Neural tube defects （NTDs） are severe congenital malformation diseases, which occur in 1 out of 1000 births in human. In Xenopus, several tissue movements are involved in the neural tube closure process. Immediately...Neural tube defects （NTDs） are severe congenital malformation diseases, which occur in 1 out of 1000 births in human. In Xenopus, several tissue movements are involved in the neural tube closure process. Immediately after the neural tube fusion, the neural crest cells get monopolar protrusion toward dorsal midline and migrate to form the roof of the neural tube. At the same time, radial intercalation takes place from the ventral neural tube and forces it to be single-layered. Here, we physically block the neural tube closure to test the cell movements and the following patterning in Xenopus laevis explants. The results show that the single-layered neural tube fails to form and the neural crest cells remain at the lateral regions in the explants with NTDs. However, the patterning of the neural tube is not affected as indicated by the normal expression of the preneural genes. These results indicate a requirement of the neural tube fusion for the radial intercalation and the dorsal midline directed neural crest migration, but not for the dorsal-ventral patterning of the neural tube.展开更多
Cell migration is a finely tuned biological process that often involves epithelial-mesenchymal transition(EMT).EMT is typically characterized by the upregulation of mesenchymal markers such as Snail1.This process has ...Cell migration is a finely tuned biological process that often involves epithelial-mesenchymal transition(EMT).EMT is typically characterized by the upregulation of mesenchymal markers such as Snail1.This process has been shown to be of critical importance to normal developmental processes,including neural crest migration and invasion.Interestingly,similar mechanisms are utilized in disease processes,such as tumor metastasis and migration.Notably,EMT and EMT-like processes confer tumor cells with the ability to migrate,invade,and adopt stem cell-like properties that largely account for immunosuppression and tumor recurrence.Therefore,identifying sensitive EMT markers may contribute to cancer prognosis and diagnosis in many facets.Previously,we showed that Elp3 plays an essential role during neural crest migration by stabilizing Snail1.In the current study,we further elucidate the molecular mechanism underlying colorectal cancer migration.We found that mElp3 exerted an identical function to xElp3 in modulating neural crest migration,and both HAT and SAM domains are imperative during this migratory process.Interestingly,overexpression of mElp3 in SW480 cells promoted cell migration and invasion,and we further showed that Elp3 stabilized Snail1 requiring integrity of both SAM and HAT domains.Our findings warrant further exploration of the specific target of Elp3 in cancer cells.展开更多
The peripheral nerve injuries,representing some of the most common types of traumatic lesions affecting the nervous system,are highly invalidating for the patients besides being a huge social burden.Although periphera...The peripheral nerve injuries,representing some of the most common types of traumatic lesions affecting the nervous system,are highly invalidating for the patients besides being a huge social burden.Although peripheral nervous system owns a higher regenerative capacity than does central nervous system,mostly depending on Schwann cells intervention in injury repair,several factors determine the extent of functional outcome after healing.Based on the injury type,different therapeutic approaches have been investigated so far.Nerve grafting and Schwann cell transplantation have represented the gold standard treatment for peripheral nerve injuries,however these approaches own limitations,such as scarce donor nerve availability and donor site morbidity.Cell based therapies might provide a suitable tool for peripheral nerve regeneration,in fact,the ability of different stem cell types to differentiate towards Schwann cells in combination with the use of different scaffolds have been widely investigated in animal models of peripheral nerve injuries in the last decade.Dental pulp is a promising cell source for regenerative medicine,because of the ease of isolation procedures,stem cell proliferation and multipotency abilities,which are due to the embryological origin from neural crest.In this article we review the literature concerning the application of tooth derived stem cell populations combined with different conduits to peripheral nerve injuries animal models,highlighting their regenerative contribution exerted through either glial differentiation and neuroprotective/neurotrophic effects on the host tissue.展开更多
