Automated FRET quantification shows distinct subcellular ERK activation kinetics in response to graded EGFR signaling in Drosophila.

Threshold responses to an activity gradient allow a single signaling pathway to yield multiple outcomes. Extracellular signal-regulated kinase (ERK) is one such signal, which couples receptor tyrosine kinase signaling with multiple cellular responses in various developmental processes. Recent advances in the development of fluorescent biosensors for live imaging have enabled the signaling activities accompanying embryonic development to be monitored in real time. Here, we used an automated computational program to quantify the signals of a fluorescence resonance energy transfer (FRET) reporter for activated ERK, and we used this system to monitor the spatio-temporal dynamics of ERK during neuroectoderm patterning in Drosophila embryos. We found that the cytoplasmic and nuclear ERK activity gradients show distinct kinetics in response to epidermal growth factor receptor activation. The ERK activation patterns implied that the cytoplasmic ERK activity is modulated into a threshold response in the nucleus.

IKKε inhibits PKC to promote Fascin-dependent actin bundling.

Signaling molecules have pleiotropic functions and are activated by various extracellular stimuli. Protein kinase C (PKC) is activated by diverse receptors, and its dysregulation is associated with diseases including cancer. However, how the undesired activation of PKC is prevented during development remains poorly understood. We have previously shown that a protein kinase, IKKε, is active at the growing bristle tip and regulates actin bundle organization during Drosophila bristle morphogenesis. Here, we demonstrate that IKKε regulates the actin bundle localization of a dynamic actin cross-linker, Fascin. IKKε inhibits PKC, thereby protecting Fascin from inhibitory phosphorylation. Excess PKC activation is responsible for the actin bundle defects in IKKε-deficient bristles, whereas PKC is dispensable for bristle morphogenesis in wild-type bristles, indicating that PKC is repressed by IKKε in wild-type bristle cells. These results suggest that IKKε prevents excess activation of PKC during bristle morphogenesis.

Emerging mechanisms regulating mitotic synchrony during animal embryogenesis.

The basic mechanisms controlling mitosis are highly conserved in animals regardless of cell types and developmental stages. However, an exceptional aspect of mitosis is seen during early animal embryogenesis in which a large fertilized egg is quickly divided into smaller blastomeres according to the reproducible spatiotemporal pattern that does not rely on the cell-cycle arrest or growth. This mitosis, referred to as cleavage, overlaps in the timeframe with the specification of cell fate. The precise spatiotemporal regulation of cleavages is therefore essential to the creation of the appropriate cell number and to the morphology of an embryo. To achieve the reproducibility of cleavage during embryogenesis, the relative timing of mitosis between cells, which we refer to as synchrony, must be properly regulated. Studies in model organisms have begun to reveal how the synchrony of mitosis is regulated by the developmental modulation of cell-cycle machineries. In this review, we focus on three such mechanisms: biochemical switches that achieve the synchrony of mitosis, the nucleo-cytoplasmic ratio that provokes the asynchrony of mitosis, and the transcriptional mechanisms coupled with cell fate control that reestablish the synchrony of mitosis in each fate-restricted compartment. Our review is an attempt to understand the temporal patterns of cleavages in animal embryos created by the combinations of these three mechanisms.

Ependymal cells of chordate larvae are stem-like cells that form the adult nervous system.

In ascidian tunicates, the metamorphic transition from larva to adult is accompanied by dynamic changes in the body plan. For instance, the central nervous system (CNS) is subjected to extensive rearrangement because its regulating larval organs are lost and new adult organs are created. To understand how the adult CNS is reconstructed, we traced the fate of larval CNS cells during ascidian metamorphosis by using transgenic animals and imaging technologies with photoconvertible fluorescent proteins. Here we show that most parts of the ascidian larval CNS, except for the tail nerve cord, are maintained during metamorphosis and recruited to form the adult CNS. We also show that most of the larval neurons disappear and only a subset of cholinergic motor neurons and glutamatergic neurons are retained. Finally, we demonstrate that ependymal cells of the larval CNS contribute to the construction of the adult CNS and that some differentiate into neurons in the adult CNS. An unexpected role of ependymal cells highlighted by this study is that they serve as neural stem-like cells to reconstruct the adult nervous network during chordate metamorphosis. Consequently, the plasticity of non-neuronal ependymal cells and neuronal cells in chordates should be re-examined by future studies.

Hox10-regulated endodermal cell migration is essential for development of the ascidian intestine.

