ERK5 promotes autocrine expression to sustain mitogenic balance for cell fate specification in human pluripotent stem cells.

The homeostasis of human pluripotent stem cells (hPSCs) requires the signaling balance of extracellular factors. Exogenous regulators from cell culture medium have been widely reported, but little attention has been paid to the autocrine factor from hPSCs themselves. In this report, we demonstrate that extracellular signal-related kinase 5 (ERK5) regulates endogenous autocrine factors essential for pluripotency and differentiation. ERK5 inhibition leads to erroneous cell fate specification in all lineages even under lineage-specific induction. hPSCs can self-renew under ERK5 inhibition in the presence of fibroblast growth factor 2 (FGF2) and transforming growth factor ß (TGF-ß), although NANOG expression is partially suppressed. Further analysis demonstrates that ERK5 promotes the expression of autocrine factors such as NODAL, FGF8, and WNT3. The addition of NODAL protein rescues NANOG expression and differentiation phenotypes under ERK5 inhibition. We demonstrate that constitutively active ERK5 pathway allows self-renewal even without essential growth factors FGF2 and TGF-ß. This study highlights the essential contribution of autocrine pathways to proper maintenance and differentiation.

Overview of chromatin regulatory processes during surface ectodermal development and homeostasis.

The ectoderm is the outermost of the three germ layers of the early embryo that arise during gastrulation. Once the germ layers are established, the complex interplay of cellular proliferation, differentiation, and migration results in organogenesis. The ectoderm is the progenitor of both the surface ectoderm and the neural ectoderm. Notably, the surface ectoderm develops into the epidermis and its associated appendages, nails, external exocrine glands, olfactory epithelium, and the anterior pituitary. Specification, development, and homeostasis of these organs demand a tightly orchestrated gene expression program that is often dictated by epigenetic regulation. In this review, we discuss the recent discoveries that have highlighted the importance of chromatin regulatory mechanisms mediated by transcription factors, histone and DNA modifications that aid in the development of surface ectodermal organs and maintain their homeostasis post-development.

Neural Crest.

This chapter discusses the role of cardiac neural crest cells in the formation of the septum that divides the cardiac arterial pole into separate systemic and pulmonary arteries. Further, cardiac neural crest cells directly support the normal development and patterning of derivatives of the caudal pharyngeal arches, including the great arteries, thymus, thyroid, and parathyroids. Recently, cardiac neural crest cells have also been shown to indirectly influence the development of the secondary heart field, another derivative of the caudal pharynx, by modulating signaling in the pharynx. The contribution and function of the cardiac neural crest cells has been learned in avian models; most of the genes associated with cardiac neural crest function have been identified using mouse models. Together these studies show that the neural crest cells may not only critical for normal cardiovascular development but also may be involved secondarily because they represent a major component in the complex tissue interactions in the caudal pharynx and outflow tract. Cardiac neural crest cells span from the caudal pharynx into the outflow tract, and therefore may be susceptible to any perturbation in or by other cells in these regions. Thus, understanding congenital cardiac outflow malformations in human sequences of malformations resulting from genetic and/or environmental insults necessarily requires better understanding the role of cardiac neural crest cells in cardiac development.

Differential retinoic acid sensitivity of oral and pharyngeal teeth in medaka (Oryzias latipes) supports the importance of pouch-cleft contacts in pharyngeal tooth initiation.

BACKGROUND: Previous studies have claimed that pharyngeal teeth in medaka (Oryzias latipes) are induced independent of retinoic acid (RA) signaling, unlike in zebrafish (Danio rerio). In zebrafish, pharyngeal tooth formation depends on a proper physical contact between the embryonic endodermal pouch anterior to the site of tooth formation, and the adjacent ectodermal cleft, an RA-dependent process. Here, we test the hypothesis that a proper pouch-cleft contact is required for pharyngeal tooth formation in embryonic medaka, as it is in zebrafish. We used 4-[diethylamino]benzaldehyde (DEAB) to pharmacologically inhibit RA production, and thus pouch-cleft contacts, in experiments strictly controlled in time, and analyzed these using high-resolution imaging. RESULTS: Pharyngeal teeth in medaka were present only when the corresponding anterior pouch had reached the ectoderm (i.e., a physical pouch-cleft contact established), similar to the situation in zebrafish. Oral teeth were present even when the treatment started approximately 4 days before normal oral tooth appearance. CONCLUSIONS: RA dependency for pharyngeal tooth formation is not different between zebrafish and medaka. We propose that the differential response to DEAB of oral versus pharyngeal teeth in medaka could be ascribed to the distinct germ layer origin of the epithelia involved in tooth formation in these two regions.