Background Folic acid is very important for embryonic development and dihydrofolate reductase is one of the key enzymes in the process of fotic acid performing its biological function. Therefore, the dysfunction of di...Background Folic acid is very important for embryonic development and dihydrofolate reductase is one of the key enzymes in the process of fotic acid performing its biological function. Therefore, the dysfunction of dihydrofolate reductase can inhibit the function of folic acid and finally cause the developmental malformations. In this study, we observed the abnormal cardiac phenotypes in dihydrofolate reductase （DHFR） gene knock-down zebrafish embryos, investigated the effect of DHFR on the expression of heart and neural crest derivatives expressed transcript 2 （HAND2） and explored the possible mechanism of DHFR knock-down inducing zebrafish cardiac malformations. Methods Morpholino oligonucleotides were microinjected into fertilized eggs to knock down the functions of DHFR or HAND2. Full length of HAND2 mRNA which was transcribed in vitro was microinjected into fertilized eggs to overexpress HAND2. The cardiac morphologies, the heart rates and the ventricular shortening fraction were observed and recorded under the microscope at 48 hours post fertilization. Whole-mount in situ hybridization and real-time PCR were performed to detect HAND2 expression. Results DHFR or HAND2 knock-down caused the cardiac malformation in zebrafish. The expression of HAND2 was obviously reduced in DHFR knock-down embryos （P〈0.05）. Microinjecting HAND2 mRNA into fertilized eggs can induce HAND2 overexpression. HAND2 overexpression rescued the cardiac malformation phenotypes of DHFR knock-down embryos. Conclusions DHFR plays a crucial role in cardiac development. The down-regulation of HAND2 caused by DHFR knock-down is the possible mechanism of DHFR knock-down inducing the cardiac malformation.展开更多
Microtubules play important roles in mitotic spindle assembly and chromosome segregation to maintain normal cell cycle progression.A number of microtubule-associated proteins have been identified in epithelial and neu...Microtubules play important roles in mitotic spindle assembly and chromosome segregation to maintain normal cell cycle progression.A number of microtubule-associated proteins have been identified in epithelial and neural cell cultures;however,their physiological significance is not well characterized due to the lack of appropriate in vivo animal models.Nucleolar spindleassociated protein(NuSAP)is a microtubule-binding protein and is reported to be involved in mitosis by cell culture studies.In this report,we identified the zebrafish homologue of human NuSAP and investigated its expression profile and functions.Using in situ hybridization,we demonstrated that transcripts of zebrafish nusap1 are specifically expressed in the retina,forebrain,hindbrain and neural crest.When the in vivo expression of nusap1 was knocked down through antisense oligonucleotide morpholino technology,the morphants of nusap1 showed impaired morphogenesis in the trunk and yolk extension,implying the involvement of Nusap1 in cell migration.Mechanistic studies revealed that nusap1 morphants have an altered expression pattern of neural crest markers crestin and sox9b,but normal expression of blood vessel and notochord markers gata1 and shh.In addition,nusap1 mRNA injection caused serious apoptosis in retina and hindbrain tissue,and these phenotypes can be rescued by co-injection of morpholino against nusap1.These observations not only suggest a role for Nusap1 in connecting apoptosis with cell migration,but also provide strong evidences that Nusap1 is potentially involved in morphogenesis in vertebrates.展开更多
The dental pulp has irreplaceable roles in maintaining healthy teeth and its regeneration is a primary aim of regenerative endodontics.This study aimed to replicate the characteristics of dental pulp tissue by using c...The dental pulp has irreplaceable roles in maintaining healthy teeth and its regeneration is a primary aim of regenerative endodontics.This study aimed to replicate the characteristics of dental pulp tissue by using cranial neural crest(CNC)-like cells(CNCLCs);these cells were generated by modifying several steps of a previously established method for deriving NC-like cells from induced pluripotent stem cells(iPSCs).CNC is the anterior region of the neural crest in vertebrate embryos,which contains the primordium of dental pulp cells or odontoblasts.The produced CNCLCs showed approximately 2.5-12,000-fold upregulations of major CNC marker genes.Furthermore,the CNCLCs exhibited remarkable odontoblastic differentiation ability,especially when treated with a combination of the fibroblast growth factors(FGFs)FGF4 and FGF9.The FGFs induced odontoblast marker genes by 1.7-5.0-fold,as compared to bone morphogenetic protein 4(BMP4)treatment.In a mouse subcutaneous implant model,the CNCLCs briefly fated with FGF4+FGF9 replicated dental pulp tissue characteristics,such as harboring odontoblast-like cells,a dentin-like layer,and vast neovascularization,induced by the angiogenic self-assembling peptide hydrogel(SAPH),SLan.SLan acts as a versatile biocompatible scaffold in the canal space.This study demonstrated a successful collaboration between regenerative medicine and SAPH technology.展开更多