Hox cluster genes play crucial roles in development of the metazoan antero-posterior axis. Functions of Hox genes in patterning the central nervous system and limb buds are well known. They are also expressed in chordate endodermal tissues, where their roles in endodermal development are still poorly understood. In the invertebrate chordate, Ciona intestinalis, endodermal tissues are in a premature state during the larval stage, and they differentiate into the digestive tract during metamorphosis. In this study, we showed that disruption of a Hox gene, Ci-Hox10, prevented intestinal formation. Ci-Hox10-knock-down larvae displayed defective migration of endodermal strand cells. Formation of a protrusion, which is important for cell migration, was disrupted in these cells. The collagen type IX gene is a downstream target of Ci-Hox10, and is negatively regulated by Ci-Hox10 and a matrix metalloproteinase ortholog, prior to endodermal cell migration. Inhibition of this regulation prevented cellular migration. These results suggest that Ci-Hox10 regulates endodermal strand cell migration by forming a protrusion and by reconstructing the extracellular matrix.

Transcriptional regulation of a horizontally transferred gene from bacterium to chordate.

The horizontal transfer of genes between distantly related organisms is undoubtedly a major factor in the evolution of novel traits. Because genes are functionless without expression, horizontally transferred genes must acquire appropriate transcriptional regulations in their recipient organisms, although the evolutionary mechanism is not known well. The defining characteristic of tunicates is the presence of a cellulose containing tunic covering the adult and larval body surface. Cellulose synthase was acquired by horizontal gene transfer from Actinobacteria. We found that acquisition of the binding site of AP-2 transcription factor was essential for tunicate cellulose synthase to gain epidermal-specific expression. Actinobacteria have very GC-rich genomes, regions of which are capable of inducing specific expression in the tunicate epidermis as the AP-2 binds to a GC-rich region. Therefore, the actinobacterial cellulose synthase could have been potentiated to evolve its new function in the ancestor of tunicates with a higher probability than the evolution depending solely on a spontaneous event.

Retinoic acid-driven Hox1 is required in the epidermis for forming the otic/atrial placodes during ascidian metamorphosis.

Retinoic acid (RA)-mediated expression of the homeobox gene Hox1 is a hallmark of the chordate central nervous system (CNS). It has been suggested that the RA-Hox1 network also functions in the epidermal ectoderm of chordates. Here, we show that in the urochordate ascidian Ciona intestinalis, RA-Hox1 in the epidermal ectoderm is necessary for formation of the atrial siphon placode (ASP), a structure homologous to the vertebrate otic placode. Loss of Hox1 function resulted in loss of the ASP, which could be rescued by expressing Hox1 in the epidermis. As previous studies showed that RA directly upregulates Hox1 in the epidermis of Ciona larvae, we also examined the role of RA in ASP formation. We showed that abolishment of RA resulted in loss of the ASP, which could be rescued by forced expression of Hox1 in the epidermis. Our results suggest that RA-Hox1 in the epidermal ectoderm played a key role in the acquisition of the otic placode during chordate evolution.

Immediate therapeutic efficacy of low-density lipoprotein apheresis for drug-resistant nephrotic syndrome: evidence from the short-term results from the POLARIS Study.

BACKGROUND: Hyperlipidemia is not merely a complication but a major exacerbating factor in longstanding nephrotic syndrome (NS). Low-density lipoprotein apheresis (LDL-A) has been reported to ameliorate dyslipidemia and induce rapid remission of NS. Several clinical studies have suggested the therapeutic efficacy of LDL-A, but the level of clinical evidence is insufficient. Therefore, a multicenter prospective study, POLARIS (Prospective Observational Survey on the Long-Term Effects of LDL Apheresis on Drug-Resistant Nephrotic Syndrome), was initiated in Japan. METHOD: Patients with drug-resistant NS were prospectively recruited into the study and treated with LDL-A in facilities that were registered in advance. In the POLARIS study design, the clinical data are to be followed up for 2 years. In the current study, we aimed at evaluating the short-term efficacy based on the treatment outcome of LDL-A immediately after completion of treatment. RESULTS: Along with rapid improvement of hyperlipidemia, LDL-A significantly improved proteinuria and hypoproteinemia after treatment. More than half of the patients showed remission of NS based on the urinary protein level at the completion of LDL-A. The duration of NS before the start of treatment was significantly shorter in patients who responded to LDL-A. CONCLUSIONS: An analysis of patients registered in the POLARIS study indicated that LDL-A has short-term efficacy for drug-resistant NS. Rapid relief of dyslipidemia by LDL-A may provide early remission in about half of the NS patients who are resistant to conventional medication. Completion of the POLARIS study may reveal additional long-term effects of LDL-A in these patients.