Understanding the effects of per- and polyfluoroalkyl substances on early skin development: Role of ciliogenesis inhibition and altered microtubule dynamics.

Per- and polyfluoroalkyl substances (PFAS) are a class of highly stable chemicals, widely used in everyday products, and widespread in the environment, even in pregnant women. While epidemiological studies have linked prenatal exposure to PFAS with atopic dermatitis in children, little is known about their toxic effects on skin development, especially during the embryonic stage. In this study, we utilized human embryonic stem cells to generate non-neural ectoderm (NNE) cells and exposed them to six PFAS (perfluorooctanoic acid (PFOA), undecafluorohexanoic acid (PFHxA), heptafluorobutyric acid (PFBA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) and perfluorobutyric acid (PFBS)) during the differentiation process to assess their toxicity to early skin development. Our results showed that PFOS altered the spindle-like morphology of NNE cells to a pebble-like morphology, and disrupted several NNE markers, including KRT16, SMYD1, and WISP1. The six PFAS had a high potential to cause hypohidrotic ectodermal dysplasia (HED) by disrupting the expression levels of HED-relevant genes. Transcriptomic analysis revealed that PFOS treatment produced the highest number (1156) of differentially expressed genes (DEGs) among the six PFAS, including the keratinocyte-related genes KRT6A, KRT17, KRT18, KRT24, KRT40, and KRT81. Additionally, we found that PFOS treatment disturbed several signaling pathways that are involved in regulating skin cell fate decisions and differentiation, including TGF-ß, NOTCH, Hedgehog, and Hippo signaling pathways. Interestingly, we discovered that PFOS inhibited, by partially interfering with the expression of cytoskeleton-related genes, the ciliogenesis of NNE cells, which is crucial for the intercellular transduction of the above-mentioned signaling pathways. Overall, our study suggests that PFAS can inhibit ciliogenesis and hamper the transduction of important signaling pathways, leading potential congenital skin diseases. It sheds light on the underlying mechanisms of early embryonic skin developmental toxicity and provides an explanation for the epidemiological data on PFAS. ENVIRONMENTAL IMPLICATION: We employed a model based on human embryonic stem cells to demonstrate that PFOS has the potential to elevate the risk of hypohidrotic ectodermal dysplasia. This is achieved by targeting cilia, inhibiting ciliogenesis, and subsequently disrupting crucial signaling pathways like TGF-ß, NOTCH, Hedgehog, and Hippo, during the early phases of embryonic skin development. Our study highlights the dangers and potential impacts of six PFAS pollutants on human skin development. Additionally, we emphasize the importance of closely considering PFHxA, PFBA, PFHxS, and PFBS, as they have shown the capacity to modify gene expression levels, albeit to a lesser degree.

[Exosomes from ectoderm mesenchymal stem cells inhibits lipopolysaccharide-induced microglial M1 polarization and promotes survival of H2O2-exposed PC12 cells by suppressing inflammatory response and oxidative stress].

OBJECTIVE: To investigate the potential value of exosomes derived from rat ectoderm mesenchymal stem cells (EMSCs-exo) for repairing secondary spinal cord injury. METHODS: EMSCs-exo were obtained using ultracentrifugation from EMSCs isolated from rat nasal mucosa, identified by transmission electron microscope, nanoparticle tracking analysis (NTA), and Western blotting, and quantified using the BCA method. Neonatal rat microglia purified by differential attachment were induced with 100 µg/L lipopolysaccharide (LPS) and treated with 37.5 or 75 mg/L EMSCs-exo. PC12 cells were exposed to 400 µmol/L H2O2 and treated with EMSCs-exo at 37.5 or 75 mg/L. The protein and mRNA expressions of Arg1 and iNOS in the treated cells were determined with Western blotting and qRT- PCR, and the concentrations of IL- 6, IL-10, and IGF-1 in the supernatants were measured with ELISA. The viability and apoptosis of PC12 cells were detected using CCK-8 assay and flow cytometry. RESULTS: The isolated rat EMSCs showed high expressions of nestin, CD44, CD105, and vimentin. The obtained EMSCs-exo had a typical cup-shaped structure under transmission electron microscope with an average particle size of 142 nm and positivity for CD63, CD81, and TSG101 but not vimentin. In LPS-treated microglia, EMSCs-exo treatment at 75 mg/L significantly increased Arg1 protein level and lowered iNOS protein expression (P < 0.05). EMSCs-exo treatment at 75 mg/L, as compared with the lower concentration at 37.5 mg/L, more strongly increased Arg1 mRNA expression and IGF-1 and IL-10 production and decreased iNOS mRNA expression and IL-6 production in LPS-induced microglia, and more effectively promoted cell survival and decreased apoptosis rate of H2O2-induced PC12 cells (P < 0.05). CONCLUSION: EMSCs-exo at 75 mg/L can effectively reduce the proportion of M1 microglia and alleviate neuronal apoptosis under oxidative stress to promote neuronal survival, suggesting its potential in controlling secondary spinal cord injury.