Neogenin is a transmembrane receptor critical for multiple cellular processes,including neurogenesis,astrogliogenesis,endochondral bone formation,and iron homeostasis.Here we present evidence that loss of neogenin con...Neogenin is a transmembrane receptor critical for multiple cellular processes,including neurogenesis,astrogliogenesis,endochondral bone formation,and iron homeostasis.Here we present evidence that loss of neogenin contributes to pathogenesis of persistent hyperplastic primary vitreous(PHPV)formation,a genetic disorder accounting for^5% of blindness in the USA.Selective loss of neogenin in neural crest cells(as observed in Wntl-Cre;Neofff mice),but not neural stem cells(as observed in GFAP-Cre and Nestin-Cre;Neo^f/f mice),resulted in a dysregulation of neural crest cell migration or delamination,exhibiting features of PHPV-like pathology(e.g.elevated retrolental mass),unclosed retinal fissure,and microphthalmia.These results demonstrate an unrecognized function of neogenin in preventing PHPV pathogenesis,implicating neogenin regulation of neural crest cell delamination/migration and retinal fissure formation as potential underlying mechanisms of PHPV.展开更多
The TBX1 gene is considered to be the most important gene in the aetiology of DiGeorge syndrome （DGS）.DGS is a human disorder characterised by a number of phenotypic features involving abnormal development of pharyn...The TBX1 gene is considered to be the most important gene in the aetiology of DiGeorge syndrome （DGS）.DGS is a human disorder characterised by a number of phenotypic features involving abnormal development of pharyngeal arches, facial dysmorphogenesis and cardiac outflow tract anomalies. Retinoic acid （RA） deficiency also produces DGS-like phenotypes. The affectd tissues in DGS are derivatives of neural crest cells （NCCs）, which originate from the border between the neural plate and non-neural ectoderm, migrate to specific destinations in the body, and generate a variety of derivatives. In our study, we have explored the hypothesis that tbxl affects NCC development in zebrafish by regulating RA signaling.展开更多
The cranial neural crest(CNC)cells play a vital role in craniofacial development and regeneration.They are multi-potent progenitors,being able to differentiate into various types of tissues.Both pre-migratory and post...The cranial neural crest(CNC)cells play a vital role in craniofacial development and regeneration.They are multi-potent progenitors,being able to differentiate into various types of tissues.Both pre-migratory and post-migratory CNC cells are plastic,taking on diverse fates by responding to different inductive signals.However,what sustains the multipotency ofCNCcells andderivatives remains largely unknown.In this study,we present evidence that FGF8 signaling is able to sustain progenitor status and multipotency of CNC-derived mesenchymal cells both in vivo and in vitro.We show that augmented FGF8 signaling in pre-migratory CNC cells prevents cell differentiation and organogenesis in the craniofacial region by maintaining their progenitor status.CNC-derived mesenchymal cells with Fgf8 overexpression or control cells in the presence of exogenous FGF8 exhibit prolonged survival,proliferation,and multi-potent differentiation capability in cell cultures.Remarkably,exogenous FGF8 also sustains the capability of CNC-derived mesenchymal cells to participate in organogenesis such as odontogenesis.Furthermore,FGF8-mediated signaling strongly promotes adipogenesis but inhibits osteogenesis of CNC-derived mesenchymal cells in vitro.Our results reveal a specific role for FGF8 in the maintenance of progenitor status and in fate determination of CNC cells,implicating a potential application in expansion and fate manipulation of CNC-derived cells in stem cell-based craniofacial regeneration.展开更多
