Dopamine receptor regulating factor, DRRF: a zinc finger transcription factor

STIL facilitates the development and malignant progression of triple-negative breast cancer through activation of Fanconi anemia pathway via interacting with KLF16

BACKGROUND

STIL is an important cell cycle-regulating protein specifically recruited to the mitotic centrosome to promote the replication of centrioles in dividing cells. However, the potential role of STIL in the regulation of the biological functions of triple-negative breast cancer remains still unclear.

METHODS

We screened for differentially expressed STIL in the Cancer Genome Atlas database. The expression of STIL protein in 10 pairs of breast cancer tissues and adjacent normal tissues was further assessed by western blotting. Functionally, the knockdown and overexpression of STIL have been used to explore the effects of STIL on breast cancer cell proliferation, migration, and invasion. Mechanistically, RNA-seq, dual-luciferase reporter assay, chromatin immunoprecipitation assay, mass spectrometry, immunoprecipitation assay, and DNA pull-down assay were performed.

RESULTS

Breast cancer tissues and cells have higher STIL expression than normal tissues and cells. STIL knockdown impairs breast cancer cell growth, migration, and invasion, whereas STIL overexpression accelerates these processes. STIL promotes breast cancer progression by regulating FANCD2 expression, and exploration of its molecular mechanism demonstrated that STIL interacts with KLF16 to regulate the expression of FANCD2.

CONCLUSIONS

Collectively, our findings identified STIL as a critical promoter of breast cancer progression that interacts with KLF16 to regulate Fanconi anemia pathway protein FANCD2. In summary, STIL is a potential novel biomarker and therapeutic target for breast cancer.

Transcriptional characterization of cocaine withdrawal versus extinction within nucleus accumbens

Substance use disorder is characterized by a maladaptive imbalance wherein drug seeking persists despite negative consequences or drug unavailability. This imbalance correlates with neurobiological alterations some of which are amplified during forced abstinence, thereby compromising the capacity of extinction-based approaches to prevent relapse. Cocaine use disorder (CUD) exemplifies this phenomenon in which neurobiological modifications hijack brain reward regions such as the nucleus accumbens (NAc) to manifest craving and withdrawal-like symptoms. While increasing evidence links transcriptional changes in the NAc to specific phases of addiction, genome-wide changes in gene expression during withdrawal vs. extinction (WD/Ext) have not been examined in a context- and NAc-subregion-specific manner. Here, we used cocaine self-administration (SA) in rats combined with RNA-sequencing (RNA-seq) of NAc subregions (core and shell) to transcriptionally profile the impact of experiencing withdrawal in the home cage or in the previous drug context or experiencing extinction training. As expected, home-cage withdrawal maintained drug seeking in the previous drug context, whereas extinction training reduced it. By contrast, withdrawal involving repetitive exposure to the previous drug context increased drug-seeking behavior. Bioinformatic analyses of RNA-seq data revealed gene expression patterns, networks, motifs, and biological functions specific to these behavioral conditions and NAc subregions. Comparing transcriptomic analysis of the NAc of patients with CUD highlighted conserved gene signatures, especially with rats that were repetitively exposed to the previous drug context. Collectively, these behavioral and transcriptional correlates of several withdrawal-extinction settings reveal fundamental and translational information about potential molecular mechanisms to attenuate drug-associated memories.

Kruppel-like Factors in Skeletal Physiology and Pathologies

Kruppel-like factors (KLFs) belong to a large group of zinc finger-containing transcription factors with amino acid sequences resembling the Drosophila gap gene Krüppel. Since the first report of molecular cloning of the KLF family gene, the number of KLFs has increased rapidly. Currently, 17 murine and human KLFs are known to play crucial roles in the regulation of transcription, cell proliferation, cellular differentiation, stem cell maintenance, and tissue and organ pathogenesis. Recent evidence has shown that many KLF family molecules affect skeletal cells and regulate their differentiation and function. This review summarizes the current understanding of the unique roles of each KLF in skeletal cells during normal development and skeletal pathologies.

