Crest Formation Research Articles

Short-term perinatal oxygen exposure may impair lung development in adult mice

BackgroundHyperoxia at resuscitation increases oxidative stress, and even brief exposure to high oxygen concentrations during stabilization may trigger organ injury with adverse long-term outcomes in premature infants. We studied the long-term effects of short-term perinatal oxygen exposure on cell cycle gene expression and lung growth in adult mice.MethodsWe randomized mice litters at birth to 21, 40, or 100%O2 for 30 min and recovered in room air for 4 or 12 weeks. Cell cycle gene expression, protein analysis, and lung morphometry were assessed at 4 and 12 weeks.ResultsThe principal component analysis demonstrated a high degree of correlation for cell cycle gene expression among the three oxygen groups. Lung elastin was significantly lower in the 100%O2 groups at 4 weeks. On lung morphometry, radial alveolar count, alveolar number, and septal count were similar. However, the mean linear intercept (MLI) and septal length significantly correlated among the oxygen groups. The MLI was markedly higher in the 100%O2 groups at 4 and 12 weeks of age, and the septal length was significantly lower in the 100%O2 groups at 12 weeks.ConclusionShort-term exposure to high oxygen concentrations lead to subtle changes in lung development that may affect alveolarization. The changes are related explicitly to secondary crest formation that may result in alteration in lung elastin. Resuscitation with high oxygen concentrations may have a significant impact on lung development and long-term outcomes such as BPD in premature infants.

PR domaincontaining protein 12 (prdm12) is a downstream target of the transcription factor zic1 during cellular differentiation in the central nervous system: PR domain containing protein is the right form.

Transcription factor zic1 is an important regulator of neural plate patterning, formation of neural crest and cerebellar development, where its main function is neuronal cell differentiation. Among the genes identified, PR domain-containing 12 (prdm12) is a member of the prdm family and is expressed in the placode domain in the neurula stage. prdm12 is distinctly expressed in the dorsal part of the midbrain, trigeminal ganglion, and the motor neuron in the spinal cord. prdm12 knockdown results in the ventralization of the neural tube. zic1 knockdown results in the reduction of prdm12 expression in the midbrain, motor neuron and trigeminal ganglion, and overexpression of zic1 results in the expansion of prdm12 expression in the midbrain. zic1-activated wnt signaling is also a regulator of prdm12 expression in the midbrain. We propose that prdm12 is the downstream of zic1 and a novel player in the gene regulatory network controlling brain cell differentiation, along with some ganglions in Xenopus.

Mathematical modelling of the process of crest formation by the working body of the cultivator – dump type

The results of theoretical studies of the cultivator - dump type ridger are presented. The analysis of the forces acting on the working body is carried out. An expression is obtained for determining the second consumption of soil mass transported by a working body. The rational parameters of the working body are determined.

Recapitulation of Neural Crest Specification and EMT via Induction from Neural Plate Border-like Cells

SummaryNeural crest cells (NCCs) contribute to several tissues during embryonic development. NCC formation depends on activation of tightly regulated molecular programs at the neural plate border (NPB) region, which initiate NCC specification and epithelial-to-mesenchymal transition (EMT). Although several approaches to investigate NCCs have been devised, these early events of NCC formation remain largely unknown in humans, and currently available cellular models have not investigated EMT. Here, we report that the E6 neural induction protocol converts human induced pluripotent stem cells into NPB-like cells (NBCs), from which NCCs can be efficiently derived. NBC-to-NCC induction recapitulates gene expression dynamics associated with NCC specification and EMT, including downregulation of NPB factors and upregulation of NCC specifiers, coupled with other EMT-associated cell-state changes, such as cadherin modulation and activation of TWIST1 and other EMT inducers. This strategy will be useful in future basic or translational research focusing on these early steps of NCC formation.