The member of Rho family of small GTPases Cdc42 plays important and conserved roles in cell polarity and motility. The Cdc42ep family proteins have been identified to bind to Cdc42, yet how they interact with Cdc42 to...The member of Rho family of small GTPases Cdc42 plays important and conserved roles in cell polarity and motility. The Cdc42ep family proteins have been identified to bind to Cdc42, yet how they interact with Cdc42 to regulate cell migration remains to be elucidated. In this study, we focus on Cdc42epl, which is expressed predominantly in the highly migratory neural crest ceils in frog embryos. Through morpholino-mediated knockdown, we show that Cdc42epl is required for the migration of cranial neural crest cells. Loss of Cdc42epl leads to rounder cell shapes and the formation of membrane blebs, consistent with the observed disruption in actin organization and focal adhesion alignment. As a result, Cdc42ep1 is critical for neural crest cells to apply traction forces at the correct place to migrate efficiently. We further show that Cdc42ep1 is localized to two areas in neural crest celts： in membrane protrusions together with Cdc42 and in perinuciear patches where Cdc42 is absent. Cdc42 directly interacts with Cdc42epl （through the CRIB domain） and changes in Cdc42 level shift the distribution of Cdc42epl between these two subcellular locations, controlling the formation of membrane protrusions and directionality of migration as a consequence. These results suggest that Cdc42ep1 elaborates Cdc42 activity in neural crest cells to promote their efficient migration.展开更多
Retinoic acid (RA) plays an important role in development of vertebrate embryos. We demonstrate impacts of exogenous RA on the formation of neural crest cells in zebrafish using specific neural crest markers sox9b and...Retinoic acid (RA) plays an important role in development of vertebrate embryos. We demonstrate impacts of exogenous RA on the formation of neural crest cells in zebrafish using specific neural crest markers sox9b and crestin. Treatment with all-trans RA at 10-7 mmol/L at 50% epiboly induces sox9b expression in the forebrain and crestin expression in the forebrain and midbrain, resulting in significant increase of pigment cells in the head derived from the cranial neural crest. In addition, RA treatment induces expression of sox9b and crestin in the caudal marginal cells of the neuroectoderm during early segmentation. Earlier commitment of these cells to the neural crest fate in the posterior margins leads to abnormal development of the posterior body, probably by preventing mingling of ventral derived and dorsal-derived cells during the formation of the tailbud.展开更多
This paper develops a nonlinear mathematical model to simulate the dynamic motion behavior of the barge equipped with the portable outboard Dynamic Positioning （DP） system in short-crested waves. The self-tuning Pro...This paper develops a nonlinear mathematical model to simulate the dynamic motion behavior of the barge equipped with the portable outboard Dynamic Positioning （DP） system in short-crested waves. The self-tuning Proportional- Derivative （PD） controller based on the neural network algorithm is applied to control the thrusters for optimal adjustment of the barge position in waves. In addition to the wave, the current, the wind and the nonlinear drift force are also considered in the calculations. The time domain simulations for the six-degree-of-freedom motions of the barge with the DP system are solved by the 4th order Runge-Kutta method which can compromise the efficiency and the accuracy of the simulations. The technique of the portable alternative DP system developed here can serve as a practical tool to assist those ships without being equipped with the DP facility while the dynamic positioning missions are needed.展开更多
基金supported by grants from the National Natural Science Foundation of China (30425011 30530380)the Innovation Project of the Chinese Academy of Sciences (KSCX2-YW-R-090)~~
文摘Neural tube defects （NTDs） are severe congenital malformation diseases, which occur in 1 out of 1000 births in human. In Xenopus, several tissue movements are involved in the neural tube closure process. Immediately after the neural tube fusion, the neural crest cells get monopolar protrusion toward dorsal midline and migrate to form the roof of the neural tube. At the same time, radial intercalation takes place from the ventral neural tube and forces it to be single-layered. Here, we physically block the neural tube closure to test the cell movements and the following patterning in Xenopus laevis explants. The results show that the single-layered neural tube fails to form and the neural crest cells remain at the lateral regions in the explants with NTDs. However, the patterning of the neural tube is not affected as indicated by the normal expression of the preneural genes. These results indicate a requirement of the neural tube fusion for the radial intercalation and the dorsal midline directed neural crest migration, but not for the dorsal-ventral patterning of the neural tube.
基金supported by the National Natural Science Foundation of China(Grant Nos.81760503 and 81760660)the Applied Basic Research Key Project of Yunnan(Grant Nos.2018FE001(-318)and 2018FE001(-123))the Yunnan Health Science and Technology Plan Projects(Grant No.2016NS207).
