Pharyngeal arch deficiencies affect taste bud development in the circumvallate papilla with aberrant glossopharyngeal nerve formation

BACKGROUND

The pharyngeal arches (PAs) generate cranial organs including the tongue. The taste placodes, formed in particular locations on the embryonic tongue surface, differentiate into taste buds harbored in distinct gustatory papillae. The developing tongue also has a complex supply of cranial nerves through each PA. However, the relationship between the PAs and taste bud development is not fully understood.

RESULTS

Ripply3 homozygous mutant mice, which have impaired third/fourth PAs, display a hypoplastic circumvallate papilla and lack taste buds, although the taste placode is normally formed. Formation of the glossopharyngeal ganglia is defective and innervation toward the posterior tongue is completely missing in Ripply3 mutant embryos at E12.5. Moreover, the distribution of neuroblasts derived from the epibranchial placode is severely, but not completely, atenuated, and the neural crest cells are diminished in the third PA region of Ripply3 mutant embryos at E9.5-E10.5. In Tbx1 homozygous mutant embryos, which exhibit another type of deficiency in PA development, the hypoplastic circumvallate papilla is observed along with abnormal formation of the glossopharyngeal ganglia and severely impaired innervation.

CONCLUSIONS

PA deficiencies affect multiple aspects of taste bud development, including formation of the cranial ganglia and innervation to the posterior tongue.

Notch signaling regulates venous arterialization during zebrafish fin regeneration

To protect against blood pressure, a mature artery is supported by mural cells which include vascular smooth muscle cells and pericytes. To regenerate a functional vascular system, arteries should be properly reconstructed with mural cells although the mechanisms underlying artery reconstruction remain unclear. In this study, we examined the process of artery reconstruction during regeneration of the zebrafish caudal fin as a model to study arterial formation in an adult setting. During fin regeneration, the arteries and veins form a net-like vasculature called the vascular plexus, and this plexus undergoes remodeling to form a new artery and two flanking veins. We found that the new vascular plexus originates mainly from venous cells in the stump but very rarely from the arterial cells. Interestingly, these vein-derived cells contributed to the reconstructed arteries. This arterialization was dependent on Notch signaling, and further analysis showed that Notch signaling was required for the initiation of arterial gene expression. In contrast, venous remodeling did not require Notch signaling. These results provide new insights toward understanding mechanisms of vascular regeneration and illustrate the utility of the adult zebrafish fin to study this process.

Tbx protein level critical for clock-mediated somite positioning is regulated through interaction between Tbx and Ripply

Somitogenesis in vertebrates is a complex and dynamic process involving many sequences of events generated from the segmentation clock. Previous studies with mouse embryos revealed that the presumptive somite boundary is periodically created at the anterior border of the expression domain of Tbx6 protein. Ripply1 and Ripply2 are required for the determination of the Tbx6 protein border, but the mechanism by which this Tbx6 domain is regulated remains unclear. Furthermore, since zebrafish and frog Ripplys are known to be able to suppress Tbx6 function at the transcription level, it is also unclear whether Ripply-mediated mechanism of Tbx6 regulation is conserved among different species. Here, we tested the generality of Tbx6 protein-mediated process in somite segmentation by using zebrafish and further examined the mechanism of regulation of Tbx6 protein. By utilizing an antibody against zebrafish Tbx6/Fss, previously referred to as Tbx24, we found that the anterior border of Tbx6 domain coincided with the presumptive intersomitic boundary even in the zebrafish and it shifted dynamically during 1 cycle of segmentation. Consistent with the findings in mice, the tbx6 mRNA domain was located far anterior to its protein domain, indicating the possibility of posttranscriptional regulation. When both ripply1/2 were knockdown, the Tbx6 domain was anteriorly expanded. We further directly demonstrated that Ripply could reduce the expression level of Tbx6 protein depending on physical interaction between Ripply and Tbx6. Moreover, the onset of ripply1 and ripply2 expression occurred after reduction of FGF signaling at the anterior PSM, but this expression initiated much earlier on treatment with SU5402, a chemical inhibitor of FGF signaling. These results strongly suggest that Ripply is a direct regulator of the Tbx6 protein level for the establishment of intersomitic boundaries and mediates a reduction in FGF signaling for the positioning of the presumptive intersomitic boundary in the PSM.

