phoenix dactylifera L. cv. Sagai) was examined through dehydrated-encapsulation, vitrification, and vitrification-encapsulation. The most extreme regeneration rate (53.33%) of epitomized, cryostored liquid nitrogen (+LN) treated embryos was observed when pre-embryonic masses were hatched with 0.5 M sucrose for 48 h pursued by 6 h air drying out. The most noteworthy survival rate (80.0%) of epitomized, cryopreserved embryonic cluster came about when calli were hatched with 0.3 or 0.7 M sucrose for 48 h pursued by four hours of lack of hydration, or with 0.5 M sucrose for 48 h without air drying out or with 2 h of air drying out. Following cryopreservation utilizing the embodiment vitrification convention, the most astounding survival (86.7%) as well as the greatest growth (46.7%) was accomplished when the typified vitrified, cryopreserved calli were treated with Vitrification Solution 2 for plants (PVS2) for 60 min at 25 °C. Cryopreservation utilizing the vitrification convention brought about the most extreme recuperation of 53.3%, when vitrified-cryopreserved calli were subjected to PVS2 solution for 30 min at 25 °C. Most extreme (40%) regeneration of vitrified, cryopreserved embryonic calli was seen when these calli were treated with PVS2 solution for 60 min at 25 °C. The outcome got amid this investigation of regrowth after cryopreservation of the cv. Sagai was over the base suitable for a cryo-germplasm bank. Recovery and regrowth were above 30% for all the techniques developed for the cv. Sagai.

Exploratory analysis of transposable elements expression in the C. elegans early embryo

BACKGROUND

Transposable Elements (TE) are mobile sequences that make up large portions of eukaryote genomes. The functions they play within the complex cellular architecture are still not clearly understood, but it is becoming evident that TE have a role in several physiological and pathological processes. In particular, it has been shown that TE transcription is necessary for the correct development of mice embryos and that their expression is able to finely modulate transcription of coding and non-coding genes. Moreover, their activity in the central nervous system (CNS) and other tissues has been correlated with the creation of somatic mosaicisms and with pathologies such as neurodevelopmental and neurodegenerative diseases as well as cancers.

RESULTS

We analyzed TE expression among different cell types of the Caenorhabditis elegans (C. elegans) early embryo asking if, where and when TE are expressed and whether their expression is correlated with genes playing a role in early embryo development. To answer these questions, we took advantage of a public C. elegans embryonic single-cell RNA-seq (sc-RNAseq) dataset and developed a bioinformatics pipeline able to quantify reads mapping specifically against TE, avoiding counting reads mapping on TE fragments embedded in coding/non-coding transcripts. Our results suggest that i) canonical TE expression analysis tools, which do not discard reads mapping on TE fragments embedded in annotated transcripts, may over-estimate TE expression levels, ii) Long Terminal Repeats (LTR) elements are mostly expressed in undifferentiated cells and might play a role in pluripotency maintenance and activation of the innate immune response, iii) non-LTR are expressed in differentiated cells, in particular in neurons and nervous system-associated tissues, and iv) DNA TE are homogenously expressed throughout the C. elegans early embryo development.

CONCLUSIONS

TE expression appears finely modulated in the C. elegans early embryo and different TE classes are expressed in different cell types and stages, suggesting that TE might play diverse functions during early embryo development.

Structural aspects of cypsela and seed development of Trichocline catharinensis (Cabrera): a Brazilian endemic species

This is the first study to describe in a timescale morphohistological and ultrastructural characteristics of fruit (cypsela) and seed development in Trichocline catharinensis, which was completed 21 days after anthesis (DAA). At anthesis, we identified an ovary with three differentiated regions, including the inner epidermis, inner part, and outer epidermis. The mature ovule showed an integument with the outer epidermis, integumentary parenchyma, and endothelium. Cells around the endothelium form the periendothelial zone with thick cell walls that showed Periodic acid-Schiff (PAS)-positive reaction. The periendothelial zone and endothelium showed degradation of the cells during embryogenesis. The main stages of embryo development from fecundation through mature seed were identified. The ripe cypsela showed the pericarp (exocarp), seed coat (exotesta), and remaining endosperm surrounding the embryo. Mature embryos were straight with shoot apical meristem (SAM), and root apical meristem (RAM) was separated by the hypocotyl. Light microscopy (LM) and transmission electron microscopy (TEM) analyses indicate cells with characteristics of meristem cells, as well as proteins and lipid bodies and mitochondria with few cristae in cotyledon cells. Our findings provide insight into taxonomic and physiological studies by detailing cypsela and seed ontogenesis from an endemic and vulnerable Asteraceae from southern Brazil. This study is also a starting point for establishing the biological criteria for seed harvesting and future studies of seed physiology and conservation of plant genetic resource.