Nonreproductive role of gonadotropin-releasing hormone in the control of ascidian metamorphosis.

BACKGROUND: Gonadotropin-releasing hormones (GnRHs) are neuropeptides that play central roles in the reproduction of vertebrates. In the ascidian Ciona intestinalis, GnRHs and their receptors are expressed in the nervous systems at the larval stage, when animals are not yet capable of reproduction, suggesting that the hormones have non-reproductive roles. RESULTS: We showed that GnRHs in Ciona are involved in the animal's metamorphosis by regulating tail absorption and adult organ growth. Absorption of the larval tail and growth of the adult organs are two major events in the metamorphosis of ascidians. When larvae were treated with GnRHs, they completed tail absorption more frequently than control larvae. cAMP was suggested to be a second messenger for the induction of tail absorption by GnRHs. tGnRH-3 and tGnRH-5 (the "t" indicates "tunicate") inhibited the growth of adult organs by arresting cell cycle progression in parallel with the promotion of tail absorption. CONCLUSIONS: This study provides new insights into the molecular mechanisms of ascidian metamorphosis conducted by non-reproductive GnRHs.

Coordination of mitosis and morphogenesis: role of a prolonged G2 phase during chordate neurulation.

Chordates undergo a characteristic morphogenetic process during neurulation to form a dorsal hollow neural tube. Neurulation begins with the formation of the neural plate and ends when the left epidermis and right epidermis overlying the neural tube fuse to close the neural fold. During these processes, mitosis and the various morphogenetic movements need to be coordinated. In this study, we investigated the epidermal cell cycle in Ciona intestinalis embryos in vivo using a fluorescent ubiquitination-based cell cycle indicator (Fucci). Epidermal cells of Ciona undergo 11 divisions as the embryos progress from fertilization to the tadpole larval stage. We detected a long G2 phase between the tenth and eleventh cell divisions, during which fusion of the left and right epidermis occurred. Characteristic cell shape change and actin filament regulation were observed during the G2 phase. CDC25 is probably a key regulator of the cell cycle progression of epidermal cells. Artificially shortening this G2 phase by overexpressing CDC25 caused precocious cell division before or during neural tube closure, thereby disrupting the characteristic morphogenetic movement. Delaying the precocious cell division by prolonging the S phase with aphidicolin ameliorated the effects of CDC25. These results suggest that the long interphase during the eleventh epidermal cell cycle is required for neurulation.

Formation of the digestive tract in Ciona intestinalis includes two distinct morphogenic processes between its anterior and posterior parts.

BACKGROUND: In the ascidian Ciona intestinalis, the digestive tract, an essential system for animals, develops during metamorphosis from the two primordial tissues, the endoderm and endodermal strand, located in the larval trunk and tail, respectively. However, it has been largely unknown how the digestive tract develops from these primordial tissues. We examined the metamorphosing larvae for the tubular formation of the digestive tract, focusing on the epithelial organization of the endoderm, by combined confocal microscopy and computational rendering. RESULTS: The tubular structure of the esophagus to the stomach was formed through the folding and closure of the endodermal epithelia in the central-to-right posterior trunk. By contrast, the intestine was formed in the left posterior trunk through the accumulation and rearrangement of the cells originated from the endodermal strand. This was confirmed by the cell-tracing experiment using Kaede expression construct driven in the endodermal strand. Thus, the tubular formation of the digestive tract in C. intestinalis includes distinct morphogenetic processes and cell lineages between its anterior and posterior parts. CONCLUSION: This study provides the first detailed description of the digestive tract morphogenesis in C. intestinalis and serves as an important basis toward thorough understanding of its digestive tract development.

Ascidians as excellent chordate models for studying the development of the nervous system during embryogenesis and metamorphosis.

