Doublecortin marks a new population of transiently amplifying muscle progenitor cells and is required for myofiber maturation during skeletal muscle regeneration.

Muscle satellite cells are indispensable for muscle regeneration, but the functional diversity of their daughter cells is unknown. Here, we show that many Pax7(+)MyoD(-) cells locate both beneath and outside the basal lamina during myofiber maturation. A large majority of these Pax7(+)MyoD(-) cells are not self-renewed satellite cells, but have different potentials for both proliferation and differentiation from Pax7(+)MyoD(+) myoblasts (classical daughter cells), and are specifically marked by expression of the doublecortin (Dcx) gene. Transplantation and lineage-tracing experiments demonstrated that Dcx-expressing cells originate from quiescent satellite cells and that the microenvironment induces Dcx in myoblasts. Expression of Dcx seems to be necessary for myofiber maturation because Dcx-deficient mice exhibited impaired myofiber maturation resulting from a decrease in the number of myonuclei. Furthermore, in vitro and in vivo studies suggest that one function of Dcx in myogenic cells is acceleration of cell motility. These results indicate that Dcx is a new marker for the Pax7(+)MyoD(-) subpopulation, which contributes to myofiber maturation during muscle regeneration.

CDKL5 controls postsynaptic localization of GluN2B-containing NMDA receptors in the hippocampus and regulates seizure susceptibility.

Mutations in the Cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders accompanied by intractable epilepsies, i.e. West syndrome or atypical Rett syndrome. Here we report generation of the Cdkl5 knockout mouse and show that CDKL5 controls postsynaptic localization of GluN2B-containing N-methyl-d-aspartate (NMDA) receptors in the hippocampus and regulates seizure susceptibility. Cdkl5 -/Y mice showed normal sensitivity to kainic acid; however, they displayed significant hyperexcitability to NMDA. In concordance with this result, electrophysiological analysis in the hippocampal CA1 region disclosed an increased ratio of NMDA/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated excitatory postsynaptic currents (EPSCs) and a significantly larger decay time constant of NMDA receptor-mediated EPSCs (NMDA-EPSCs) as well as a stronger inhibition of the NMDA-EPSCs by the GluN2B-selective antagonist ifenprodil in Cdkl5 -/Y mice. Subcellular fractionation of the hippocampus from Cdkl5 -/Y mice revealed a significant increase of GluN2B and SAP102 in the PSD (postsynaptic density)-1T fraction, without changes in the S1 (post-nuclear) fraction or mRNA transcripts, indicating an intracellular distribution shift of these proteins to the PSD. Immunoelectron microscopic analysis of the hippocampal CA1 region further confirmed postsynaptic overaccumulation of GluN2B and SAP102 in Cdkl5 -/Y mice. Furthermore, ifenprodil abrogated the NMDA-induced hyperexcitability in Cdkl5 -/Y mice, suggesting that upregulation of GluN2B accounts for the enhanced seizure susceptibility. These data indicate that CDKL5 plays an important role in controlling postsynaptic localization of the GluN2B-SAP102 complex in the hippocampus and thereby regulates seizure susceptibility, and that aberrant NMDA receptor-mediated synaptic transmission underlies the pathological mechanisms of the CDKL5 loss-of-function.

Neurophysiological and brain structural insights into cyclin-dependent kinase-like 5 deficiency disorder: Visual and auditory evoked potentials and MRI analysis.