文摘Cell migration is a finely tuned biological process that often involves epithelial-mesenchymal transition(EMT).EMT is typically characterized by the upregulation of mesenchymal markers such as Snail1.This process has been shown to be of critical importance to normal developmental processes,including neural crest migration and invasion.Interestingly,similar mechanisms are utilized in disease processes,such as tumor metastasis and migration.Notably,EMT and EMT-like processes confer tumor cells with the ability to migrate,invade,and adopt stem cell-like properties that largely account for immunosuppression and tumor recurrence.Therefore,identifying sensitive EMT markers may contribute to cancer prognosis and diagnosis in many facets.Previously,we showed that Elp3 plays an essential role during neural crest migration by stabilizing Snail1.In the current study,we further elucidate the molecular mechanism underlying colorectal cancer migration.We found that mElp3 exerted an identical function to xElp3 in modulating neural crest migration,and both HAT and SAM domains are imperative during this migratory process.Interestingly,overexpression of mElp3 in SW480 cells promoted cell migration and invasion,and we further showed that Elp3 stabilized Snail1 requiring integrity of both SAM and HAT domains.Our findings warrant further exploration of the specific target of Elp3 in cancer cells.
文摘The peripheral nerve injuries,representing some of the most common types of traumatic lesions affecting the nervous system,are highly invalidating for the patients besides being a huge social burden.Although peripheral nervous system owns a higher regenerative capacity than does central nervous system,mostly depending on Schwann cells intervention in injury repair,several factors determine the extent of functional outcome after healing.Based on the injury type,different therapeutic approaches have been investigated so far.Nerve grafting and Schwann cell transplantation have represented the gold standard treatment for peripheral nerve injuries,however these approaches own limitations,such as scarce donor nerve availability and donor site morbidity.Cell based therapies might provide a suitable tool for peripheral nerve regeneration,in fact,the ability of different stem cell types to differentiate towards Schwann cells in combination with the use of different scaffolds have been widely investigated in animal models of peripheral nerve injuries in the last decade.Dental pulp is a promising cell source for regenerative medicine,because of the ease of isolation procedures,stem cell proliferation and multipotency abilities,which are due to the embryological origin from neural crest.In this article we review the literature concerning the application of tooth derived stem cell populations combined with different conduits to peripheral nerve injuries animal models,highlighting their regenerative contribution exerted through either glial differentiation and neuroprotective/neurotrophic effects on the host tissue.
文摘Background Folic acid is very important for embryonic development and dihydrofolate reductase is one of the key enzymes in the process of fotic acid performing its biological function. Therefore, the dysfunction of dihydrofolate reductase can inhibit the function of folic acid and finally cause the developmental malformations. In this study, we observed the abnormal cardiac phenotypes in dihydrofolate reductase （DHFR） gene knock-down zebrafish embryos, investigated the effect of DHFR on the expression of heart and neural crest derivatives expressed transcript 2 （HAND2） and explored the possible mechanism of DHFR knock-down inducing zebrafish cardiac malformations. Methods Morpholino oligonucleotides were microinjected into fertilized eggs to knock down the functions of DHFR or HAND2. Full length of HAND2 mRNA which was transcribed in vitro was microinjected into fertilized eggs to overexpress HAND2. The cardiac morphologies, the heart rates and the ventricular shortening fraction were observed and recorded under the microscope at 48 hours post fertilization. Whole-mount in situ hybridization and real-time PCR were performed to detect HAND2 expression. Results DHFR or HAND2 knock-down caused the cardiac malformation in zebrafish. The expression of HAND2 was obviously reduced in DHFR knock-down embryos （P〈0.05）. Microinjecting HAND2 mRNA into fertilized eggs can induce HAND2 overexpression. HAND2 overexpression rescued the cardiac malformation phenotypes of DHFR knock-down embryos. Conclusions DHFR plays a crucial role in cardiac development. The down-regulation of HAND2 caused by DHFR knock-down is the possible mechanism of DHFR knock-down inducing the cardiac malformation.
基金grant from National Nature Science Foundation of China(Grant No.30900748)Natural Science Foundation in Fujian province(Grant No.2009J01194)H.H.and Chinese National Basic Research Programs(Grant No.2006CB910802)to H.F.
