Molecular Brain Research最新文献

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DG) to produce phosphatidic acid (PA) and is, therefore, a potential terminator of DG signaling. DG and PA are important intracellular second messengers. DG directly binds protein kinase C (PKC) then activates this multifunctional enzyme. Ca²⁺-dependent and brain-specific DGKs, α, β, and γ, are suggested to play pivotal roles in the central nervous system. To elucidate the DGK function in neuronal development, we studied the developmental changes of DGKα, β, and γ in the postnatal rat brain. By immunoblot analysis, DGKα and γ subtypes were present at birth and then gradually increased, while DGKβ was not present at birth or postnatal day 3, then increased rapidly from day 14 to reach maximum at day 28. Immunohistochemically, DGKβ and γ were distributed in different brain regions. In most brain regions, DGKγ showed sustained expression throughout the postnatal developmental periods. Interestingly, a temporal expression of DGKγ was observed in the medial geniculate nucleus during day 3 to 14, and a delay of DGKγ expression was seen in Purkinje cells, which was coincident with dendritic growth of Purkinje cells. In the hippocampal pyramidal cell, both DGKβ and γ were abundant but subcellular localization was different. DGKγ localized in the cytosol while DGKβ localized along the membrane structure. These findings suggest that each DGK subtype has a spatio-temporally different function in the developmental neurons.

Nogo is a myelin-associated protein associated with neurite outgrowth and regeneration. A previous study has reported an association between an insertion/deletion polymorphism in schizophrenia. We tested for the distribution of the polymorphism and haplotypes of this and another insertion/deletion polymorphism in our population. We have also developed an assay combining allele-specific polymerase chain reaction (AS-PCR) and restriction fragment length polymorphism (RFLP) to simultaneously type these two insertion/deletion polymorphisms. There was a statistically significant difference at the allelic level for both the CAA (χ² = 4.378, df = 1, P value = 0.036) and TATC (χ² = 5.807, df = 1, P = 0.016) polymorphisms in the female subgroup, but not in males. With our genotyping method, we also determined the molecular haplotype. Within the female gender, odds ratio is at 1.57 (95% CI 1.05–2.37) for CAACAA-TATC and 1.40 (95% CI 0.55–3.60) for CAA-TATC, the two at-risk haplotypes. Odds ratio is 0.63 (95% CI 0.42–0.93) for the protective wildtype haplotype CAA-TATCTATC. Further study of these two polymorphisms to investigate functional significance and confirm gender-specific association should be carried out.

In rodent pineal glands, sympathetic innervation, which leads to norepinephrine release, is a key process in the circadian regulation of physiology and certain gene expressions. It has been shown that gene expression of the rate-limiting enzyme in the melatonin synthesis arylalkylamine N-acetyltransferase (Aa-Nat), circadian clock gene Period1, and mitogen-activated protein kinase (MAPK) phosphtase-1 (MKP-1), is controlled mainly by a norepinephrine-beta-adrenergic receptor-cAMP signaling cascade in the rat pineal gland. To further dissect the signaling cascades that regulate those gene expressions, we examined whether MAPKs are involved in cAMP-induced gene expression. Western blot and immunohistochemical analyses showed that one of the three MAPKs, c-Jun N-terminal kinase (JNK), was expressed in the pineal, and was phosphorylated by cAMP analogue stimulation with a peak 20 min after start of the stimulation, in vitro. A specific JNK inhibitor SP600125 (Anthra[1,9-cd]pyrazol-6(2H)-one1,9-pyrazoloanthrone), but not its negative control (N¹-Methyl-1,9-pyrazoloanthrone), significantly reduced cAMP-stimulated Aa-Nat, Period1, and MKP-1 mRNA levels. Although another MAPK, p38^MAPK, has also been shown to be activated by cAMP stimulation, a p38^MAPK inhibitor, SB203580 (4-(4-Fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole, HCl), showed no effect on cAMP-induced Aa-Nat and Period1 mRNA levels; whereas SB203580, but not its negative analogue SB202474 (4-Ethyl-2(p-methoxyphenyl)-5-(4′-pyridyl)-IH-imidazole, DiHCl), significantly reduced cAMP-induced MKP-1 mRNA levels. Taken together, our data suggest that cAMP-induced Aa-Nat and Period1 are likely to be mediated by activation of JNK, whereas MKP-1 may be mediated by both p38^MAPK and JNK activations.

The CA1 region of the rat hippocampus exhibits both α and β adrenergic receptor (AR) responses, however, the specific AR subtypes involved and the neuronal expression patterns for these receptors are not well understood. We have employed single cell real time RT-PCR in conjunction with cell-specific immunohistochemical markers to determine the AR expression patterns for hippocampal neurons located in CA1, a region often implicated in learning and memory processes. Cytoplasmic samples were taken from 55 individual cells located in stratum oriens, pyramidale, or radiatum and reverse transcribed. All successfully amplified pyramidal neuron samples (n = 17) expressed mRNA for the β₂AR, with four cells additionally expressing mRNA for the β₁AR subtype. Positive interneurons from stratum oriens (n = 10) and stratum radiatum (n = 8) expressed mRNA for the α_1A and/or α_1BAR (n = 9/18) only when coexpressing transcripts for somatostatin. Interneurons containing neuropeptide Y or cholecystokinin (n = 9/18) were not positive for any of the nine AR subtypes, suggesting that CA1 interneuron AR expression is limited to a subset of somatostatin-positive cells. These findings suggest that only a select number of AR subtypes are transcriptionally expressed in CA1 and that these receptors are selective to specific neuronal cell types.