OBJECTIVE: CDKL5 deficiency disorder (CDD), an epileptic encephalopathy for which novel therapeutics are under development, lacks valid and reliable measures of therapeutic efficacy. We aimed to elucidate the neurophysiological and brain structural features of CDD patients and identify objective indicators reflecting the clinical severity. METHODS: Twelve CDD patients and 12 healthy controls (HCs) participated. The clinical severity of CDD was scored using the CDD severity assessment (CDD-SA). The participants underwent visual evoked potential (VEP), auditory brainstem response (ABR), structural MRI, and diffusion tensor imaging (DTI) analyses. Measurements from each modality were compared with normal values of age-matched cohorts (VEP and ABR) or statistically compared between CDD patients and HCs (MRI). RESULTS: VEP showed a significant correlation between P100 latency and CDD-SA in CDD patients. ABR showed abnormalities in six patients (50%), including prolonged V-wave latency (n = 2), prolonged inter-peak latency between waves I and V (n = 3), and mild hearing loss (n = 4). Structural MRI showed a significant reduction in cortical volume in the left pars triangularis and right cerebellum compared with HCs. DTI showed a widespread decrease in fractional anisotropy and an increase in mean and radial diffusivity compared with HCs. CONCLUSION: CDD patients had reduced cortical volume in the left pars triangularis, a brain region crucial for speech, and one-third of patients had mild hearing loss. These changes may be involved in language impairments in CDD patients. Additionally, P100 latency significantly correlated with the clinical severity. These features can be used to assess the clinical severity of CDD.

CDKL5 deficiency causes epileptic seizures independent of cellular mosaicism.

OBJECTIVE: In a study using a mouse model of CDKL5 deficiency disorder (CDD), seizures are specific to female mice heterozygous for Cdkl5 mutations and not observed in hemizygous knockout males or homozygous knockout females. The aim of this study was to examine whether the clinical phenotype of patients with CDD can be impacted by the type of genetic variant. METHODS: Eleven CDD patients (six females and five males) were included in this study. The molecular diagnosis of hemizygous male patients was performed using digital PCR and their clinical phenotypes were compared with those of patients with mosaic or heterozygous CDKL5 variants. The severity of clinical phenotypes was graded by using CDKL5 Developmental Score and the adapted version of the CDKL5 Clinical Severity Assessment. The effect of cellular mosaicism on the severity of CDD was studied by comparing the clinical characteristics and comorbidities between individuals with hemizygous and mosaic or heterozygous CDKL5 variants. RESULTS: One of the five male patients was mosaic for the CDKL5 variant. All patients developed seizures irrespective of their genetic status of the pathogenic variant. However, cellular mosaicism of CDKL5 deficiency was associated with lesser severity of other comorbidities such as feeding, respiratory, and visual functional impairments. SIGNIFICANCE: This study provided evidence that cellular mosaicism of CDKL5 deficiency was not necessarily required for developing epilepsy. CDD patients not only exhibited clinical features of epilepsy but also exhibited the developmental consequences arising directly from the effect of the CDKL5 pathogenic variant.

RANBP2 mutation causing autosomal dominant acute necrotizing encephalopathy attenuates its interaction with COX11.

PURPOSE: Autosomal dominant acute necrotizing encephalopathy (ADANE) is caused by missense mutations in the gene encoding Ran-binding protein 2 (RANBP2), a nuclear pore protein regulating mitochondrial localization and function. Previous studies have found that RANBP2 binds to COX11 and suppresses its inhibitory activity over hexokinase1. To further elucidate mitochondrial dysfunction in ADANE, we analyzed the interaction between mutated RANBP2 and COX11. METHODS: We extracted cDNA from a patient and constructed pGEX wild-type or mutant-type vectors including RANBP2 c.1754C>T, the commonest variant in ADANE. We transformed E. coli competent cells with the vectors and had them express GST-RANBP2 recombinant protein, and conducted a pull-down assay of RANBP2 and COX11. RESULTS: The amount of COX11 bound to mutated RANBP2 was significantly smaller than that bound to the wild-type RANBP2. CONCLUSION: Mutated RANBP2 had an attenuated binding ability to COX11. Whether this change indeed decreases ATP production remains to be further explored.

Doublecortin-like kinase functions with doublecortin to mediate fiber tract decussation and neuronal migration.

The potential role of doublecortin (Dcx), encoding a microtubule-associated protein, in brain development has remained controversial. Humans with mutations show profound alterations in cortical lamination, whereas in mouse, RNAi-mediated knockdown but not germline knockout shows abnormal positioning of cortical neurons. Here, we report that the doublecortin-like kinase (Dclk) gene functions in a partially redundant pathway with Dcx in the formation of axonal projections across the midline and migration of cortical neurons. Dosage-dependent genetic effects were observed in both interhemispheric connectivity and migration of cortically and subcortically derived neurons. Surprisingly, RNAi-mediated knockdown of either gene results in similar migration defects. These results indicate the Dcx microtubule-associated protein family is required for proper neuronal migration and axonal wiring.