Bop1 is required to establish precursor domains of craniofacial tissues.

Bop1 can promote cell proliferation and is a component of the Pes1-Bop1-WDR12 (PeBoW) complex that regulates ribosomal RNA processing and biogenesis. In embryos, however, bop1 mRNA is highly enriched in the neural plate, cranial neural crest and placodes, and potentially may interact with Six1, which also is expressed in these tissues. Recent work demonstrated that during development, Bop1 is required for establishing the size of the tadpole brain, retina and cranial cartilages, as well as controlling neural tissue gene expression levels. Herein, we extend this work by assessing the effects of Bop1 knockdown at neural plate and larval stages. Loss of Bop1 expanded neural plate gene expression domains (sox2, sox11, irx1) and reduced neural crest (foxd3, sox9), placode (six1, sox11, irx1, sox9) and epidermal (dlx5) expression domains. At larval stages, Bop1 knockdown reduced the expression of several otic vesicle genes (six1, pax2, irx1, sox9, dlx5, otx2, tbx1) and branchial arch genes that are required for chondrogenesis (sox9, tbx1, dlx5). The latter was not the result of impaired neural crest migration. Together these observations indicate that Bop1 is a multifunctional protein that in addition to its well-known role in ribosomal biogenesis functions during early development to establish the craniofacial precursor domains.

Fgf signalling is required for gill slit formation in the skate, Leucoraja erinacea.

The gill slits of fishes develop from an iterative series of pharyngeal endodermal pouches that contact and fuse with surface ectoderm on either side of the embryonic head. We find in the skate (Leucoraja erinacea) that all gill slits form via a stereotypical sequence of epithelial interactions: 1) endodermal pouches approach overlying surface ectoderm, with 2) focal degradation of ectodermal basement membranes preceding endoderm-ectoderm contact; 3) endodermal pouches contact and intercalate with overlying surface ectoderm, and finally 4) perforation of a gill slit occurs by epithelial remodelling, without programmed cell death, at the site of endoderm-ectoderm intercalation. Skate embryos express Fgf8 and Fgf3 within developing pharyngeal epithelia during gill slit formation. When we inhibit Fgf signalling by treating skate embryos with the Fgf receptor inhibitor SU5402 we find that endodermal pouch formation, basement membrane degradation and endodermal-ectodermal intercalation are unaffected, but that epithelial remodelling and gill slit perforation fail to occur. These findings point to a role for Fgf signalling in epithelial remodelling during gill slit formation in the skate and, more broadly, to an ancestral role for Fgf signalling during pharyngeal pouch epithelial morphogenesis in vertebrate embryos.

Epidermoid cyst in the right mandible: a case report and literature review / 口腔疾病防治