The swimming larvae of the chordate ascidians possess a dorsal hollowed central nervous system (CNS), which is homologous to that of vertebrates. Despite the homology, the ascidian CNS consists of a countable number of cells. The simple nervous system of ascidians provides an excellent experimental system to study the developmental mechanisms of the chordate nervous system. The neural fate of the cells consisting of the ascidian CNS is determined in both autonomous and non-autonomous fashion during the cleavage stage. The ascidian neural plate performs the morphogenetic movement of neural tube closure that resembles that in vertebrate neural tube formation. Following neurulation, the CNS is separated into five distinct regions, whose homology with the regions of vertebrate CNS has been discussed. Following their larval stage, ascidians undergo a metamorphosis and become sessile adults. The metamorphosis is completed quickly, and therefore the metamorphosis of ascidians is a good experimental system to observe the reorganization of the CNS during metamorphosis. A recent study has shown that the major parts of the larval CNS remain after the metamorphosis to form the adult CNS. In contrast to such a conserved manner of CNS reorganization, most larval neurons disappear during metamorphosis. The larval glial cells in the CNS are the major source for the formation of the adult CNS, and some of the glial cells produce adult neurons.

Superazaporphyrins: meso-pentaazapentaphyrins and one of their low-symmetry derivatives.

Supersized: Three pentaazapentaphyrin derivatives, that is, the superazaporphyrins (SAzPs), as well as a superphthalocyanine (SPc) and a mixed low-symmetry derivative have been prepared and characterized. Decaaryl SAzPs have a distorted (4n+2) π structure and show the Q bands at about λ=840-880 nm. These compounds are relatively air stable.

Mid1 is associated with androgen-dependent axonal vulnerability of motor neurons in spinal and bulbar muscular atrophy.

Spinal and bulbar muscular atrophy (SBMA) is an adult-onset hereditary neurodegenerative disease caused by the expansions of CAG repeats in the androgen receptor (AR) gene. Androgen-dependent nuclear accumulation of pathogenic AR protein causes degeneration of lower motor neurons, leading to progressive muscle weakness and atrophy. While the successful induction of SBMA-like pathology has been achieved in mouse models, mechanisms underlying motor neuron vulnerability remain unclear. In the present study, we performed a transcriptome-based screening for genes expressed exclusively in motor neurons and dysregulated in the spinal cord of SBMA mice. We found upregulation of Mid1 encoding a microtubule-associated RNA binding protein which facilitates the translation of CAG-expanded mRNAs. Based on the finding that lower motor neurons begin expressing Mid1 during embryonic stages, we developed an organotypic slice culture system of the spinal cord obtained from SBMA mouse fetuses to study the pathogenic role of Mid1 in SBMA motor neurons. Impairment of axonal regeneration arose in the spinal cord culture in SBMA mice in an androgen-dependent manner, but not in mice with non-CAG-expanded AR, and was either exacerbated or ameliorated by Mid1 overexpression or knockdown, respectively. Hence, an early Mid1 expression confers vulnerability to motor neurons, at least by inducing axonogenesis defects, in SBMA.

Efficient transposition of a single Minos transposon copy in the genome of the ascidian Ciona intestinalis with a transgenic line expressing transposase in eggs.

Transgenesis with transposons is an important technique for studying genetic functions. In the ascidian Ciona intestinalis, methods for germline transformation with the Tc1/mariner transposon Minos have been established. A system to remobilize a single Minos copy in the genome is needed to refine this transgenic technique. In this study, such an experimental system was established with a transgenic line expressing Minos transposase in eggs. In the eggs of a double transgenic animal from a cross between the egg transposase line and a transgenic line having a single Minos insertion, the transposon was transposed into new positions of the Ciona genome, thus creating new insertions. Some of the new insertions caused enhancer detection. The majority of the new insertion sites were mapped on different chromosomes from that of the transposon donor. This characteristic of Minos is in contrast to that of the Sleeping Beauty transposon, which causes frequent intrachromosomal transposition.

ERK signaling dynamics in the morphogenesis and homeostasis of Drosophila.

Receptor tyrosine kinases (RTK) are transmembrane kinases that receive signals for intercellular communication to help organize body plan and sustain tissue homeostasis. These signals converge into the major signaling module of ERK, which transduces signals to the cytoplasm and nucleus. How this module responds to multiple RTK signals, and specifies unique outcomes in each cell, is still poorly understood. Recent technological advances in the quantitative imaging of ERK activity and its manipulation have yielded significant information on the cellular logic behind ERK activation and its readout in the context of Drosophila development. While in the pregastrulation stage, ERK plays a decisive on/off switch; its role changes to modulatory functions of morphogenesis and tissue quality control in the late embryonic stages.

A Switch-like Activation Relay of EGFR-ERK Signaling Regulates a Wave of Cellular Contractility for Epithelial Invagination.