Doublecortin maintains bipolar shape and nuclear translocation during migration in the adult forebrain.

The ability of the mature mammalian nervous system to continually produce neuronal precursors is of considerable importance, as manipulation of this process might one day permit the replacement of cells lost as a result of injury or disease. In mammals, the anterior subventricular zone (SVZa) region is one of the primary sites of adult neurogenesis. Here we show that doublecortin (DCX), a widely used marker for newly generated neurons, when deleted in mice results in a severe morphological defect in the rostral migratory stream and delayed neuronal migration that is independent of direction or responsiveness to Slit chemorepulsion. DCX is required for nuclear translocation and maintenance of bipolar morphology during migration of these cells. Our data identifies a critical function for DCX in the movement of newly generated neurons in the adult brain.

[Successful treatment of a gastrointestinal stromal tumor with liver metastases in a case that tolerated imatinib administration, by radiofrequency ablation using contrast-enhanced ultrasonography].

We report a case of gastrointestinal stromal tumor (GIST) with liver metastases which was undetectable by B-mode ultrasonography, effectively treated by radiofrequency ablation using contrast-enhanced ultrasonography US. A 43-year-old woman was admitted for the treatment of 6 lesions up to 4cm in diameter, which had emerged from necrotic sites within the liver after imatinib treatment. The recurrent lesions were not detected on B-mode US, and it was difficult to perform radiofrequency ablation (RFA) treatment. Using a contrast-enhanced agent (sonazoid), the recurrent lesions were detected and treated by RFA. RFA is considered to be an effective treatment for GIST with liver metastases that tolerate imatinib administration.

Lis1 and doublecortin function with dynein to mediate coupling of the nucleus to the centrosome in neuronal migration.

Humans with mutations in either DCX or LIS1 display nearly identical neuronal migration defects, known as lissencephaly. To define subcellular mechanisms, we have combined in vitro neuronal migration assays with retroviral transduction. Overexpression of wild-type Dcx or Lis1, but not patient-related mutant versions, increased migration rates. Dcx overexpression rescued the migration defect in Lis1+/- neurons. Lis1 localized predominantly to the centrosome, and after disruption of microtubules, redistributed to the perinuclear region. Dcx outlined microtubules extending from the perinuclear "cage" to the centrosome. Lis1+/- neurons displayed increased and more variable separation between the nucleus and the preceding centrosome during migration. Dynein inhibition resulted in similar defects in both nucleus-centrosome (N-C) coupling and neuronal migration. These N-C coupling defects were rescued by Dcx overexpression, and Dcx was found to complex with dynein. These data indicate Lis1 and Dcx function with dynein to mediate N-C coupling during migration, and suggest defects in this coupling may contribute to migration defects in lissencephaly.

Cdk5 phosphorylation of doublecortin ser297 regulates its effect on neuronal migration.

Mutations in the doublecortin (DCX) gene in human or targeted disruption of the cdk5 gene in mouse lead to similar cortical lamination defects in the developing brain. Here we show that Dcx is phosphorylated by Cdk5. Dcx phosphorylation is developmentally regulated and corresponds to the timing of expression of p35, the major activating subunit for Cdk5. Mass spectrometry and Western blot analysis indicate phosphorylation at Dcx residue Ser297. Phosphorylation of Dcx lowers its affinity to microtubules in vitro, reduces its effect on polymerization, and displaces it from microtubules in cultured neurons. Mutation of Ser297 blocks the effect of Dcx on migration in a fashion similar to pharmacological inhibition of Cdk5 activity. These results suggest that Dcx phosphorylation by Cdk5 regulates its actions on migration through an effect on microtubules.

Comprehensive behavioral analysis of the Cdkl5 knockout mice revealed significant enhancement in anxiety- and fear-related behaviors and impairment in both acquisition and long-term retention of spatial reference memory.