F3/contactin is a neural adhesion molecule implicated in various physiological processes. In rat brain tissues, we cloned various mRNA with the same coding region but differing in 3′ and 5′UTR. The 3′UTR presents two polyadenylation signals. At the 5′ end, we identified two leader exons, multiple transcription initiation sites and splicing events, leading to at least 19 different 5′UTR. The F3/contactin rat gene differs from the mouse gene for two reasons: (1) it contains two additional untranslated exons that are alternatively spliced and (2) it lacks the homologue mouse untranslated exon 0.

Distribution kinetics of ¹⁸F-fluoro-dihydroxy phenylalanine (¹⁸F-DOPA) were studied with high-resolution micro-positron emission tomography (microPET) imaging and conventional methods in control wild-type mice, heterozygous weaver mutant mice, and homozygous weaver mutant mice. ¹⁸F-DOPA uptake was significantly increased in the CNS within 60 min in all the genotypes examined. Homozygous weaver mutant mice exhibited significantly reduced ¹⁸F-DOPA uptake in the region of interest (striatum) as compared to heterozygous weaver mutant mice and control wild-type mice. ¹⁸F-DOPA was de-localized in the kidneys of homozygous weaver mutant mice. The radioactivity was localized primarily in the liver and kidneys within 2 h and in the urinary bladder within 4 h. After 8 h, it could be detected neither by conventional nor by microPET imaging. Distribution kinetics of ¹⁸F-DOPA with microPET imaging correlated and confirmed the conventional observations. These data are interpreted to suggest that microPET imaging may provide an efficient, noninvasive, cost-effective procedure to study distribution kinetics of PET radiopharmaceuticals in rare genetically altered animals. Furthermore, this unique and noninvasive approach may expedite quality control and drug development for human applications.

We describe the structure of the rat importin 9 gene, together with its transcripts and the encoded protein with its putative functional domains. The importin 9 gene contains 24 exons in a genomic region spanning >52,000 bp. It is transcribed into two mRNAs, generated by means of alternative polyadenylation site usage arranged in tandem. Both transcripts possess the same noncanonical polyadenylation signal (AGUAAA) in rat, this hexamer being conserved in all vertebrates examined. Additionally, intron 8 is bordered by AT–AC dinucleotides. Importin 9 is expressed throughout adult rat tissues, but the 114-kDa Importin 9 protein was detected only in the brain. The localization of the Importin 9 protein was examined by immunohistochemistry in both adult rat tissues and primary hippocampal cell cultures. The strongest labeling was detected in vivo in areas populated by neurons in high density and also in the dendritic processes emanating from these cells. This protein was clearly concentrated in the nuclei of these cells, although their cytoplasms too were heavily labeled. Strong cytoplasmic and very strong nuclear staining was found in a vast majority of the cells with neuronal morphology in vitro. Cultured cells with glial morphology generally exhibited a weaker cytoplasmic labeling. In these cells, the signal decorated the nuclear envelope without nuclear staining and gradually dwindled toward the cell periphery. These results hint at the cell- or tissue-type specific functions of this type of importin protein.

Long-term facilitation (LTF) in Aplysia is achieved by the modulation of presynaptic release. However, the underlying mechanism that might be related with the regulation of synaptic vesicle release remains unknown. Since Rab3, a neuronal GTP-binding protein, is known to be a key regulator of synaptic vesicle fusion, we investigated the involvement of Rab3 in LTF. To address this issue, we examined the effect of overexpression of wild type Aplysia Rab3 (apRab3) and its mutant forms on LTF. Overexpression of either apRab3 Q80L, a constitutively active apRab3 mutant, or wild type apRab3 completely inhibited LTF. This inhibitory role of apRab3 appears to be mediated by an interaction with an effector molecule(s), possibly Rim. Expression of apRab3 Q80L, V54E double mutant, which do not bind effector molecules such as Rim or Rabphilin, had no effect on LTF. Furthermore, expression of apRab3 Q80L, F18L, D19E triple mutant, which has reduced binding activity with Rim but normally binds with Rabphilin, enhanced evoked basal synaptic release, and the increase in synaptic strength occluded LTF. In conclusion, our data suggest that apRab3 may act as a negative clamp of LTF through the interaction with effector protein(s), possibly Rim.

Recent genetic linkage studies have identified an association between missense variations in the gene encoding the Kir4.1 potassium channel (KCNJ10) and seizure susceptibility phenotypes in both humans and mice. The results of this study demonstrate that these variations (T262S and R271C) do not produce any observable changes in channel function or in predicted channel structure. It is therefore unlikely that the seizure susceptibility phenotypes associated with these missense variations are caused by changes in the intrinsic functional properties of Kir4.1.