Transmission phase in the Kondo regime revealed in a two-path interferometer

We report on the direct observation of the transmission phase shift through a Kondo correlated quantum dot by employing a new type of two-path interferometer. We observed a clear π/2-phase shift, which persists up to the Kondo temperature TK. Above this temperature, the phase shifts by more than π/2 at each Coulomb peak, approaching the behavior observed for the standard Coulomb blockade regime. These observations are in remarkable agreement with two-level numerical renormalization group calculations. The unique combination of experimental and theoretical results presented here fully elucidates the phase evolution in the Kondo regime.

Insm1 promotes endocrine cell differentiation by modulating the expression of a network of genes that includes Neurog3 and Ripply3

Insulinoma associated 1 (Insm1) plays an important role in regulating the development of cells in the central and peripheral nervous systems, olfactory epithelium and endocrine pancreas. To better define the role of Insm1 in pancreatic endocrine cell development we generated mice with an Insm1^GFPCre reporter allele and used them to study Insm1-expressing and null populations. Endocrine progenitor cells lacking Insm1 were less differentiated and exhibited broad defects in hormone production, cell proliferation and cell migration. Embryos lacking Insm1 contained greater amounts of a non-coding Neurog3 mRNA splice variant and had fewer Neurog3/Insm1 co-expressing progenitor cells, suggesting that Insm1 positively regulates Neurog3. Moreover, endocrine progenitor cells that express either high or low levels of Pdx1, and thus may be biased towards the formation of specific cell lineages, exhibited cell type-specific differences in the genes regulated by Insm1. Analysis of the function of Ripply3, an Insm1-regulated gene enriched in the Pdx1-high cell population, revealed that it negatively regulates the proliferation of early endocrine cells. Taken together, these findings indicate that in developing pancreatic endocrine cells Insm1 promotes the transition from a ductal progenitor to a committed endocrine cell by repressing a progenitor cell program and activating genes essential for RNA splicing, cell migration, controlled cellular proliferation, vasculogenesis, extracellular matrix and hormone secretion.

Leucophores are similar to xanthophores in their specification and differentiation processes in medaka

Animal body color is generated primarily by neural crest-derived pigment cells in the skin. Mammals and birds have only melanocytes on the surface of their bodies; however, fish have a variety of pigment cell types or chromatophores, including melanophores, xanthophores, and iridophores. The medaka has a unique chromatophore type called the leucophore. The genetic basis of chromatophore diversity remains poorly understood. Here, we report that three loci in medaka, namely, leucophore free (lf), lf-2, and white leucophore (wl), which affect leucophore and xanthophore differentiation, encode solute carrier family 2, member 15b (slc2a15b), paired box gene 7a (pax7a), and solute carrier family 2 facilitated glucose transporter, member 11b (slc2a11b), respectively. Because lf-2, a loss-of-function mutant for pax7a, causes defects in the formation of xanthophore and leucophore precursor cells, pax7a is critical for the development of the chromatophores. This genetic evidence implies that leucophores are similar to xanthophores, although it was previously thought that leucophores were related to iridophores, as these chromatophores have purine-dependent light reflection. Our identification of slc2a15b and slc2a11b as genes critical for the differentiation of leucophores and xanthophores in medaka led to a further finding that the existence of these two genes in the genome coincides with the presence of xanthophores in nonmammalian vertebrates: birds have yellow-pigmented irises with xanthophore-like intracellular organelles. Our findings provide clues for revealing diverse evolutionary mechanisms of pigment cell formation in animals.

Metameric pattern of intervertebral disc/vertebral body is generated independently of Mesp2/Ripply-mediated rostro-caudal patterning of somites in the mouse embryo