Mutations in the Cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders. Recently we have generated Cdkl5 KO mice by targeting exon 2 on the C57BL/6N background, and demonstrated postsynaptic overaccumulation of GluN2B-containing N-methyl-D-aspartate (NMDA) receptors in the hippocampus. In the current study, we subjected the Cdkl5 KO mice to a battery of comprehensive behavioral tests, aiming to reveal the effects of loss of CDKL5 in a whole perspective of motor, emotional, social, and cognition/memory functions, and to identify its undetermined roles. The neurological screen, rotarod, hot plate, prepulse inhibition, light/dark transition, open field, elevated plus maze, Porsolt forced swim, tail suspension, one-chamber and three-chamber social interaction, 24-h home cage monitoring, contextual and cued fear conditioning, Barnes maze, and T-maze tests were applied on adult Cdkl5 -/Y and +/Y mice. Cdkl5 -/Y mice showed a mild alteration in the gait. Analyses of emotional behaviors revealed significantly enhanced anxiety-like behaviors of Cdkl5 -/Y mice. Depressive-like behaviors and social interaction of Cdkl5 -/Y mice were uniquely altered. The contextual and cued fear conditioning of Cdkl5 -/Y mice were comparable to control mice; however, Cdkl5 -/Y mice showed a significantly increased freezing time and a significantly decreased distance traveled during the pretone period in the altered context. Both acquisition and long-term retention of spatial reference memory were significantly impaired. The morphometric analysis of hippocampal CA1 pyramidal neurons revealed impaired dendritic arborization and immature spine development in Cdkl5 -/Y mice. These results indicate that CDKL5 plays significant roles in regulating emotional behaviors especially on anxiety- and fear-related responses, and in both acquisition and long-term retention of spatial reference memory, which suggests that focus and special attention should be paid to the specific mechanisms of these deficits in the CDKL5 deficiency disorder.

Expression of c-Fos protein in the brain after intravenous injection of ghrelin in rats.

In this study, we surveyed central neurons that might be activated after peripheral administration of a gut-brain peptide ghrelin, by examining neurons expressing c-Fos protein. First, we examined the relationship between the dose of ghrelin and the amount of gastric acid secreted. Ghrelin induced a significant increase in the amount of gastric acid secretion in a dose-dependent manner. Secondly, we examined central neurons that expressed c-Fos protein after intravenous injection of ghrelin. We found that intravenously injected ghrelin induced the neural expression of c-Fos protein in several nuclei and circumventricular organs in the brain. These results suggest that ghrelin released into the circulation may stimulate central neurons that have some role in the control mechanism for gastric acid secretion.

Multiple dose-dependent effects of Lis1 on cerebral cortical development.

Humans with heterozygous inactivating mutations of the Lis1 gene display type I lissencephaly, a severe form of cortical dysplasia hypothesized to result from abnormal neuronal migration. Previously we reported the construction of an allelic series of the Lis1 gene in mice to analyze the effects of graded reduction of LIS1 protein on the pathogenesis of this disorder and demonstrated a cell autonomous defect in neuronal migration (Hirotsune et al., 1998). Here we report the systematic examination of the consequences of dosage reduction of LIS1 on neocortical development using wild-type, null heterozygous (45% LIS1 protein), and compound null/hypomorphic (35% LIS1 protein) mice. The development of the preplate, Cajal-Retzius cells, and the radial glial scaffold appeared unaffected by LIS1 levels. However, a dose-dependent morphologic change in disorganization of the subplate was noted. LIS1 dose-dependent defects in neuronal migration were found in vivo and in vitro. The position and number of mitotic cells in the ventricular zone were more abnormal as LIS1 levels decreased, suggesting defects in interkinetic nuclear migration and neuroblast proliferation. LIS1 dose-dependent progressive thinning of the cortex and ventricular zone occurred by programmed cell death. Thus, in addition to its requirement for cell autonomous neuronal migration, LIS1 influences the generation and survival of cortical ventricular zone neuroblasts. These studies reveal the importance of LIS1 levels in orderly cerebral cortical morphogenesis and suggest new insights into the pathogenesis of type I lissencephaly.

Effect of interleukin-8 on histamine release from totally isolated vascularly perfused rat stomach.

