Astrocytic Gap Junctions Contribute to Aberrant Neuronal Synchronization in a Mouse Model of MeCP2 Duplication Syndrome / 神经科学通报·英文版

Abnormal synchronous neuronal activity has been widely detected by brain imaging of autistic patients, but its underlying neural mechanism remains unclear. Compared with wild-type mice, our in vivo two-photon imaging showed that transgenic (Tg1) mice over-expressing human autism risk gene MeCP2 exhibited higher neuronal synchrony in the young but lower synchrony in the adult stage. Whole-cell recording of neuronal pairs in brain slices revealed that higher neuronal synchrony in young postnatal Tg1 mice was attributed mainly to more prevalent giant slow inward currents (SICs). Both in vivo and slice imaging further demonstrated more dynamic activity and higher synchrony in astrocytes from young Tg1 mice. Blocking astrocytic gap junctions markedly decreased the generation of SICs and overall cell synchrony in the Tg1 brain. Furthermore, the expression level of Cx43 protein and the coupling efficiency of astrocyte gap junctions remained unchanged in Tg1 mice. Thus, astrocytic gap junctions facilitate but do not act as a direct trigger for the abnormal neuronal synchrony in young Tg1 mice, revealing the potential role of the astrocyte network in the pathogenesis of MeCP2 duplication syndrome.

Axonal cytomechanics in neuronal development

For more than a century, mechanical forces have been predicted to govern many biological processes duringdevelopment, both at the cellular level and in tissue homeostasis. The cytomechanics of the thin and highlyextended neuronal axons have intrigued generations of biologists and biophysicists. However, our knowledgeof the biophysics of neurite growth and development is far from complete. Due to its motile behavior and itsimportance in axonal pathfinding, the growth cone has received significant attention. A considerable amount ofinformation is now available on the spatiotemporal regulation of biochemical signaling and remodeling of thegrowth cone cytoskeleton. However, the cytoskeletal organization and dynamics in the axonal shaft werepoorly explored until recently. Driven by advances in microscopy, there has been a surge of interest in theaxonal cytoskeleton in the last few years. A major emerging area of investigation is the relationship betweenthe axonal cytoskeleton and the diverse mechanobiological responses of neurons. This review attempts tosummarize our current understanding of the axonal cytoskeleton and its critical role in governing axonalmechanics in the context of neuronal development.

Neuroprotection of progesterone on neonatal rats after sevoflurane inhalation anesthesia / 解放军医学杂志

[Abstract] Objective To investigate the neuroprotection of progesterone on neonatal rats after sevoflurane inhalation anesthesia and its mechanisms. Methods A total of 120 newborn Sprague-Dawley rats were randomly divided into three groups (n=40): blank control group (group C), sevoflurane group (group S) and progesterone plus sevoflurane group (group S+P), half male and half female in each group. The rats in group S were exposed to 3% sevoflurane for two hours on postnatal days (P) seven, eight and nine, which was used to establish the developmental sevoflurane neurotoxicity model. The rats in group C were exposed to mixture of gases (2 L/min, 2 hours a day). The rats in group S+P received a daily injection of progesterone (8 mg/kg) from P4 to P9 and then were exposed to 3% sevoflurane (2 L/min, 2 hours a day) for 3 consecutive days between P7 to P9. The apoptosis of nerve cells in the CA1 area of the hippocampus evaluated by TUNEL assays in neonatal rats. The relative expression of apoptosis protein (caspase-3) in the hippocampus determined by Western blotting. Rats in each group evaluated for the space orientation ability and the learning and memory ability by Y maze, Morris water maze and platform test 6 weeks after birth. Results Sevoflurane significantly increased the neuronal apoptosis in CA1 area of the hippocampus in the central nervous system of newborn rats and increased the expression of Caspase-3 in the hippocampus (P<0.01); progesterone significantly reduces neuronal apoptosis which induced by sevoflurane and the expression of Caspase-3 in the hippocampus (P<0.01). The results of the Y maze, Morris water maze and platform test showed that sevoflurane reduced the alternating scoring rate of rats (P<0.05), prolonged the time required to find the platform in the water maze (P<0.05) and increased the number of errors in the platform test (P<0.01). Progesterone significantly increased the alternating scoring rate of rats (P<0.05), shortened the time required to find the platform in the water maze (P<0.05) and significantly reduced the number of errors in the platform test (P<0.01). Conclusion Repeated inhalation of 3% sevoflurane in neonatal rats can cause neurotoxic damage and induce cognitive dysfunction. Progesterone may have a neuroprotective effect on the neurotoxic damage of neonatal rats induced by sevoflurane.

