The Role of T-Type Calcium Channel Genes in Absence Seizures

The thalamic relay neurons, reticular thalamic nucleus, and neocortical pyramidal cells form a circuit that sustains oscillatory burst firing, and is regarded as the underlying mechanism of absence seizures. T-type calcium channels play a key role in this circuit. Here, we review the role of T-type calcium channel genes in the development of absence seizures, and emphasize gain or loss of function mutations, and other variations that alter both quantity and quality of transcripts, and methylation status of isoforms of T-type calcium channel proteins might be of equal importance in understanding the pathological mechanism of absence seizures

A New Strategy for Identification of Highly Conserved microRNAs in Non-Model Insect, Spodoptera litura

The indigenous small non-coding RNAs, known as microRNAs (miRNAs), are important regulators of gene expression and many of them are evolutionarily conserved. Whether stem-loop RT-PCR, as a sensitive method, could be utilized to clone conserved miRNAs from non-model insects lacks information. Here, three miRNAs, sli-miR-14, sli-miR-2a and sli-bantam, were cloned from Spodoptera litura by stem-loop RT-PCR. Two groups of primers were designed, and one of them performed especially well and proved stable. The sequences of two highly conserved miRNAs, sli-miR-14 and sli-miR-2a were identical to those in Drosophila melanogaster. To validate the reliability of this strategy, pre-miR-14 and pre-miR-2a in S. litura as representatives were given as well; this shared high homology with those in D. melanogaster and Bombyx mori, and both mature sequences of sli-miR-14 and sli-miR-2a in their precursors shared 100% identity to the results shown by stem-loop RT-PCR. Moreover, expression patterns of these miRNAs were investigated by real-time quantitative PCR. Sli-miR-14 and sli-miR-2a could be detected successfully and their expression patterns showed similar characteristics with those in model insects, further suggesting stem-loop RT-PCR technology can be used for identification of highly conserved miRNAs in non-model insects. These results provide a simplified and efficient strategy for studying the structure and function of highly conserved miRNAs, especially some critical miRNAs in non-model insects

Pioneer Round of Translation Supplies Peptides for Major Histocompatibility Complex Class I Presentation

Cytotoxic T cells monitor MHC class I complexes on antigen presenting cells for the potential presence of any non-self peptides that could derive from viral infection or cancerous cells. Effective immune surveillance requires that MHC class I molecules display a peptide repertoire on the surface representing all cellular proteins. This ensures that foreign antigens from all sources are presented. How the peptide repertoire can be comprehensive despite the large differences in abundance and stability of individual proteins is not known. The pioneer round of translation is the first round of translation that occurs on newly spliced mRNA. It is associated with nonsense-mediated decay of mRNAs, allowing cells to detect and eliminate the aberrant mRNAs containing premature stop codons. We showed here that the peptide presentation by MHC I molecules was strongly influenced by the pioneer round of translation. Inhibition of the pioneer round of translation by knockdown of CBP80, a nuclear cap-binding protein, reduced peptide presentation by MHC class I molecules on the cell surface without affecting global protein synthesis. On the other hand, introduction of premature stop codons changed mRNA stability without affecting peptide presentation by MHC I on the cell surface. In addition, intronless mRNAs bypassing the pioneer round of translation resulted in reduced MHC I presentation on the cell surface. Furthermore, knockdown of CBP80 led to the deficiency of the cytosolic peptides delivered by the transporter associated with antigen processing (TAP) for the MHC class I pathway. Together, these findings highlight the importance of the pioneer round of translation in deriving peptides to generate a comprehensive display of virtually all endogenous proteins for the immune surveillanc

Glutamatergic axon-derived BDNF controls GABAergic synaptic differentiation in the cerebellum.