The vertebrae are derived from the sclerotome of somites. Formation of the vertebral body involves a process called resegmentation, by which the caudal half of a sclerotome is combined with the rostral half of the next sclerotome. To elucidate the relationship between resegmentation and rostro-caudal patterning of somite, we used the Uncx4.1-LacZ transgene to characterize the resegmentation process. Our observations suggested that in the thoracic and lumbar vertebrae, the Uncx4.1-expressing caudal sclerotome gave rise to the intervertebral disc (IVD) and rostral portion of the vertebral body (VB). In the cervical vertebrae, the Uncx4.1-expressing caudal sclerotome appeared to contribute to the IVD and both caudal and rostral ends of the VB. This finding suggests that the rostro-caudal gene expression boundary does not necessarily coincide with the resegmentation boundary. This conclusion was supported by analyses of Mesp2 KO and Ripply1/2 double KO embryos lacking rostral and caudal properties, respectively. Resegmentation was not observed in Mesp2 KO embryos, but both the IVD and whole VB were formed from the caudalized sclerotome. Expression analysis of IVD marker genes including Pax1 in the wild-type, Mesp2 KO, and Ripply1/2 DKO embryos also supported the idea that a metameric pattern of IVD/VB is generated independently of Mesp2/Ripply-mediated rostro-caudal patterning of somite. However, in the lumbar region, IVD differentiation appeared to be stimulated by the caudal property and suppressed by the rostral property. Therefore, we propose that rostro-caudal patterning of somites is not a prerequisite for metameric patterning of the IVD and VB, but instead required to stimulate IVD differentiation in the caudal half of the sclerotome.

Functional cooperation of spns2 and fibronectin in cardiac and lower jaw development

The lipid mediator sphingosine-1-phosphate (S1P) is a regulator of cardiac development in zebrafish, as disruption of its receptor s1pr2 or transporter spns2 causes migration defects in cardiac progenitors. To examine the genetic interaction of S1P signaling and the cell adhesion molecule fibronectin, we have established a fn;spns2 double mutant. Cardiac migration defects in fn;spns2 mutants were more severe than those in fn or spns2 mutants. We further found that the lower jaw morphology was disorganized in the fn;spns2 mutant, while it had a slightly shortened anterior–posterior distance in the ventral pharyngeal arch in fn and spns2 mutants relative to wild type. Knockdown of fn in the s1pr2 mutant, but not in the s1pr1 mutant, resulted in severe defects in cardiac migration and ventral pharyngeal arch arrangement. Further, in the background of the fn mutant, knockdown of endothelin receptor A (ednra), which was downregulated in the spns2 mutant, caused pharyngeal defects resembling those in the fn;spns2 mutant. These results strongly suggest that Spns2-S1PR2 signaling and fibronectin cooperatively regulate both cardiac and lower jaw development in zebrafish.

Quantification of changes in metamorphopsia and retinal contraction in eyes with spontaneous separation of idiopathic epiretinal membrane

BACKGROUND

To quantify changes in metamorphopsia and retinal contraction in eyes with idiopathic epiretinal membrane (ERM) before and after a spontaneous separation of ERM.

METHODS

Among 92 eyes of 92 patients with idiopathic ERM who were followed up at our hospital, 5 eyes of 5 patients had experienced a spontaneous separation of ERM during the follow-up period. Patient's metamorphopsia was assessed horizontally and vertically by a metamorphopsia chart developed by our group, M-CHARTS, to obtain the horizontal (MH) and vertical (MV) metamorphopsia scores. Difference in the scores before and after the membrane separation represents change in patient's metamorphopsia. Changes in retinal contraction were also evaluated horizontally and vertically with our original software for fundus image analysis. The difference between M-CHARTS scores and distances of retinal vessel movements with before and after membrane separation were measured.

RESULTS

All five subjects showed a decrease in the retinal contraction. Improved visual acuity was observed in three subjects, and no change was seen in the other two. Four subjects obtained better metamorphopsia scores after the membrane separation, while the other one was not detected with metamorphopsia by M-CHARTS either before or after the separation. In subjects with an improved MV, horizontal retinal movement was seen larger than the vertical movement. Similarly, the subjects with an improved MH indicated a larger vertical retinal movement than the horizontal movement.

CONCLUSIONS

The direction of patient's metamorphopsia closely associated with the direction of retinal contraction before and after a spontaneous separation of ERM.

High-Strength PET Fibers Produced by Conjugated Melt Spinning and Laser Drawing

The mechanical properties of conjugated-spun and laser drawn poly(ethylene terephthalate) (PET) fibers were investigated. The as-spun fibers used for the laser drawing were made by conjugated melt spinning with the copolymer of p-hydroxybenzoicacid and 2-hydroxy-6-naphthoicacid or polystyrene. The PET fibers prepared by conjugated spinning could be laser drawn to higher draw ratios under lower drawing stresses. The drawn fiber could be re-drawn up to a higher total draw ratio. Thus, a PET fiber having a tensile strength of 1.14 N/tex could be produced.