Function study of vasoactive intestinal peptide on chick embryonic bone development

Embryonic bone development is a complicated procedure and modulated by neuro-osteogenic interaction. Vasoactive intestinal peptide (VIP) was first identified as a neural vasodilator and further proved to possess multiple biological functions such as neurotransmitter and immune regulator. However, as a key peptide regulator presented in skeletal nerve fibers, the function of VIP on innervation and early bone development regulation has not fully been uncovered yet. In this study, the chick embryo has been used as an experimental model to address the effect of VIP on embryonic bone development. Our study results confirmed the innervation of peripheral nerve fibers into limb bone tissue, which was revealed by the detection of neurofilament (NF) and class III β-tubulin (TUJ-1) in bone tissue at various developing stages. The VIP mRNA and peptide expression level in bone tissue were also increased upon innervation progress. A chick embryonic chemical sympathectomy model was constructed by exposing chick embryos with neurotoxin 6-OHDA. The 6-OHDA exposure of the early chick embryo caused the reduction of neural crest formation and NF expression. 6-OHDA treatment also inhibited distal limb bone development as well as VIP expression. Furthermore, co-application of VIP with 6-OHDA exposure could rescue the inhibited osteogenesis activity and delayed bone development during embryogenesis. Taken together, these results reveal that VIP played an important role during innervation at early stage of bone development. VIP could restore chemical sympathectomy induced osteogenesis inhibition and bone development impair in chick embryos.

Intracellular Enhancement of BMP Signaling by LIM-Domain Protein FHL3 Controls Spatiotemporal Emergence of the Neural Crest Driven by WNT Signaling

How multiple morphogens are coordinated in space and time to position key embryonic tissues remains elusive. During neural crest formation, bone morphogenetic protein (BMP), fibroblast growth factor (FGF) and WNT signaling cooperate by acting either on the paraxial mesoderm or directly on the neural border ectoderm, but how each tissue interprets this complex information remains poorly understood. Here we show that Fhl3, a scaffold LIM domain protein of previously unknown developmental function, is essential for neural crest formation by linking BMP and WNT signaling thereby positioning the neural crest-inducing signaling center in the paraxial mesoderm. During gastrulation, Fhl3 promotes Smad phosphorylation and Smad-dependent wnt8 activation in the paraxial mesoderm, thus enhancing the response of mesoderm compared to ectoderm although both germ layers are subjected to a common extracellular BMP gradient. This promotes a non-cell autonomous WNT signaling ensuring neural border ectoderm specification by the underlying mesoderm. During neurulation, in turn, neural crest inducers activate fhl3 in the ectoderm, promoting BMP/Smad-dependent WNT activity required for neural crest specification. We show that Fhl3 binds Smads downstream of BMP signals and promotes Smad binding to wnt8 regulatory elements. Our findings highlight how Fhl3, acting cell-autonomously, ensures a fine spatial and temporal coordination of BMP and WNT signaling at several steps of neural crest development.

Median Nail Dystrophy of both Thumbs

Heller’s medial canaliform dystrophy (MCD) is a rare entity characterized by the paramedian crest formation of one or both thumbnails [1]. We report a case of a 13-year-old child who was used to biting thumbnails during several stressful events and diagnosed as medial ductal dystrophy of the thumbnail.

Neural Functions Play Different Roles in Triple Negative Breast Cancer (TNBC) and non-TNBC

Triple negative breast cancer (TNBC) represents the most malignant subtype of breast cancer, and yet our understanding about its unique biology remains elusive. We have conducted a comparative computational analysis of transcriptomic data of TNBC and non-TNBC (NTNBC) tissue samples from the TCGA database, focused on genes involved in neural functions. Our main discoveries are: (1) while both subtypes involve neural functions, TNBC has substantially more up-regulated neural genes than NTNBC, suggesting that TNBC is more complex than NTNBC; (2) non-neural functions related to cell-microenvironment interactions and intracellular damage processing are key inducers of the neural genes in both TNBC and NTNBC, but the inducer-responder relationships are different in the two cancer subtypes; (3) key neural functions such as neural crest formation are predicted to enhance adaptive immunity in TNBC while glia development, along with a few other neural functions, induce both innate and adaptive immunity in NTNBC. These results reveal key differences in the biology between the two cancer subtypes, particularly in terms of the roles that neural functions play. Our findings may open new doors for further investigation of the distinct biology of TNBC vs. NTNBC.