To study mechanisms that regulate the construction of inhibitory circuits, we examined the role of brain-derived neurotrophic factor (BDNF) in the assembly of GABAergic inhibitory synapses in the mouse cerebellar cortex. We show that within the cerebellum, BDNF-expressing cells are restricted to the internal granular layer (IGL), but that the BDNF protein is present within mossy fibers which originate from cells located outside of the cerebellum. In contrast to deletion of TrkB, the cognate receptor for BDNF, deletion of Bdnf from cerebellar cell bodies alone did not perturb the localization of pre- or postsynaptic constituents at the GABAergic synapses formed by Golgi cell axons on granule cell dendrites within the IGL. Instead, we found that BDNF derived from excitatory mossy fiber endings controls their differentiation. Our findings thus indicate that cerebellar BDNF is derived primarily from excitatory neurons--precerebellar nuclei/spinal cord neurons that give rise to mossy fibers--and promotes GABAergic synapse formation as a result of release from axons. Thus, within the cerebellum the preferential localization of BDNF to axons enhances the specificity through which BDNF promotes GABAergic synaptic differentiation

Glutamatergic axon-derived BDNF controls GABAergic synaptic differentiation in the cerebellum

To study mechanisms that regulate the construction of inhibitory circuits, we examined the role of brain-derived neurotrophic factor (BDNF) in the assembly of GABAergic inhibitory synapses in the mouse cerebellar cortex. We show that within the cerebellum, BDNF-expressing cells are restricted to the internal granular layer (IGL), but that the BDNF protein is present within mossy fibers which originate from cells located outside of the cerebellum. In contrast to deletion of TrkB, the cognate receptor for BDNF, deletion of Bdnf from cerebellar cell bodies alone did not perturb the localization of pre- or postsynaptic constituents at the GABAergic synapses formed by Golgi cell axons on granule cell dendrites within the IGL. Instead, we found that BDNF derived from excitatory mossy fiber endings controls their differentiation. Our findings thus indicate that cerebellar BDNF is derived primarily from excitatory neurons—precerebellar nuclei/spinal cord neurons that give rise to mossy fibers—and promotes GABAergic synapse formation as a result of release from axons. Thus, within the cerebellum the preferential localization of BDNF to axons enhances the specificity through which BDNF promotes GABAergic synaptic differentiation.MOE (Min. of Education, S’pore)Published versio

In Vitro Neurotrophic Properties and Structural Characterization of a New Polysaccharide LTC-1 from <i>Pyrola corbieri</i> Levl (Luticao)

Pyrola corbieri Levl has been used to strengthen bones and nourish the kidney (the kidney governs the bone and is beneficial to the brain) by the local Miao people in China. However, the functional components and neurotrophic activity have not been reported. A new acidic homogeneous heteropolysaccharide named LTC-1 was obtained and characterized by periodate oxidation, Smith degradation, partial acid hydrolysis, GC–MS spectrometry, methylation analysis, and Fourier transform infrared spectroscopy, and its molecular weight was 3239 Da. The content of mannuronic acid (Man A) in LTC-1 was 46%, and the neutral sugar was composed of L-rhamnose (L-Rha), L-arabinose (L-Ara), D-xylose (D-Xyl), D-mannose (D-Man), D-glucose (D-Glc) and D-galactose (D-Gal) with a molar ratio of 1.00:3.63:0.86:1.30:6.97:1.30. The main chain of LTC-1 was composed of Glc, Gal, Man, Man A and the branched chain Ara, Glc, Gal. The terminal residues were composed of Glc and Gal. The main chain and branched chains were linked by (1→5)-linked-Ara, (1→3)-linked-Glc, (1→4)-linked-Glc, (1→6)-linked-Glc, (1→3)-linked-Gal, (1→6)-linked-Gal, (1→3, 6)-linked-Man and ManA. Meanwhile, neurotrophic activity was evaluated through PC12 and primary hippocampal neuronal cell models. LTC-1 exhibited neurotrophic activity in a concentration-dependent manner, which significantly induced the differentiation of PC12 cells, promoted the neurite outgrowth of PC12 cells, enhanced the formation of the web architecture of dendrites, and increased the density of dendritic spines in hippocampal neurons and the expression of PSD-95. These results displayed significant neurotrophic factor-like activity of LTC-1, which suggests that LTC-1 is a potential treatment option for neurodegenerative diseases