Hepatitis B virus DNA integration frequently observed in the hepatocellular carcinoma DNA of hepatitis C virus-infected patients

Human hepatitis B virus (HBV) and hepatitis C virus (HCV) are two major etiologic agents of chronic hepatitis, which is closely related to the development of hepatocellular carcinoma (HCC). We investigated the role of HBV coinfection in ongoing HCV-related liver diseases in HCV-infected patients. We found a high prevalence of anti-HBc in anti-HCV-positive/HBsAg-negative HCC patients and also found a close correlation between anti-HBc positivity and integration of HBV DNA into HCC DNA of anti-HCV-positive/HBsAg-negative patients. The present data suggest that integrated HBV DNA may play an important role in the development of HCC in the anti-HCV-positive/HBsAg-negative patients carrying the anti-HBc antibody.

Mesogenin causes embryonic mesoderm progenitors to differentiate during development of zebrafish tail somites

The molecular mechanism underlying somite development differs along the embryonic antero-posterior axis. In zebrafish, cell lineage tracing and genetic analysis have revealed a difference in somite development between the trunk and tail. For instance, spadetail/tbx16 (spt) mutant embryos lack trunk somites but not tail ones. Trunk and tail somites are developed from mesodermal progenitor cells (MPCs) located in the tailbud. While the undifferentiated state of MPCs is maintained by mutual activation between Wnt and Brachyury/Ntl, the mechanism by which the MPCs differentiate into presomitic mesoderm (PSM) cells remains largely unclear. Especially, the molecules that promote PSM differentiation during tail development should be clarified. Here, we show that zebrafish embryos defective in mesogenin1 (msgn1) and spt failed to differentiate into PSM cells in tail development and show increased expression of wnt8 and ntl. Msgn1 acted in a cell-autonomous manner and as a transcriptional activator in PSM differentiation. The expression of msgn1 initially overlapped with that of ntl in the ventral tailbud, as previously reported; and its mis-expression caused ectopic expression of tbx24, a PSM marker gene, only in the tailbud and posterior notochord, both of which expressed ntl in zebrafish embryos. Furthermore, the PSM-inducing activity of misexpressed msgn1 was enhanced by co-expression with ntl. Thus, Msgn1 exercised its PSM-inducing activity in cells expressing ntl. Based on these results, we speculate that msgn1 expression in association with that of ntl may allow the differentiation of progenitor cells to proceed during development of somites in the tail.

Immunohistochemical investigation of lymphatic vessel formation control in mouse tooth development: lymphatic vessel-forming factors and receptors in tooth development in mice

The presence of lymphatic vessels in dental pulp has recently been controversial, and no conclusion has been reached. In this study, we investigated the control of lymphangiogenesis with dental pulp development in the mouse mandibular molar using VEGF-C, VEGF-D, and VEGFR-3 as indices of lymphatic vessel-controlling factors. In addition, to distinguish blood and lymphatic vascular epithelial cells, we performed immunohistochemical analysis using von Willebrand factor (vWF) and statistical analysis. In dental papilla in the bell-stage non-calcified period, mesenchymal cells positive for VEGF-C, VEGF-D, and VEGFR-3 increased and lumen-forming endothelial cells were noted, but vWF was negative, suggesting that these were actively forming lymphatic vessels. Positive undifferentiated mesenchymal cells, an increase in endothelial cells in dental pulp, and lumen expansion were noted early after birth. Positivity was also detected in the odontoblast layer and sheath of Hertwig after birth, suggesting that these factors also play important roles in odontoblast differentiation and maturation and periodontal ligament and tooth root formation. We embryologically clarified lymphatic vessel formation in dental pulp and a process of lymphatic vessel formation from blood vessels, suggesting involvement of the surrounding tissue, odontoblasts, and sheath of Hertwig in vessel formation.