Reprogramming of chimpanzee fibroblasts into a multipotent cancerous but not fully pluripotent state by transducing iPSC factors in 2i/LIF culture

To induce and maintain naïve pluripotency in mouse embryonic and induced pluripotent stem cells (ESCs/iPSCs), chemically defined N2B27 medium with PD0325901, CHIR99021, and leukemia inhibitory factor (2i/LIF) is a classic and simple condition. However, this method cannot be simply extrapolated to human ESCs/iPSCs that are principally stabilized in primed pluripotency and become primitive neuroepithelium-like cells in N2B27+2i/LIF culture. Here, we assessed iPSC reprogramming of fibroblasts from chimpanzee, our closest living relative, in N2B27+2i/LIF culture. Under this condition, chimpanzee cells formed alkaline phosphatase-positive dome-shaped colonies. The colony-forming cells could be stably expanded by serial passaging without a ROCK inhibitor. However, their gene expression was distinct from iPSCs and neuroepithelium. They expressed the OCT3/4 transgene and a subset of transcripts associated with pluripotency, mesenchymal-epithelial transition, and neural crest formation. These cells exhibited a differentiation potential into the three germ layers in vivo and in vitro. The current study demonstrated that iPSC reprogramming in N2B27+2i/LIF culture converted chimpanzee fibroblasts into a multipotent cancerous state with unique gene expression, but not fully pluripotent stem cells.

Post-transcriptional regulation of BRG1 by FIR\u0394exon2 in gastric cancer

Brahma-related gene 1 (BRG1), an ATPase subunit of the SWItch/sucrose non-fermentable (SWI/SNF) chromatin remodeling complex controls multipotent neural crest formation by regulating epithelial-mesenchymal transition (EMT)-related genes with adenosine triphosphate-dependent chromodomain-helicase DNA-binding protein 7 (CHD7). The expression of BRG1 engages in pre-mRNA splicing through interacting RNPs in cancers; however, the detailed molecular pathology of how BRG1and CHD7 relate to cancer development remains largely unveiled. This study demonstrated novel post-transcriptional regulation of BRG1 in EMT and relationship with FIRΔexon2, which is a splicing variant of the far-upstream element-binding protein (FUBP) 1-interacting repressor (FIR) lacking exon 2, which fails to repress c-myc transcription in cancers. Previously, we have reported that FIR complete knockout mice (FIR−/−) was embryonic lethal before E9.5, suggesting FIR is crucial for development. FIRΔexon2 acetylated H3K27 on promoter of BRG1 by CHIP-sequence and suppressed BRG1 expression post-transcriptionally; herein BRG1 suppressed Snai1 that is a transcriptional suppressor of E-cadherin that prevents cancer invasion and metastasis. Ribosomal proteins, hnRNPs, splicing-related factors, poly (A) binding proteins, mRNA-binding proteins, tRNA, DEAD box, and WD-repeat proteins were identified as co-immunoprecipitated proteins with FIR and FIRΔexon2 by redoing exhaustive mass spectrometry analysis. Furthermore, the effect of FIRΔexon2 on FGF8 mRNA splicing was examined as an indicator of neural development due to impaired CHD7 revealed in CHARGE syndrome. Expectedly, siRNA of FIRΔexon2 altered FGF8 pre-mRNA splicing, indicated close molecular interaction among FIRΔexon2, BRG1 and CHD7. FIRΔexon2 mRNA was elevated in human gastric cancers but not in non-invasive gastric tumors in FIR+/ mice (K19-Wnt1/C2mE x FIR+/−). The levels of FIR family (FIR, FIRΔexon2 and PUF60), BRG1, Snai1, FBW7, E-cadherin, c-Myc, cyclin-E, and SAP155 increased in the gastric tumors in FIR+/− mice compared to those expressed in wild-type mice. FIR family, Snai1, cyclin-E, BRG1, and c-Myc showed trends toward higher expression in larger tumors than in smaller tumors in Gan-mice (K19-Wnt1/C2mE). The expressions of BRG1 and Snai1 were positively correlated in the gastric tumors of the Gan-mice. Finally, BRG1 is a candidate substrate of F-box and WD-repeat domain-containing 7 (FBW7) revealed by three-dimensional crystal structure analysis that the U2AF-homology motif (UHM) of FIRΔexon2 interacted with tryptophan-425 and asparate-399 (WD)-like motif in the degron pocket of FBW7 as a UHM-ligand motif. Together, FIRΔexon2 engages in multi-step post-transcriptional regulation of BRG1, affecting EMT through the BRG1/Snai1/E-cadherin pathway and promoting tumor proliferation and invasion of gastric cancers.