mA Regulates Neurogenesis and Neuronal Development by Modulating Histone Methyltransferase Ezh2 / 基因组蛋白质组与生物信息学报·英文版

N-methyladenosine (mA), catalyzed by the methyltransferase complex consisting of Mettl3 and Mettl14, is the most abundant RNA modification in mRNAs and participates in diverse biological processes. However, the roles and precise mechanisms of mA modification in regulating neuronal development and adult neurogenesis remain unclear. Here, we examined the function of Mettl3, the key component of the complex, in neuronal development and adult neurogenesis of mice. We found that the depletion of Mettl3 significantly reduced mA levels in adult neural stem cells (aNSCs) and inhibited the proliferation of aNSCs. Mettl3 depletion not only inhibited neuronal development and skewed the differentiation of aNSCs more toward glial lineage, but also affected the morphological maturation of newborn neurons in the adult brain. mA immunoprecipitation combined with deep sequencing (MeRIP-seq) revealed that mA was predominantly enriched in transcripts related to neurogenesis and neuronal development. Mechanistically, mA was present on the transcripts of histone methyltransferase Ezh2, and its reduction upon Mettl3 knockdown decreased both Ezh2 protein expression and consequent H3K27me3 levels. The defects of neurogenesis and neuronal development induced by Mettl3 depletion could be rescued by Ezh2 overexpression. Collectively, our results uncover a crosstalk between RNA and histone modifications and indicate that Mettl3-mediated mA modification plays an important role in regulating neurogenesis and neuronal development through modulating Ezh2.

The Wnt Signaling Pathway and Related Therapeutic Drugs in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a series of neurodevelopmental disorder with a large genetic component. However, the pathogenic genes and molecular mechanisms of ASD have not been clearly defined. Recent technological advancements, such as next-generation sequencing, have led to the identification of certain loci that is responsible for the pathophysiology of ASD. Three functional pathways, such as chromatin remodeling, Wnt signaling and mitochondrial dysfunction are potentially involved in ASD. In this review, we will focus on recent studies of the involvement of Wnt signaling pathway components in ASD pathophysiology and related drugs used in ASD treatment.

The structure and function of synapsins / 医学研究生学报

The synapsins are a family of neuron specific phosphoproteins associated with the membranes of synaptic vesicles. The synapsins play important roles in the neurotransmitter release and during the early neuronal development. In this review, we focus on the family members, gene location, distribution, structure and function of the synapsins.

The developmental expression of voltage dependent calcium channel alpha1 subunits (alpha1D, alpha1B, alpha1A, alpha1E) mRNA in the rat brain / 대한해부학회지

Voltage dependent calcium channels (VDCCs) mediate Ca++ influx into cells and are responsible for regulation of a variety of physiological effects. The key functional property of VDCCs are attributed to the calcium-pore forming alpha1 subunit. In this study, distribution pattern of alpha1 subunit (alpha1D, alpha1B, alpha1A, alpha1E) mRNA of VDCCs in developing and adult rat brain was investigated by in situ hybridization histochemistry. In the adult rat brain, each alpha1 subunit mRNA displayed a specific and distinct distribution pattern. alpha1D was highly expressed in the olfactory bulb, dentate gyrus, pituitary gland, pineal gland, hypothalamus, superior colliculus and cerebellum. Relatively low level of alpha1B was expressed throughout the whole brain and strong expression of alpha1A was observed in CA3 area of Ammon's horn, medial geniculate body, inferior colliculus and cerebellum. High level of alpha1E was found in the olfactory bulb, hippocampus, dentate gyrus, medial habenular nucleus and cerebellum. Moreover, alpha1B, alpha1A and alpha1E were expressed only in the nervous system but alpha1D was expressed not only in the nervous system but also in other tissues including liver, heart, lung and skeletal muscle. Generally the expression of alpha1D, alpha1A, and alpha1E subunit was observed from E14 and thereafter the intensity of labeling was gradually increased to P14 and then decreased to the adult level. But the expression of alpha1B subunit was observed from E14 and gradually increased to E20 and P0 and then decresaed. From the differential expressions of VDCC alpha1 subunits in developing and adult rat brain, it is suggested that each type of VDCCs may play a distinct roles in neural and nonneural tissues, and the VDCCs may be related with development of nervous system.