文摘Microtubules play important roles in mitotic spindle assembly and chromosome segregation to maintain normal cell cycle progression.A number of microtubule-associated proteins have been identified in epithelial and neural cell cultures;however,their physiological significance is not well characterized due to the lack of appropriate in vivo animal models.Nucleolar spindleassociated protein(NuSAP)is a microtubule-binding protein and is reported to be involved in mitosis by cell culture studies.In this report,we identified the zebrafish homologue of human NuSAP and investigated its expression profile and functions.Using in situ hybridization,we demonstrated that transcripts of zebrafish nusap1 are specifically expressed in the retina,forebrain,hindbrain and neural crest.When the in vivo expression of nusap1 was knocked down through antisense oligonucleotide morpholino technology,the morphants of nusap1 showed impaired morphogenesis in the trunk and yolk extension,implying the involvement of Nusap1 in cell migration.Mechanistic studies revealed that nusap1 morphants have an altered expression pattern of neural crest markers crestin and sox9b,but normal expression of blood vessel and notochord markers gata1 and shh.In addition,nusap1 mRNA injection caused serious apoptosis in retina and hindbrain tissue,and these phenotypes can be rescued by co-injection of morpholino against nusap1.These observations not only suggest a role for Nusap1 in connecting apoptosis with cell migration,but also provide strong evidences that Nusap1 is potentially involved in morphogenesis in vertebrates.
基金supported by NIH grants,R01DE025885(E.S),R15EY029504(VAK)National Science Foundation NSF IIP 1903617(VAK).
文摘The dental pulp has irreplaceable roles in maintaining healthy teeth and its regeneration is a primary aim of regenerative endodontics.This study aimed to replicate the characteristics of dental pulp tissue by using cranial neural crest(CNC)-like cells(CNCLCs);these cells were generated by modifying several steps of a previously established method for deriving NC-like cells from induced pluripotent stem cells(iPSCs).CNC is the anterior region of the neural crest in vertebrate embryos,which contains the primordium of dental pulp cells or odontoblasts.The produced CNCLCs showed approximately 2.5-12,000-fold upregulations of major CNC marker genes.Furthermore,the CNCLCs exhibited remarkable odontoblastic differentiation ability,especially when treated with a combination of the fibroblast growth factors(FGFs)FGF4 and FGF9.The FGFs induced odontoblast marker genes by 1.7-5.0-fold,as compared to bone morphogenetic protein 4(BMP4)treatment.In a mouse subcutaneous implant model,the CNCLCs briefly fated with FGF4+FGF9 replicated dental pulp tissue characteristics,such as harboring odontoblast-like cells,a dentin-like layer,and vast neovascularization,induced by the angiogenic self-assembling peptide hydrogel(SAPH),SLan.SLan acts as a versatile biocompatible scaffold in the canal space.This study demonstrated a successful collaboration between regenerative medicine and SAPH technology.
文摘Neogenin is a transmembrane receptor critical for multiple cellular processes,including neurogenesis,astrogliogenesis,endochondral bone formation,and iron homeostasis.Here we present evidence that loss of neogenin contributes to pathogenesis of persistent hyperplastic primary vitreous(PHPV)formation,a genetic disorder accounting for^5% of blindness in the USA.Selective loss of neogenin in neural crest cells(as observed in Wntl-Cre;Neofff mice),but not neural stem cells(as observed in GFAP-Cre and Nestin-Cre;Neo^f/f mice),resulted in a dysregulation of neural crest cell migration or delamination,exhibiting features of PHPV-like pathology(e.g.elevated retrolental mass),unclosed retinal fissure,and microphthalmia.These results demonstrate an unrecognized function of neogenin in preventing PHPV pathogenesis,implicating neogenin regulation of neural crest cell delamination/migration and retinal fissure formation as potential underlying mechanisms of PHPV.
基金This work was supported by the grants from the National Natural Science Foundation of China （No. 30772352 and No. 30972959）.
文摘The TBX1 gene is considered to be the most important gene in the aetiology of DiGeorge syndrome （DGS）.DGS is a human disorder characterised by a number of phenotypic features involving abnormal development of pharyngeal arches, facial dysmorphogenesis and cardiac outflow tract anomalies. Retinoic acid （RA） deficiency also produces DGS-like phenotypes. The affectd tissues in DGS are derivatives of neural crest cells （NCCs）, which originate from the border between the neural plate and non-neural ectoderm, migrate to specific destinations in the body, and generate a variety of derivatives. In our study, we have explored the hypothesis that tbxl affects NCC development in zebrafish by regulating RA signaling.
基金This work was supported by the National Institutes of Health(R01DE24152 and R01DE14044 to Y.C.)the National Basic Research Program of China(2010CB944800)to W.T.the National Natural Science Foundation of China(81371134)to T.H.