A Hox gene regulatory network for hindbrain segmentation.

In vertebrates, the hindbrain serves as a highly conserved complex coordination center for regulating many fundamental activities of the central nervous system, such as respiratory rhythms, sleep patterns and equilibrium, and it also plays an important role in craniofacial development. The basic ground plan that underlies the diverse functions of the hindbrain and its neural crest derivatives is established and patterned by a process of segmentation. Through a dynamic series of signaling and regulatory interactions the developing hindbrain is transiently compartmentalized into a set of seven segmental units, termed rhombomeres. The nested expression of the Hox family of transcription factors is tightly coupled to the process of segmentation and provides a molecular code for specifying the unique regional properties of the hindbrain and its neural crest derived craniofacial structures. The high degree of similarity in hindbrain architecture between diverse vertebrates has enabled cross-species regulatory analysis. This has facilitated the experimental assembly of the signaling and regulatory interactions, which underlie the process of segmentation, into a Hox-dependent gene regulatory network (GRN) model. This hindbrain GRN is a key regulatory feature of head patterning, conserved to the base of vertebrate evolution. This regulatory framework also serves as a basis for comparing and contrasting GRNs that govern cranial neural crest formation and axial patterning and provide insight into regulatory mechanisms associated with the evolution of novel vertebrate traits. The purpose of this review is to discuss the majorfeatures of the GRN for hindbrain segmentation and its relationship to the broader functional role of the hindbrain in patterning head development.

Whole genome re-sequencing of crested traits and expression analysis of key candidate genes in duck

The crested duck was a duck breed which features a topknot of feathers on the back of their head. In order to explain the reason of crest, we anatomy the head of some crested ducks. The anatomical structures showed that there was a fat body in the head and a hole in the skull. To determine the reason for the formation of the crest, we used whole genome re-sequencing to detect SNPs and InDels in three crested duck and three normal crested duck (without crest). There were 785,202 unique SNPs and 105,596 unique InDels include in crested duck. There were 14,591 SNPs containing genes and 13,784 InDels continuing genes were mapped on BGI_duck_1.0 by BWA 0.7.16a software. We use KEGG and GO to classification the SNP and InDel containing genes function. The PPI network of SNP containing genes and InDels containing genes was constructed by STRING. The result of PPI and KEGG analysis shown that the formation of crest might include feather development, fatty acid deposition, and skull hypoplasia. To determine the regulated of SNP containing genes and InDels containing genes, which related the different trait, of miRNA we used mirmap to predicted target miRNA of those genes. The miRNA-genes network constructed by Cytoscape. In conclusion, the formation of the crest was a complex process. The fatty acid metabolism block, feather growth and skull hypoplasia might lead crest formation. The tissue expression of four candidate genes showed that they were closely related to the formation of the trait, and could be used as important candidate genes to further elaborate the molecular mechanism of their function.