Objective@#To discuss the possible etiology, pathogenesis, clinical features, diagnosis and treatment of epidermoid cysts of the jaw and to provide a reference for clinical diagnosis and treatment.@*Methods@#A case of an epidermoid cyst in the right mandible with retained deciduous teeth and succedaneous impacted teeth was reviewed and analyzed in combination with the relevant literature.@*Results@#A patient presented with a mass in the right mandible that had persisted for 1 month after being found at imaging examination. Tooth 83 was retained, and tooth 43 was unerupted. Swelling was characterized by no obvious tenderness, fluctuation, or table tennis sensation and was observed in the lingual alveoli of teeth 83, 44, and 45. Imaging revealed a low-density shadow in the apex of teeth 83, 44, 45, and 46, approximately 1.9 cm × 2.6 cm × 1.6 cm in size, which wrapped around the dental crown of tooth 43. Preliminary diagnoses were as follows: right mandibular mass thought to be a dentigerous cyst; impacted tooth 43; and retained primary tooth 83. The mass in the right mandible was removed, and teeth 43 and 83 were extracted under intravenous and inhalation anesthesia. During the operation, the mass was observed to have a thin cyst wall and contained bean-like residue. Histopathological examination indicated an epidermoid cyst in the right mandible. At the 1-week follow-up examination, the patient reported no discomfort, and the surgical area showed good recovery. According to the literature, epidermoid cysts are benign cysts originating from ectopic ectodermal tissue that can occur throughout the body but rarely in the oral cavity and are even extremely rarer in the jaw. Epidermoid cysts of the jaw, which have no specific clinical manifestations, can be confused with odontogenic cysts such as dentigerous cysts and odontogenic tumors. Dental pulp tests and other techniques can serve as a reference for clinicians. The diagnosis is confirmed via histopathology. Surgical removal is a common treatment, with a good prognosis and a low recurrence rate.@*Conclusion@#The principle of treatment for an epidermoid cyst of the jaw is similar to that for a jaw cyst. The prognosis is good when the cyst is removed completely.

Transcriptional differential analysis of ocular surface ectoderm and surface ectoderm / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To identify transcriptional differences between the ocular surface ectoderm(OSE)and surface ectoderm(SE)using RNA-seq, and elucidate the OSE transcriptome landscape and the regulatory networks involved in its development.METHODS:OSE and SE cells were differentiated from human embryonic stem(hES)cells. Differentially expressed genes(DEGs)between OSE and SE were analyzed using RNA-seq. Based on the DEGs, we performed gene ontology(GO)analysis, Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway enrichment analysis, and protein-protein interaction(PPI)network analysis. Transcription factors(TFs)and hub genes were screened. Subsequently, TF-gene and TF-miRNA regulatory networks were constructed using the NetworkAnalyst platform.RESULTS:A total of 4 182 DEGs were detected between OSE and SE cells, with 2 771 up-regulated and 1 411 down-regulated genes in OSE cells. GO-BP analysis revealed that up-regulated genes in OSE were enriched in the regulation of ion transmembrane transport, axon development, and modulation of chemical synaptic transmission. Down-regulated genes were primarily involved in nuclear division, chromosome segregation, and regulation of cell cycle phase transition. KEGG analysis indicated that up-regulated genes in OSE cells were enriched in signaling pathways such as cocaine addiction, axon guidance, and amphetamine addiction, while down-regulated genes were enriched in proteoglycans in cancer, ECM-receptor interaction, protein digestion and absorption, and cytokine-cytokine receptor interaction. Additionally, compared with SE, 204 TFs(including FOS, EGR1, POU5F1, SOX2, and PAX6)were up-regulated, and 80 TFs(including HAND2, HOXB6, HOXB5, HOXA5, and HOXB8)were down-regulated in OSE cells. Furthermore, we identified 6 up-regulated and 9 down-regulated hub genes in OSE cells, and constructed TF-gene and TF-miRNA regulatory networks based on these hub genes.CONCLUSIONS:The transcriptome characteristics of OSE and SE cells were elucidated through RNA-seq analysis. These findings may provide a novel insight for studies on the development and in vitro directed induction of OSE and corneal epithelial cells.

Claudin-3 in the non-neural ectoderm is essential for neural fold fusion in chicken embryos.