The dynamics of extracellular signal-regulated kinase (ERK) signaling underlies its versatile functions in cell differentiation, cell proliferation, and cell motility. Classical studies in Drosophila established that a gradient of epidermal growth factor receptor (EGFR)-ERK signaling is essential for these cellular responses. However, we challenge this view by the real-time monitoring of ERK activation; we show that a switch-like ERK activation is essential for the invagination movement of the Drosophila tracheal placode. This switch-like ERK activation stems from the positive feedback regulation of the EGFR-ERK signaling and a resultant relay of EGFR-ERK signaling among tracheal cells. A key transcription factor Trachealess (Trh) permissively regulates the iteration of the relay, and the ERK activation becomes graded in trh mutant. A mathematical model based on these observations and a molecular link between ERK activation dynamics and myosin shows that the relay mechanism efficiently promotes epithelial invagination while the gradient mechanism does not.

Developmental Control of Cell-Cycle Compensation Provides a Switch for Patterned Mitosis at the Onset of Chordate Neurulation.

During neurulation of chordate ascidians, the 11th mitotic division within the epidermal layer shows a posterior-to-anterior wave that is precisely coordinated with the unidirectional progression of the morphogenetic movement. Here we show that the first sign of this patterned mitosis is an asynchronous anterior-to-posterior S-phase length and that mitotic synchrony is reestablished by a compensatory asynchronous G2-phase length. Live imaging combined with genetic experiments demonstrated that compensatory G2-phase regulation requires transcriptional activation of the G2/M regulator cdc25 by the patterning genes GATA and AP-2. The downregulation of GATA and AP-2 at the onset of neurulation leads to loss of compensatory G2-phase regulation and promotes the transition to patterned mitosis. We propose that such developmentally regulated cell-cycle compensation provides an abrupt switch to spatially patterned mitosis in order to achieve the coordination between mitotic timing and morphogenesis.

Switching the rate and pattern of cell division for neural tube closure.

The morphogenetic movement associated with neural tube closure (NTC) requires both positive and negative regulations of cell proliferation. The dual requirement of cell division control during NTC underscores the importance of the developmental control of cell division. In the chordate ascidian, midline fusions of the neural ectoderm and surface ectoderm (SE) proceed in the posterior-to-anterior direction, followed by a single wave of asynchronous and patterned cell division in SE. Before NTC, SE exhibits synchronous mitoses; disruption of the synchrony causes a failure of NTC. Therefore, NTC is the crucial turning point at which SE switches from synchronous to patterned mitosis. Our recent work discovered that the first sign of patterned cell division in SE appears was an asynchronous S-phase length along the anterior-posterior axis before NTC: the asynchrony of S-phase is offset by the compensatory G2-phase length, thus maintaining the apparent synchrony of cell division. By the loss of compensatory G2 phase, the synchronized cell division harmoniously switches to a patterned cell division at the onset of NTC. Here we review the developmental regulation of rate and pattern of cell division during NTC with emphasis on the switching mechanism identified in our study.

Effect of orally administered shao-yao-gan-cao-tang (Shakuyaku-kanzo-to) on muscle cramps in maintenance hemodialysis patients: a preliminary study.

Muscle cramps are one of the most common complications of hemodialysis (HD), and often are a source of great pain in spite of various clinical measures. The traditional herbal medicine, shao-yao-gan-cao-tang (Japanese name: Shakuyaku-kanzo-to), consists of equal amounts of paeony and licorice roots, and has been used in Japan and China for muscle pain or skeletal muscle tremors. To determine whether this medicine is able to prevent frequent and unendurable muscle cramps in patients undergoing HD, Shakuyaku-kanzo-to at 6 g per day was prospectively administered for 4 weeks to five patients on HD who were suffering from frequent muscle cramps. The frequency and severity of cramping before and after the treatment treatment were carefully observed and compared. Skeletal muscle cramps completely disappeared in two of the treated patients after the start of oral administration of Shakuyaku-kanzo-to. Moreover, the frequency of cramping was significantly decreased in two of the remaining three patients after persistent administration. The severity of muscle cramps was also decreased by this treatment in the responsive patients. No serious side effects were detected during the treatment period. The inhibitory effect of Shakuyaku-kanzo-to on muscle contraction was also experimentally examined by using phrenic nerve-diaphragm preparations from male Wistar rats. Differences between the twitch responses were determined when the diaphragms and the nerves were stimulated in the presence and absence of the extract of Shakuyaku-kanzo-to. The results demonstrated that extracts of paeony and licorice roots inhibit contraction of skeletal muscles in rats. Taken together, we suggest that administration of Shakuyaku-kanzo-to is a safe, effective treatment for preventing muscle cramps in patients undergoing HD.