Elucidating an Essential Role of Promoting Endothelial-to-Hematopoietic Transition By a Key EMT-Regulator ZEB2 Using a Human iPSC-Based Model

ZEB2 (Zinc finger E-box binding homeobox 2; also known as SMAD interacting protein-1 or SIP1) is a DNA-binding transcriptional regulator associated with epithelial-to-mesenchymal-transition (EMT). It has been reported that it is important in many other developmental processes, including mesoderm formation during gastrulation and neural crest formation. More recently, a study reported that inactivation of ZEB2 in mice results in differentiation defects in multiple hematopoietic cell lineages (1). In order to examine the roles of ZEB2 in human developmental process and hematopoiesis, we decided to apply human induced pluripotent stem cells (iPSCs) as a model with a pair of isogenic iPSCs with or without functional ZEB2 expression. We used a validated iPSC-based hematopoietic differentiation under a feeder- and xeno-free culture condition was used to study the role of ZEB2 in hematopoietic cell formation and to avoid other EMT-inducing factors in serum. We found that ZEB2 expression is abundant in either cord blood cells or human iPSCs-derived hematopoietic stem/progenitor cells (HSPCs), indicating that ZEB2 deficiency may hinder human hematopoietic differentiation. To knock out the ZEB2 gene and generate ZEB2 deficient human iPSCs, we used two different CRISPR guide RNAs as well as SpCas9 in a human iPSC line BC1. An engineered isogenic BC1 iPSC line that has both alleles 155-bp deletion in ZEB2 exon 1 (ZEB2 -/-) was successfully isolated and expanded, resulting in the frameshift and the consequent disappearance of ZEB2 protein expression. The complete ZEB2 knockout had little effects on human iPSCs expansion. However, we observed that the differentiation of ZEB-/- BC1 into CD34+CD45+ HSPCs was decreased. The number of ZEB-/- BC1-derived HSPCs was 5-fold lower than that from wide type BC1 control. Moreover, ZEB2-deleted HSPCs were defected in hematopoietic colony formation. To figure out at which hematopoietic differentiating stage the defects occurred, we applied inducible iPSC's endothelium-hematopoietic transformation (EHT) system to mimic hemogenic endothelial cells (ECs) giving rise to HSPCs. By using this established EHT system, ZEB2 deficient iPSCs were differentiated in order into CD34+CD31+CD144+ ECs, and then to HSPCs (2). We found that ZEB2 depletion did not adversely affect the formation of ECs from human iPSCs in this EHT experimental system but did impact on HSPCs generation from ECs. This study is unique in several ways to elucidate the roles of ZEB2 in human hematopoietic development. This prospective genetic model allowed us to pinpoint ZEB2 is critical at the stage of EHT during human hematopoietic cell formation. Our results indicate that contribution of ZEB2 deficiency in blood disorders might result from the inhibition of HSPC formation. The human iPSC-based hematopoietic differentiation system coupled with precisely edited isogenic iPSC lines also provide a more controlled genetic model for studying functions of others gene in their regulation of human hematopoiesis.

Network architecture and regulatory logic in neural crest development.

The neural crest is an ectodermal cell population that gives rise to over 30 cell types during vertebrate embryogenesis. These stem cells are formed at the border of the developing central nervous system and undergo extensive migration before differentiating into components of multiple tissues and organs. Neural crest formation and differentiation is a multistep process, as these cells transition through sequential regulatory states before adopting their adult phenotype. Such changes are governed by a complex gene regulatory network (GRN) that integrates environmental and cell-intrinsic inputs to regulate cell identity. Studies of neural crest cells in a variety of vertebrate models have elucidated the function and regulation of dozens of the molecular players that are part of this network. The neural crest GRN has served as a platform to explore the molecular control of multipotency, cell differentiation, and the evolution of vertebrates. In this review, we employ this genetic program as a stepping-stone to explore the architecture and the regulatory principles of developmental GRNs. We also discuss how modern genomic approaches can further expand our understanding of genetic networks in this system and others. This article is categorized under: Physiology > Mammalian Physiology in Health and Disease Biological Mechanisms > Cell Fates Developmental Biology > Lineages Models of Systems Properties and Processes > Cellular Models.

