Publications by authors named "Bjarte Havik"

Annexins are a family of calcium-dependent phospholipid-binding proteins involved in crucial cellular processes such as cell division, calcium signaling, vesicle trafficking, membrane repair, and apoptosis. In addition to these properties, Annexins have also been shown to bind RNA, although this function is not universally recognized. In the attempt to clarify this important issue, we employed an integrated combination of experimental and computational approaches.

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Article Synopsis
  • Complement proteins play a key role in eliminating synapses during brain development, but the regulation of these proteins is not well understood, particularly with regard to the protein CSMD1.
  • This study used various techniques to explore the presence and function of CSMD1 in the brain, including its interaction with complement proteins and its impact on synapse elimination in models like Csmd1-knockout mice and human-derived neurons.
  • The findings indicate that CSMD1 is crucial for regulating complement-mediated synapse elimination: its absence leads to increased complement levels, fewer synapses, and heightened microglial activity, suggesting it plays a significant role in neurodevelopmental processes such as visual circuit refinement.
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Recent meta-analyses of schizophrenia genome-wide association studies (GWASs) have identified the CUB and SUSHI multiple domains 1 (CSMD1) gene as a statistically strong risk factor. CSMD1 is a complement control-related protein suggested to inhibit the classical complement pathway, being expressed in developing neurons. However, expression of CSMD1 is largely uncharacterized and relevance for behavioral phenotypes is not previously demonstrated.

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Doublecortin-like (DCL) is a microtubule-binding protein crucial for neuroblastoma (NB) cell proliferation. We have investigated whether the anti-proliferative effect of DCL knockdown is linked to reduced mitochondrial activity. We found a delay in tumor development after DCL knockdown in vivo in doxycycline-inducible NB tumor xenografts.

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Background: The neocortex is a highly specialised and complex brain structure, involved in numerous tasks, ranging from processing and interpretation of somatosensory information, to control of motor functions. The normal function linked to distinct neocortical areas might involve control of highly specific gene expression, and in order to identify such regionally enriched genes, we previously analysed the global gene expression in three different cortical regions (frontomedial, temporal and occipital cortex) from the adult rat brain. We identified distinct sets of differentially expressed genes.

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We have characterized the expression of doublecortin-like (DCL), a microtubule-associated protein involved in embryonic neurogenesis that is highly homologous to doublecortin (DCX), in the adult mouse brain. To this end, we developed a DCL-specific antibody and used this to compare DCL expression with DCX. In the neurogenic regions of the adult brain like the subventricular zone (SVZ), the rostral migratory stream (RMS), the olfactory bulb (OB), and the hippocampus, DCL colocalizes with DCX in immature neuronal cell populations.

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Doublecortin and calmodulin like kinase 1 (DCLK1) is implicated in synaptic plasticity and neurodevelopment. Genetic variants in DCLK1 are associated with cognitive traits, specifically verbal memory and general cognition. We investigated the role of DCLK1 variants in three psychiatric disorders that have neuro-cognitive dysfunctions: schizophrenia (SCZ), bipolar affective disorder (BP) and attention deficit/hyperactivity disorder (ADHD).

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Background: Familial diarrhea disorders are, in most cases, severe and caused by recessive mutations. We describe the cause of a novel dominant disease in 32 members of a Norwegian family. The affected members have chronic diarrhea that is of early onset, is relatively mild, and is associated with increased susceptibility to inflammatory bowel disease, small-bowel obstruction, and esophagitis.

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Background: Patients with schizophrenia often suffer from cognitive dysfunction, including impaired learning and memory. We recently demonstrated that long-term potentiation in rat hippocampus, a mechanistic model of learning and memory, is linked to gene expression changes in immunity-related processes involved in complement activity and antigen presentation. We therefore aimed to examine whether key regulators of these processes are genetic susceptibility factors in schizophrenia.