BACKGROUND: Recent studies have demonstrated relationships between cytokines and gastric acid secretion. The present study was performed in rats to elucidate the effects of interleukin-8 (IL-8) on gastric acid secretion through an increase in histamine release from the stomach. METHODS: The experiments were performed in gastric lumen-perfused rats for the study of acid secretion and in totally isolated vascularly perfused rat stomach preparations for the study of histamine release. The histamine in the effluent was determined by radioimmunoassay. RESULTS: IL-8 (500 ng) significantly enhanced gastrin-stimulated acid secretion. IL-8, at a concentration of 500 ng/20 ml per 10 min, did not alter basal histamine release, but at 100 ng/20 ml and 500 ng/20 ml it dose-dependently increased gastrin-stimulated histamine release. CONCLUSIONS: IL-8 enhances gastrin-stimulated acid secretion and histamine release from the rat stomach, which may explain the enhancing effect of IL-8 on gastric acid secretion.

[A case of idiopathic torsion dystonia showing blepharospasm at the onset].

We report a 12-year-old boy with idiopathic torsion dystonia. Blepharospasm appeared at the age of 10, followed by truncal hypertonia and progressive scoliosis after 1 year. He had bizarre involuntary movement of his limbs upon waking, which was initially misinterpreted as a psychogenic reaction. Routine neurological examinations revealed no abnormality. Treatment with diazepam, bacrophen, 1-dopa, and clonazepam, led to only short time improvement of symptoms. At the age of 14, his symptoms gradually improved in natural course. At present he is 15 years old, and capable of normal daily activities. His clinical course was not typical of idiopathic torsion dystonia and very rare in children.

Microtubule dynamics in neuronal morphogenesis.

Microtubules (MTs) are essential for neuronal morphogenesis in the developing brain. The MT cytoskeleton provides physical support to shape the fine structure of neuronal processes. MT-based motors play important roles in nucleokinesis, process formation and retraction. Regulation of MT stability downstream of extracellular cues is proposed to be critical for axonogenesis. Axons and dendrites exhibit different patterns of MT organization, underlying the divergent functions of these processes. Centrosomal positioning has drawn the attention of researchers because it is a major clue to understanding neuronal MT organization. In this review, we focus on how recent advances in live imaging have revealed the dynamics of MT organization and centrosome positioning during neural development.

Doublecortin-like kinase enhances dendritic remodelling and negatively regulates synapse maturation.

Dendritic morphogenesis and formation of synapses at appropriate dendritic locations are essential for the establishment of proper neuronal connectivity. Recent imaging studies provide evidence for stabilization of dynamic distal branches of dendrites by the addition of new synapses. However, molecules involved in both dendritic growth and suppression of synapse maturation remain to be identified. Here we report two distinct functions of doublecortin-like kinases, chimeric proteins containing both a microtubule-binding domain and a kinase domain in postmitotic neurons. First, doublecortin-like kinases localize to the distal dendrites and promote their growth by enhancing microtubule bundling. Second, doublecortin-like kinases suppress maturation of synapses through multiple pathways, including reduction of PSD-95 by the kinase domain and suppression of spine structural maturation by the microtubule-binding domain. Thus, doublecortin-like kinases are critical regulators of dendritic development by means of their specific targeting to the distal dendrites, and their local control of dendritic growth and synapse maturation.

The doublecortin and doublecortin-like kinase 1 genes cooperate in murine hippocampal development.

The doublecortin (Dcx) and doublecortin-like kinase 1 (Dclk) genes are developmentally expressed neuronal microtubule-associated proteins. Humans with DCX mutations show a severe defect in hippocampal development, but targeted deletion in mouse shows only a defect in pyramidal neuron lamination. There is significant sequence overlap between Dcx and Dclk, suggesting functional redundancy. Here we show that the two genes display overlapping expression patterns in developing mouse hippocampus. Targeted deletion of Dclk shows no appreciable developmental defect in the hippocampus, but removal of both genes shows severe hippocampal lamination defects involving the entire cornu ammonis and dentate gyrus fields that mimic the human phenotype. These results suggest these genes are partially functionally redundant in the formation of the murine hippocampus.