Sequence alteration in the enhancer contributes to the heterochronic Sox9 expression in marsupial cranial neural crest

Neonates of marsupial mammals are altricial at birth, because their gestation period is relatively short compared to placental mammals. Yet, as they need to travel to the teat from the birth canal, and suckle on the mother’s milk, forelimbs and jaws develop significantly early. Previous studies in opossum (Monodelphis domestica), an experimental marsupial model, have revealed that cranial neural crest cells are generated significantly early compared to those in placental mammals, such as mouse, leading to an early development of jaw primordia. We have previously found that Sox9, an important neural crest-specifier gene, is expressed in the future cranial neural crest of the opossum embryonic ectoderm significantly earlier than that in mouse or quail embryos. As Sox9 is essential for neural crest formation in various vertebrates, it seems likely that the heterochronic expression of Sox9 is critical for the early cranial neural crest formation in the marsupial embryos. In this study, we show a marsupial-specific sequence in the Sox9 neural crest enhancer E3. We also reveal that the mouse E3 enhancer is activated in the cranial neural crest cells of quail embryos, that the E3 enhancer with marsupial-specific sequence is activated earlier in the Pax7-expressing neural border prior to the onset of endogenous Sox9 expression, and that a misexpression of cMyb, which is also a transcriptional activator of Pax7, in the neural border can ectopically activate the “marsupialized” enhancer. Thus, we suggest that the modification of the E3 enhancer sequence in the marsupial ancestor would have promoted the early expression of Sox9 in the neural border, facilitating the early formation of the cranial neural crest cells and the subsequent heterochronic development of the jaw primordia.

Early expression of Tubulin Beta-III in avian cranial neural crest cells

Neural crest cells are a transient stem-like cell population that forms in the dorsal neural tube of vertebrate embryos and then migrates to various locations to differentiate into diverse derivatives such as craniofacial bone, cartilage, and the enteric and peripheral nervous systems. The current dogma of neural crest cell development suggests that there is a specific hierarchical gene regulatory network (GRN) that controls the induction, specification, and differentiation of these cells at specific developmental times. Our lab has identified that a marker of differentiated neurons, Tubulin Beta-III (TUBB3), is expressed in premigratory neural crest cells. TUBB3 has previously been identified as a major constituent of microtubules and is required for the proper guidance and maintenance of axons during development. Using the model organism, Gallus gallus, we have characterized the spatiotemporal localization of TUBB3 in early stages of development. Here we show TUBB3 is expressed in the developing neural plate, is upregulated in the pre-migratory cranial neural crest prior to cell delamination and migration, and it is maintained or upregulated in neurons in later developmental stages. We believe that TUBB3 likely has a role in early neural crest formation and migration separate from its role in neurogenesis.

The gene regulatory basis of genetic compensation during neural crest induction.

The neural crest (NC) is a vertebrate-specific cell type that contributes to a wide range of different tissues across all three germ layers. The gene regulatory network (GRN) responsible for the formation of neural crest is conserved across vertebrates. Central to the induction of the NC GRN are AP-2 and SoxE transcription factors. NC induction robustness is ensured through the ability of some of these transcription factors to compensate loss of function of gene family members. However the gene regulatory events underlying compensation are poorly understood. We have used gene knockout and RNA sequencing strategies to dissect NC induction and compensation in zebrafish. We genetically ablate the NC using double mutants of tfap2a;tfap2c or remove specific subsets of the NC with sox10 and mitfa knockouts and characterise genome-wide gene expression levels across multiple time points. We find that compensation through a single wild-type allele of tfap2c is capable of maintaining early NC induction and differentiation in the absence of tfap2a function, but many target genes have abnormal expression levels and therefore show sensitivity to the reduced tfap2 dosage. This separation of morphological and molecular phenotypes identifies a core set of genes required for early NC development. We also identify the 15 somites stage as the peak of the molecular phenotype which strongly diminishes at 24 hpf even as the morphological phenotype becomes more apparent. Using gene knockouts, we associate previously uncharacterised genes with pigment cell development and establish a role for maternal Hippo signalling in melanocyte differentiation. This work extends and refines the NC GRN while also uncovering the transcriptional basis of genetic compensation via paralogues.