The neural tube, the embryonic precursor to the brain and spinal cord, begins as a flat sheet of epithelial cells, divided into non-neural and neural ectoderm. Proper neural tube closure requires that the edges of the neural ectoderm, the neural folds, to elevate upwards and fuse along the dorsal midline of the embryo. We have previously shown that members of the claudin protein family are required for the early phases of chick neural tube closure. Claudins are transmembrane proteins, localized in apical tight junctions within epithelial cells where they are essential for regulation of paracellular permeability, strongly involved in apical-basal polarity, cell-cell adhesion, and bridging the tight junction to cytoplasmic proteins. Here we explored the role of Claudin-3 (Cldn3), which is specifically expressed in the non-neural ectoderm. We discovered that depletion of Cldn3 causes folic acid-insensitive primarily spinal neural tube defects due to a failure in neural fold fusion. Apical cell surface morphology of Cldn3-depleted non-neural ectodermal cells exhibited increased membrane blebbing and smaller apical surfaces. Although apical-basal polarity was retained, we observed altered Par3 and Pals1 protein localization patterns within the apical domain of the non-neural ectodermal cells in Cldn3-depleted embryos. Furthermore, F-actin signal was reduced at apical junctions. Our data presents a model of spina bifida, and the role that Cldn3 is playing in regulating essential apical cell processes in the non-neural ectoderm required for neural fold fusion.

Roles of the Rlim-Rex1 axis during X chromosome inactivation in mice.

In female mice, the gene dosage from X chromosomes is adjusted by a process called X chromosome inactivation (XCI) that occurs in two steps. An imprinted form of XCI (iXCI) that silences the paternally inherited X chromosome (Xp) is initiated at the 2- to 4-cell stages. As extraembryonic cells including trophoblasts keep the Xp silenced, epiblast cells that give rise to the embryo proper reactivate the Xp and undergo a random form of XCI (rXCI) around implantation. Both iXCI and rXCI require the lncRNA Xist, which is expressed from the X to be inactivated. The X-linked E3 ubiquitin ligase Rlim (Rnf12) in conjunction with its target protein Rex1 (Zfp42), a critical repressor of Xist, have emerged as major regulators of iXCI. However, their roles in rXCI remain controversial. Investigating early mouse development, we show that the Rlim-Rex1 axis is active in pre-implantation embryos. Upon implantation Rex1 levels are downregulated independently of Rlim specifically in epiblast cells. These results provide a conceptual framework of how the functional dynamics between Rlim and Rex1 ensures regulation of iXCI but not rXCI in female mice.

Signalling pathway crosstalk stimulated by L-proline drives mouse embryonic stem cells to primitive-ectoderm-like cells.

The amino acid L-proline exhibits growth factor-like properties during development - from improving blastocyst development to driving neurogenesis in vitro. Addition of 400 µM L-proline to self-renewal medium drives naïve mouse embryonic stem cells (ESCs) to early primitive ectoderm-like (EPL) cells - a transcriptionally distinct primed or partially primed pluripotent state. EPL cells retain expression of pluripotency genes, upregulate primitive ectoderm markers, undergo a morphological change and have increased cell number. These changes are facilitated by a complex signalling network hinging on the Mapk, Fgfr, Pi3k and mTor pathways. Here, we use a factorial experimental design coupled with statistical modelling to understand which signalling pathways are involved in the transition between ESCs and EPL cells, and how they underpin changes in morphology, cell number, apoptosis, proliferation and gene expression. This approach reveals pathways which work antagonistically or synergistically. Most properties were affected by more than one inhibitor, and each inhibitor blocked specific aspects of the naïve-to-primed transition. These mechanisms underpin progression of stem cells across the in vitro pluripotency continuum and serve as a model for pre-, peri- and post-implantation embryogenesis.

Prechordal structures act cooperatively in early trabeculae development of gnathostome skull.

The vertebrate skull is formed by mesoderm and neural crest (NC) cells. The mesoderm contributes to the skull chordal domain, with the notochord playing an essential role in this process. The NC contributes to the skull prechordal domain, prompting investigation into the embryonic structures involved in prechordal neurocranium cartilage formation. The trabeculae cartilage, a structure of the prechordal neurocranium, arises at the convergence of prechordal plate (PCP), ventral midline (VM) cells of the diencephalon, and dorsal oral ectoderm. This study examines the molecular participation of these embryonic structures in gnathostome trabeculae development. PCP-secreted SHH induces its expression in VM cells of the diencephalon, initiating a positive feedback loop involving SIX3 and GLI1. SHH secreted by the VM cells of the diencephalon acts on the dorsal oral ectoderm, stimulating condensation of NC cells to form trabeculae. SHH from the prechordal region affects the expression of SOX9 in NC cells. BMP7 and SHH secreted by PCP induce NKX2.1 expression in VM cells of the diencephalon, but this does not impact trabeculae formation. Molecular cooperation between PCP, VM cells of the diencephalon, and dorsal oral ectoderm is crucial for craniofacial development by NC cells in the prechordal domain.