文摘The cranial neural crest(CNC)cells play a vital role in craniofacial development and regeneration.They are multi-potent progenitors,being able to differentiate into various types of tissues.Both pre-migratory and post-migratory CNC cells are plastic,taking on diverse fates by responding to different inductive signals.However,what sustains the multipotency ofCNCcells andderivatives remains largely unknown.In this study,we present evidence that FGF8 signaling is able to sustain progenitor status and multipotency of CNC-derived mesenchymal cells both in vivo and in vitro.We show that augmented FGF8 signaling in pre-migratory CNC cells prevents cell differentiation and organogenesis in the craniofacial region by maintaining their progenitor status.CNC-derived mesenchymal cells with Fgf8 overexpression or control cells in the presence of exogenous FGF8 exhibit prolonged survival,proliferation,and multi-potent differentiation capability in cell cultures.Remarkably,exogenous FGF8 also sustains the capability of CNC-derived mesenchymal cells to participate in organogenesis such as odontogenesis.Furthermore,FGF8-mediated signaling strongly promotes adipogenesis but inhibits osteogenesis of CNC-derived mesenchymal cells in vitro.Our results reveal a specific role for FGF8 in the maintenance of progenitor status and in fate determination of CNC cells,implicating a potential application in expansion and fate manipulation of CNC-derived cells in stem cell-based craniofacial regeneration.
基金This work is supported by the National Institutes of Health （ROODE022796 to S.N.） and National Science Foundation （DMR- 0955811 to J.E.C. and PHY-0848797 to J.E.C. and D.T.K.）.
文摘The member of Rho family of small GTPases Cdc42 plays important and conserved roles in cell polarity and motility. The Cdc42ep family proteins have been identified to bind to Cdc42, yet how they interact with Cdc42 to regulate cell migration remains to be elucidated. In this study, we focus on Cdc42epl, which is expressed predominantly in the highly migratory neural crest ceils in frog embryos. Through morpholino-mediated knockdown, we show that Cdc42epl is required for the migration of cranial neural crest cells. Loss of Cdc42epl leads to rounder cell shapes and the formation of membrane blebs, consistent with the observed disruption in actin organization and focal adhesion alignment. As a result, Cdc42ep1 is critical for neural crest cells to apply traction forces at the correct place to migrate efficiently. We further show that Cdc42ep1 is localized to two areas in neural crest celts： in membrane protrusions together with Cdc42 and in perinuciear patches where Cdc42 is absent. Cdc42 directly interacts with Cdc42epl （through the CRIB domain） and changes in Cdc42 level shift the distribution of Cdc42epl between these two subcellular locations, controlling the formation of membrane protrusions and directionality of migration as a consequence. These results suggest that Cdc42ep1 elaborates Cdc42 activity in neural crest cells to promote their efficient migration.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 30025020 and 39970360)TRAPOYT of the MOE.
文摘Retinoic acid (RA) plays an important role in development of vertebrate embryos. We demonstrate impacts of exogenous RA on the formation of neural crest cells in zebrafish using specific neural crest markers sox9b and crestin. Treatment with all-trans RA at 10-7 mmol/L at 50% epiboly induces sox9b expression in the forebrain and crestin expression in the forebrain and midbrain, resulting in significant increase of pigment cells in the head derived from the cranial neural crest. In addition, RA treatment induces expression of sox9b and crestin in the caudal marginal cells of the neuroectoderm during early segmentation. Earlier commitment of these cells to the neural crest fate in the posterior margins leads to abnormal development of the posterior body, probably by preventing mingling of ventral derived and dorsal-derived cells during the formation of the tailbud.
基金financially supported by the Science Council Taiwan (Grant No. NSC-96-2221-E006-329-MY3)partly supported by the Research Center of Ocean Environment and Technology NCKU
文摘This paper develops a nonlinear mathematical model to simulate the dynamic motion behavior of the barge equipped with the portable outboard Dynamic Positioning （DP） system in short-crested waves. The self-tuning Proportional- Derivative （PD） controller based on the neural network algorithm is applied to control the thrusters for optimal adjustment of the barge position in waves. In addition to the wave, the current, the wind and the nonlinear drift force are also considered in the calculations. The time domain simulations for the six-degree-of-freedom motions of the barge with the DP system are solved by the 4th order Runge-Kutta method which can compromise the efficiency and the accuracy of the simulations. The technique of the portable alternative DP system developed here can serve as a practical tool to assist those ships without being equipped with the DP facility while the dynamic positioning missions are needed.