Loss of Porcupine impairs convergent extension during gastrulation in zebrafish

Porcupine (Porcn), an O-acyltransferase located in the endoplasmic reticulum (ER), is required for lipidation of Wnt proteins to enable their trafficking from the ER in mammalian cell culture. However, it is unclear whether Porcn is required for trafficking of all members of the Wnt family. In this study, we investigated the function of Porcn in zebrafish embryos. We identified two zebrafish homologs of porcupine, porcn and porcupine-like (porcn-l). Zebrafish porcn, but not porcn-l, restores secretion of Wnt proteins in porcn-deficient mouse L cells. Morpholino-mediated knockdown of porcn in zebrafish embryos impairs convergence and extension (CE) during gastrulation without changing embryonic patterning. Moreover, porcn interacts genetically with wnt5b and wnt11 in regulating CE. By contrast, porcn-deficient embryos do not exhibit phenotypes caused by failure in canonical Wnt signaling, which is activated by several Wnt ligands, including Wnt3a. Furthermore, expression of genes regulated by the canonical Wnt signaling pathway is not perturbed in knockdown embryos relative to that in controls. Although the trafficking and lipidation of ectopically expressed zebrafish Wnt5b and mouse Wnt5a are impaired in porcn-deficient embryos, those of ectopically expressed Wnt3a are less or not affected. In addition, the secretion of Wnt5a is inhibited by less Porcn inhibitor than that of Wnt3a in HEK293T cells. Thus, a decrease of Porcn activity does not equivalently affect trafficking and lipidation of different Wnt proteins in zebrafish embryos and in cultured mammalian cells.

Ripply3, a Tbx1 repressor, is required for development of the pharyngeal apparatus and its derivatives in mice

The pharyngeal apparatus is a transient structure that gives rise to the thymus and the parathyroid glands and also contributes to the development of arteries and the cardiac outflow tract. A typical developmental disorder of the pharyngeal apparatus is the 22q11 deletion syndrome (22q11DS), for which Tbx1 is responsible. Here, we show that Ripply3 can modulate Tbx1 activity and plays a role in the development of the pharyngeal apparatus. Ripply3 expression is observed in the pharyngeal ectoderm and endoderm and overlaps with strong expression of Tbx1 in the caudal pharyngeal endoderm. Ripply3 suppresses transcriptional activation by Tbx1 in luciferase assays in vitro. Ripply3-deficient mice exhibit abnormal development of pharyngeal derivatives, including ectopic formation of the thymus and the parathyroid gland, as well as cardiovascular malformation. Corresponding with these defects, Ripply3-deficient embryos show hypotrophy of the caudal pharyngeal apparatus. Ripply3 represses Tbx1-induced expression of Pax9 in luciferase assays in vitro, and Ripply3-deficient embryos exhibit upregulated Pax9 expression. Together, our results show that Ripply3 plays a role in pharyngeal development, probably by regulating Tbx1 activity.

Wnt3a promotes hippocampal neurogenesis by shortening cell cycle duration of neural progenitor cells

The effects of Wnt signaling on neural progenitor cells have been controversial. Activation of the canonical Wnt signaling pathway either promotes neural progenitor cell proliferation or accelerates their differentiation into postmitotic neurons. This study demonstrates that activation of the Wnt signaling pathway by itself induces neural progenitor cell proliferation but does not directly affect neuronal differentiation processes. To investigate whether Wnt signaling promotes expansion and/or differentiation of neural progenitor cells in the developing hippocampus, we prepared primary mouse hippocampal progenitors and treated them with Wnt3a in a chemically defined culture medium. Wnt3a increased the total number of cells, including the numbers of Ki67(+) proliferating cells and Tuj1(+) differentiated neurons. This result verified that Wnt3a promoted neural progenitor cell proliferation. Meanwhile, Wnt3a did not appear to actively enhance the neuronal differentiation process itself, because (1) the ratio of Tuj1(+) cells to the total cells, and (2) the ratio of BrdU(+) Tuj1(+) cells to the total BrdU(+) cells, were both comparable between cultures with or without Wnt3a. Indeed, Wnt3a caused no significant change in either cell survival or the proportion of symmetric and asymmetric cell divisions that directly affected neuron production. We finally demonstrated that the Wnt3a treatment simply shortened cell cycle duration of neural progenitor cells by 2.9 h. The accelerated cell cycle progression without affecting the ratio of symmetric/asymmetric cell divisions explains how Wnt signaling per se leads to the expansion of both proliferative cell population and differentiated neuronal cell population.