Distinct functions and temporal regulation of methylated histone H3 during early embryogenesis

During the first hours of embryogenesis, formation of higher-order heterochromatin coincides with the loss of developmental potential. Here, we examine the relationship between these two events, and we probe the processes that contribute to the timing of their onset. Mutations that disrupt histone H3 lysine 9 (H3K9) methyltransferases reveal that the methyltransferase MET-2 helps terminate developmental plasticity, through mono- and di-methylation of H3K9 (me1/me2), and promotes heterochromatin formation, through H3K9me3. Although loss of H3K9me3 perturbs formation of higher-order heterochromatin, embryos are still able to terminate plasticity, indicating that the two processes can be uncoupled. Methylated H3K9 appears gradually in developing C. elegans embryos and depends on nuclear localization of MET-2. We find that the timing of H3K9me2 and nuclear MET-2 is sensitive to rapid cell cycles, but not to zygotic genome activation or cell counting. These data reveal distinct roles for different H3K9 methylation states in the generation of heterochromatin and loss of developmental plasticity by MET-2, and identify the cell cycle as a crucial parameter of MET-2 regulation.

A modifier in the 129S2/SvPasCrl genome is responsible for the viability of Notch1[12f/12f] mice

Background

Mouse NOTCH1 carries a highly conserved O-fucose glycan at Thr466 in epidermal growth factor-like repeat 12 (EGF12) of the extracellular domain. O-Fucose at this site has been shown by X-ray crystallography to be recognized by both DLL4 and JAG1 Notch ligands. We previously showed that a Notch1 Thr466Ala mutant exhibits very little ligand-induced NOTCH1 signaling in a reporter assay, whereas a Thr466Ser mutation enables the transfer of O-fucose and reverts the NOTCH1 signaling defect. We subsequently generated a mutant mouse with the Thr466Ala mutation termed Notch1[12f](Notch1^tm2Pst). Surprisingly, homozygous Notch1[12f/12f] mutants on a mixed background were viable and fertile.

Results

We now report that after backcrossing to C57BL/6 J mice for 11–15 generations, few homozygous Notch1[12f/12f] embryos were born. Timed mating showed that embryonic lethality occurred by embryonic day (E) ~E11.5, somewhat delayed compared to mice lacking Notch1 or Pofut1 (the O-fucosyltransferase that adds O-fucose to Notch receptors), which die at ~E9.5. The phenotype of C57BL/6 J Notch1[12f/12f] embryos was milder than mutants affected by loss of a canonical Notch pathway member, but disorganized vasculogenesis in the yolk sac, delayed somitogenesis and development were characteristic. In situ hybridization of Notch target genes Uncx4.1 and Dll3 or western blot analysis of NOTCH1 cleavage did not reveal significant differences at E9.5. However, qRT-PCR of head cDNA showed increased expression of Dll3, Uncx4.1 and Notch1 in E9.5 Notch1[12f/12f] embryos. Sequencing of cDNA from Notch1[12f/12f] embryo heads and Southern analysis showed that the Notch1[12f] locus was intact following backcrossing. We therefore looked for evidence of modifying gene(s) by crossing C57BL/6 J Notch1 [12f/+] mice to 129S2/SvPasCrl mice. Intercrosses of the F1 progeny gave viable F2 Notch1[12f/12f] mice.