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Bipolar disorder has been associated with disturbances in circadian rhythms. Lithium is frequently used in the long-term treatment of bipolar disorder, and has been shown to prolong such rhythms in animals and humans. To examine whether lithium affects the expression of genes regulating the circadian clock, cultured NIH-3T3 cells were synchronized by serum-shocking, and the relative expression of the clock genes Period1 (Per1), Period2 (Per2), Period3 (Per3), Cryptochrome1 (Cry1), Cryptochrome2 (Cry2), Brain and muscle aryl hydrocarbon nuclear translocator-like 1 (Bmal1), Circadian locomotor output cycles kaput (Clock), Rev-Erb-α (Nr1d1), RAR-related orphan receptor α (Ror-α), Glycogen synthase kinase-3β (Gsk-3β), Casein kinase 1-ε (CK1-ε; Csnk1ε), E4 binding protein 4 (E4BP4; Nfil-3) and albumin D-binding protein (Dbp) was examined for three consecutive days in the presence of lithium (20 mM) or vehicle (20 mM NaCl).

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Background: Human memory and general cognitive abilities are complex functions of high heritability and wide variability in the population. The brain-derived neurotrophic factor (BDNF) plays an important role in mammalian memory formation.

Methodology / Principal Finding: Based on the identification of genes markedly up-regulated during BDNF-induced synaptic consolidation in the hippocampus, we selected genetic variants that were tested in three independent samples, from Norway and Scotland, of adult individuals examined for cognitive abilities.

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Background: Several antipsychotic drugs (APDs) have high propensity to induce weight gain and dyslipidemia in patients, with clozapine and olanzapine as the most potent drugs. These lipid-related effects have been attributed to drug-mediated blockade or antagonism of histamine H1 and serotonin 5-HT2 receptors as well as activation of hypothalamic AMP-activated protein kinase. We recently showed that APDs activate lipid biosynthesis in cultured liver cells through stimulation of the sterol regulatory element-binding protein (SREBP) transcription factors.

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Hsp70 is an anti-apoptotic protein over-expressed in breast, lung, rectum, endometrial and bladder cancers. In this study, we investigated the impact of Hsp70 protein expression, and its close family member, Hsc70, on breast cancer cell viability and on the activity of the Hsp90/Hsp70 chaperone complex, a complex whose activity is important for the survival of cancer cells and tumours. The simultaneous blockade of Hsp70, Hsc70 and Hsp90 was most efficient in reducing breast cancer cell viability, as compared to their respective separate blockades.

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Protein synthesis underlying activity-dependent synaptic plasticity is controlled at the level of mRNA translation. We examined the dynamics and spatial regulation of two key translation factors, eukaryotic initiation factor 4E (eIF4E) and elongation factor-2 (eEF2), during long-term potentiation (LTP) induced by local infusion of brain-derived neurotrophic factor (BDNF) into the dentate gyrus of anesthetized rats. BDNF-induced LTP led to rapid, transient phosphorylation of eIF4E and eEF2, and enhanced expression of eIF4E protein in dentate gyrus homogenates.

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Background: The etiology of schizophrenia is unknown, but neurodevelopmental disturbances, myelin- and oligodendrocyte abnormalities and synaptic dysfunction have been suggested as pathophysiological factors in this severe psychiatric disorder. Cholesterol is an essential component of myelin and has proved important for synapse formation. Recently, we demonstrated that the antipsychotic drugs clozapine and haloperidol stimulate lipogenic gene expression in cultured glioma cells through activation of the sterol regulatory element-binding protein (SREBP) transcription factors.

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Brain-derived neurotrophic factor (BDNF) is a critical regulator of transcription-dependent adaptive neuronal responses, such as long-term potentiation (LTP). Brief infusion of BDNF into the dentate gyrus of adult anesthetized rats triggers stable LTP at medial perforant path-granule synapses that is transcription-dependent and requires induction of the immediate early gene Arc. Rather than acting alone, Arc is likely to be part of a larger BDNF-induced transcriptional program.

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Messenger ribonucleic acid encoding the alpha-subunit of calcium/calmodulin-dependent protein kinase II (camkII) is abundantly and constitutively expressed in dendrites of pyramidal and granule cell neurons of the adult hippocampus. Recent evidence suggests that camkII messenger ribonucleic acid is stored in a translationally dormant state within ribonucleic acid storage granules. Delivery of camkII messenger ribonucleic acid from sites of storage to sites of translation may therefore be a key step in activity-driven dendritic protein synthesis and synaptic plasticity.

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