Zmym4 is required for early cranial gene expression and craniofacial cartilage formation.

Introduction: The Six1 transcription factor plays important roles in the development of cranial sensory organs, and point mutations underlie craniofacial birth defects. Because Six1's transcriptional activity can be modulated by interacting proteins, we previously screened for candidate interactors and identified zinc-finger MYM-containing protein 4 (Zmym4) by its inclusion of a few domains with a bona fide cofactor, Sine oculis binding protein (Sobp). Although Zmym4 has been implicated in regulating early brain development and certain cancers, its role in craniofacial development has not previously been described. Methods: We used co-immunoprecipitation and luciferase-reporter assays in cultured cells to test interactions between Zmym4 and Six1. We used knock-down and overexpression of Zmym4 in embryos to test for its effects on early ectodermal gene expression, neural crest migration and craniofacial cartilage formation. Results: We found no evidence that Zmym4 physically or transcriptionally interacts with Six1 in cultured cells. Nonetheless, knockdown of endogenous Zmym4 in embryos resulted in altered early cranial gene expression, including those expressed in the neural border, neural plate, neural crest and preplacodal ectoderm. Experimentally increasing Zmym4 levels had minor effects on neural border or neural plate genes, but altered the expression of neural crest and preplacodal genes. At larval stages, genes expressed in the otic vesicle and branchial arches showed reduced expression in Zmym4 morphants. Although we did not detect defects in neural crest migration into the branchial arches, loss of Zmym4 resulted in aberrant morphology of several craniofacial cartilages. Discussion: Although Zmym4 does not appear to function as a Six1 transcriptional cofactor, it plays an important role in regulating the expression of embryonic cranial genes in tissues critical for normal craniofacial development.

Gastrulation and Split Cord Malformation.

Split cord malformation (SCM) is a rare form of closed spinal dysraphism, in which two hemi-cords are present, instead of a single spinal cord. SCM is categorised into type 1 and type 2. Type 1 SCM is defined by the presence of a bony or osseocartilaginous spur between the hemi-cords, whereas type 2 SCM has no bony spur, and the two hemi-cords are contained within a single dura. In this chapter, we present the putative mechanisms by which SCM arises, including gastrulation defects and Pang's unified theory. The typical and rare clinical presentations and variations are described. Finally, we outline the step-by-step surgical approach to both SCM 1 and 2 and the overall prognosis of both conditions.

The sulfotransferase XB5850668.L is required to apportion embryonic ectodermal domains.

BACKGROUND: Members of the sulfotransferase superfamily (SULT) influence the activity of a wide range of hormones, neurotransmitters, metabolites and xenobiotics. However, their roles in developmental processes are not well characterized even though they are expressed during embryogenesis. We previously found in a microarray screen that Six1 up-regulates LOC100037047, which encodes XB5850668.L, an uncharacterized sulfotransferase. RESULTS: Since Six1 is required for patterning the embryonic ectoderm into its neural plate, neural crest, preplacodal and epidermal domains, we used loss- and gain-of function assays to characterize the role of XB5850668.L during this process. Knockdown of endogenous XB5850668.L resulted in the reduction of epidermal, neural crest, cranial placode and otic vesicle gene expression domains, concomitant with neural plate expansion. Increased levels had minimal effects, but infrequently expanded neural plate and neural crest gene domains, and infrequently reduced cranial placode and otic vesicle gene domains. Mutation of two key amino acids in the sulfotransferase catalytic domain required for PAPS binding and enzymatic activity tended to reduce the effects of overexpressing the wild-type protein. CONCLUSIONS: Our analyses indicates that XB5850668.L is a member of the SULT2 family that plays important roles in patterning the embryonic ectoderm. Some aspects of its influence likely depend on sulfotransferase activity.

Derivation and characteristics of induced pluripotent stem cells from a patient with acute myelitis.