Conclusion

We conclude that the 129S2/SvPasCrl genome contains a dominant modifying gene that rescues the functions of NOTCH1[12f] in signaling. Identification of the modifying gene has the potential to illuminate novel factor(s) that promote Notch signaling when an O-fucose glycan is absent from EGF12 of NOTCH1.

Perturbed development of cranial neural crest cells in association with reduced sonic hedgehog signaling underlies the pathogenesis of retinoic-acid-induced cleft palate

Cleft palate (CP) is one of the most common congenital craniofacial anomalies in humans and can be caused by either single or multiple genetic and environmental factor(s). With respect to environmental factors, excessive intake of vitamin A during early pregnancy is associated with increased incidence of CP in offspring both in humans and in animal models. Vitamin A is metabolized to retinoic acid (RA); however, the pathogenetic mechanism of CP caused by altered RA signaling during early embryogenesis is not fully understood. To investigate the detailed cellular and molecular mechanism of RA-induced CP, we administered all-trans RA to pregnant mice at embryonic day (E)8.5. In the RA-treated group, we observed altered expression of Sox10, which marks cranial neural crest cells (CNCCs). Disruption of Sox10 expression was also observed at E10.5 in the maxillary component of the first branchial arch, which gives rise to secondary palatal shelves. Moreover, we found significant elevation of CNCC apoptosis in RA-treated embryos. RNA-sequencing comparisons of RA-treated embryos compared to controls revealed alterations in Sonic hedgehog (Shh) signaling. More specifically, the expression of Shh and its downstream genes Ptch1 and Gli1 was spatiotemporally downregulated in the developing face of RA-treated embryos. Consistent with these findings, the incidence of CP in association with excessive RA signaling was reduced by administration of the Shh signaling agonist SAG (Smoothened agonist). Altogether, our results uncovered a novel mechanistic association between RA-induced CP with decreased Shh signaling and elevated CNCC apoptosis.

Germline knockdown of spargel (PGC-1) produces embryonic lethality in Drosophila

The PGC-1 transcriptional coactivators have been proposed as master regulators of mitochondrial biogenesis and energy metabolism. Here we show that the single member of the family in Drosophila, spargel (srl) has an essential role in early development. Female germline-specific RNAi knockdown resulted in embryonic semilethality. Embryos were small, with most suffering a catastrophic derangement of cellularization and gastrulation, although genes dependent on localized determinants were expressed normally. The abundance of mtDNA, representative mitochondrial proteins and mRNAs were not decreased in knockdown ovaries or embryos, indicating that srl has a more general role in early development than specifically promoting mitochondrial biogenesis.

Microarray data on the comparison of transcript expression between normal and Pt-Delta RNAi embryos in the common house spider Parasteatoda tepidariorum

We conducted a custom microarray experiment to detect the differences in the transcript expression levels between untreated (normal) and Pt-Delta-RNAi embryos at late stage 6 in the common house spider Parasteatoda tepidariorum. The array probes were designed based on accumulated EST and cDNA sequences. The microarray dataset has been deposited in the Gene Expression Omnibus (GEO) Database at the National Center for Biotechnology Information (NCBI) under the accession GSE113064. The expression of the transcripts selected based on the detected differences was examined in embryos by whole-mount in situ hybridization.

In Ovo Electroporation of Plasmid DNA and Morpholinos into Specific Tissues During Early Embryogenesis

In ovo electroporation enables transfection of non-viral plasmid DNA and/or morpholinos to fluorescently label and/or perturb gene function in cells of interest. However, targeted electroporation into specific subregions of the embryo can be challenging due to placement and size limitations of the electrodes. Here we describe the basic techniques for in ovo electroporation in the chick embryo and suggest parameters to electroporate cells within different target tissues that with some modifications may be applicable to a wide range of developmental stages and other embryo model organisms.

MEIS transcription factors in development and disease

MEIS transcription factors are key regulators of embryonic development and cancer. Research on MEIS genes in the embryo and in stem cell systems has revealed novel and surprising mechanisms by which these proteins control gene expression. This Primer summarizes recent findings about MEIS protein activity and regulation in development, and discusses new insights into the role of MEIS genes in disease, focusing on the pathogenesis of solid cancers.