SNAI1 recruits HDAC1 to suppress SNAI2 transcription during epithelial to mesenchymal transition

Aberrant activation of epithelial to mesenchymal transition (EMT) associated factors were highly correlated with increased mortality in cancer patients. SNAIL family of transcriptional repressors comprised of three members, each of which were essentially associated with gastrulation and neural crest formation. Among which, SNAI1 and SNAI2 were efficiently induced during EMT and their expressions were correlated with poor clinical outcome in patients with breast, colon and ovarian carcinoma. In an ovarian cancer cell lines panel, we identified that SNAI1 and SNAI2 expressions were mutually exclusive, where SNAI1 predominantly represses SNAI2 expression. Detailed analysis of SNAI2 promoter region revealed that SNAI1 binds to two E-box sequences that mediated transcriptional repression. Through epigenetic inhibitor treatments, we identified that inhibition of histone deacetylase (HDAC) activity in SNAI1 overexpressing cells partially rescued SNAI2 expression. Importantly, we demonstrated a significant deacetylation of histone H3 and significant enrichments of HDAC1 and HDAC2 corepressors in both E-box regions of SNAI2 promoter. Our results suggested that SNAI1 repression on SNAI2 expression was predominantly mediated through the recruitment of the histone deacetylation machinery. Utilization of HDAC inhibitors would require additional profiling of SNAI1 activity and combined targeting of SNAI1 and HDACs might render efficient cancer treatment.

FGF Modulates the Axial Identity of Trunk hPSC-Derived Neural Crest but Not the Cranial-Trunk Decision.

SummaryThe neural crest is a transient embryonic tissue that gives rise to a multitude of derivatives in an axially restricted manner. An in vitro counterpart to neural crest can be derived from human pluripotent stem cells (hPSCs) and can be used to study neural crest ontogeny and neurocristopathies, and to generate cells for therapeutic purposes. In order to successfully do this, it is critical to define the specific conditions required to generate neural crest of different axial identities, as regional restriction in differentiation potential is partly cell intrinsic. WNT and FGF signaling have been implicated as inducers of posterior fate, but the exact role that these signals play in trunk neural crest formation remains unclear. Here, we present a fully defined, xeno-free system for generating trunk neural crest from hPSCs and show that FGF signaling directs cells toward different axial identities within the trunk compartment while WNT signaling is the primary determinant of trunk versus cranial identity.

Modes of Berm and Beachface Recovery Following Storm Reset: Observations Using a Continuously Scanning Lidar

AbstractFollowing the rapid and destructive impacts of storm erosion, beach recovery is a key natural process of restoration, returning eroded sediment to the subaerial beach and rebuilding coastal morphology. While the effects of storm erosion have commonly been investigated, detailed studies into poststorm recovery are currently lacking. This study investigates wave‐driven recovery processes of the berm and beachface on a microtidal, swash‐aligned sandy beach. Following complete removal of the berm by a significant storm event, the entire 76‐day rebuilding of a swash berm is analyzed at the timescale of every semidiurnal tidal cycle, utilizing high‐resolution (5 Hz) swash and subaerial beach profile measurements from a continuously scanning fixed lidar. Tide‐by‐tide rates of subaerial volume change during berm recovery were most frequently observed between 1 and 2 m3/m/day, including losses and gains an order of magnitude larger than the more gradual rate of net gain (0.7 m3/m/day) observed for the entire recovery period. Patterns of berm crest formation and vertical growth were found to be primarily governed by the neap‐spring tide variations in total water levels. Tide‐by‐tide beachface and berm volume changes were used to classify four principal behavioral modes of subaerial profile variability during recovery. Using decision tree classification, modes were differentiated according to nearshore dimensionless fall velocity, swash exceedance of the berm crest, and ocean water levels. The findings provide novel behavioral and parametric insight into the tide‐by‐tide rebuilding of the beachface and berm by swash throughout a complete poststorm recovery period.