The emergence and development of induced pluripotent stem cells (iPSCs) provides an approach to understand the regulatory mechanisms of cell pluripotency and demonstrates the great potential of iPSCs in disease modeling. Acute myelitis defines a group of inflammatory diseases that cause acute nerve damage in the spinal cord; however, its pathophysiology remains to be elusive. In this study, we derived skin fibroblasts from a patient with acute myelitis (P-HAF) and then reprogrammed P-HAF cells to iPSCs using eight exogenous factors (namely, OCT4, SOX2, c-MYC, KLF4, NANOG, LIN28, RARG, and LRH1). We performed transcriptomic analysis of the P-HAF and compared the biological characteristics of the iPSCs derived from the patient (P-iPSCs) with those derived from normal individuals in terms of pluripotency, transcriptomic characteristics, and differentiation ability toward the ectoderm. Compared to the control iPSCs, the P-iPSCs displayed similar features of pluripotency and comparable capability of ectoderm differentiation in the specified culture. However, when tested in the common medium, the P-iPSCs showed attenuated potential for ectoderm differentiation. The transcriptomic analysis revealed that pathways enriched in P-iPSCs included those involved in Wnt signaling. To this end, we treated iPSCs and P-iPSCs with the Wnt signaling pathway inhibitor IWR1 during the differentiation process and found that the expression of the ectoderm marker Sox1 was increased significantly in P-iPSCs. This study provides a novel approach to investigating the pathogenesis of acute myelitis.

The surface ectoderm exhibits spatially heterogenous tension that correlates with YAP localisation during spinal neural tube closure in mouse embryos.

The single cell layer of surface ectoderm (SE) which overlies the closing neural tube (NT) plays a crucial biomechanical role during mammalian NT closure (NTC), challenging previous assumptions that it is only passive to the force-generating neuroepithelium (NE). Failure of NTC leads to congenital malformations known as NT defects (NTDs), including spina bifida (SB) and anencephaly in the spine and brain respectively. In several mouse NTD models, SB is caused by misexpression of SE-specific genes and is associated with disrupted SE mechanics, including loss of rostrocaudal cell elongation believed to be important for successful closure. In this study, we asked how SE mechanics affect NT morphology, and whether the characteristic rostrocaudal cell elongation at the progressing closure site is a response to tension anisotropy in the SE. We show that blocking SE-specific E-cadherin in ex utero mouse embryo culture influences NT morphology, as well as the F-actin cable. Cell border ablation shows that cell shape is not due to tension anisotropy, but that there are regional differences in SE tension. We also find that YAP nuclear translocation reflects regional tension heterogeneity, and that its expression is sensitive to pharmacological reduction of tension. In conclusion, our results confirm that the SE is a biomechanically important tissue for spinal NT morphogenesis and suggest a possible role of spatial regulation of cellular tension which could regulate downstream gene expression via mechanically-sensitive YAP activity.

H3K27me3-H3K4me1 transition at bivalent promoters instructs lineage specification in development.

BACKGROUND: Bivalent genes, of which promoters are marked by both H3K4me3 (trimethylation of histone H3 on lysine 4) and H3K27me3 (trimethylation of histone H3 on lysine 27), play critical roles in development and tumorigenesis. Monomethylation on lysine 4 of histone H3 (H3K4me1) is commonly associated with enhancers, but H3K4me1 is also present at promoter regions as an active bimodal or a repressed unimodal pattern. Whether the co-occurrence of H3K4me1 and bivalent marks at promoters plays regulatory role in development is largely unknown. RESULTS: We report that in the process of lineage differentiation, bivalent promoters undergo H3K27me3-H3K4me1 transition, the loss of H3K27me3 accompanies by bimodal pattern loss or unimodal pattern enrichment of H3K4me1. More importantly, this transition regulates tissue-specific gene expression to orchestrate the development. Furthermore, knockout of Eed (Embryonic Ectoderm Development) or Suz12 (Suppressor of Zeste 12) in mESCs (mouse embryonic stem cells), the core components of Polycomb repressive complex 2 (PRC2) which catalyzes H3K27 trimethylation, generates an artificial H3K27me3-H3K4me1 transition at partial bivalent promoters, which leads to up-regulation of meso-endoderm related genes and down-regulation of ectoderm related genes, thus could explain the observed neural ectoderm differentiation failure upon retinoic acid (RA) induction. Finally, we find that lysine-specific demethylase 1 (LSD1) interacts with PRC2 and contributes to the H3K27me3-H3K4me1 transition in mESCs. CONCLUSIONS: These findings suggest that H3K27me3-H3K4me1 transition plays a key role in lineage differentiation by regulating the expression of tissue specific genes, and H3K4me1 pattern in bivalent promoters could be modulated by LSD1 via interacting with PRC2.