Serum zinc, copper, zinc-to-copper ratio, and other essential elements and minerals in children with attention deficit/hyperactivity disorder (ADHD)

BACKGROUND

Essential trace elements and minerals play a significant role in neurodevelopment. Although certain studies demonstrated impaired essential trace element and mineral status in children with ADHD, the existing data are insufficient. The objective of the present study was to assess serum trace element and mineral levels in children with ADHD.

METHODS

Serum trace element and mineral levels in 68 children with ADHD and 68 neurotypical controls were assessed using ICP-MS at NexION 300D (PerkinElmer Inc., USA) equipped with ESI SC-2 DX4 autosampler (Elemental Scientific Inc., USA).

RESULTS

Serum Cr, Mg, and Zn levels in children with ADHD were 21 % (p = 0.010), 4 % (p = 0.005), and 7 % (p = 0. 001) lower as compared to the healthy controls, respectively. In turn, serum Cu/Zn values were 11 % higher than those in the control group. Age and gender had a significant impact on serum element levels in ADHD. Particularly, preschool children were characterized by significantly increased Cu (+8 %; p = 0.034), and Cu/Zn (+19 %; p < 0.001) values, whereas serum Zn (-9 %; p = 0.004) level was decreased. In primary school-aged children only 6 % (p = 0.007) lower Mg levels were observed. Both boys and girls with ADHD were characterized by 8 % (p = 0.016) lower serum Zn levels and 10 % (p = 0.049) higher Cu/Zn values when compared to neurotypical girls. Boys with ADHD also had significantly higher Cu/Zn, exceeding the respective control values by 12 % (p = 0.021), predominantly due to a 7 % (p = 0.035) decrease in serum Zn. Serum Mg levels were also found to be significantly lower than those in neurotypical children by 5 % (p = 0.007). In adjusted regression models serum Cr (β=-0.234; p = 0.009) and Cu/Zn (β = 0.245; p = 0.029) values were significantly associated with ADHD, respectively. Two-way ANOVA revealed a significant impact of ADHD on Cr, Mg, Zn, and Cu/Zn, whereas age was associated with Cu, I, Mg, Mo, and Cu/Zn, whereas gender accounted only for variability in serum Mn levels. Principal component analysis (PCA) also revealed significant contributions of Mg, Zn, and Cu/Zn values to ADHD variability.

CONCLUSIONS

Hypothetically, the observed decrease of essential trace elements, namely Mg and Zn, and elevation of Cu/Zn may significantly contribute to the risk of ADHD or its severity and/or comorbidity.

KLF16 Affects the MYC Signature and Tumor Growth in Prostate Cancer

Background

KLF16, a member of the Kruppel-like factor (KLF) family, functions in the regulation of dopaminergic transmission, metabolism, and endocrinology. However, the role of KLF16 in prostate cancer (PCa) remains unknown.

Methods

We screened the expression of KLFs in PCa based on bioinformatics analysis. The protein levels of KLF16 in PCa specimens were confirmed by immunohistochemistry. Inhibiting KLF16 by RNA interference with shRNA was used to determine the effects of KLF16 on PCa cell growth in vitro and in vivo. RNA sequencing was used to investigate the signaling regulated by KLF16 in PCa. Bioinformatics analysis was also used to determine the possible correlations of KLF16 and signaling in PCa cohorts.

Results

Bioinformatics analysis showed that KLF16 may be required for PCa development. Notably, the expression of KLF16 was elevated in human PCa tissues. In vitro and in vivo experiments both demonstrated that depleting KLF16 significantly inhibited the growth of PCa cells. Downregulation of KLF16 significantly decreased the expression of MYC signaling in PCa cells. Furthermore, KLF16 expression was correlated with MYC signaling activity.

Conclusion

KLF16 was overexpressed in PCa tissues compared to normal tissues. KLF16 knockdown suppressed PCa cell growth in vitro and in vivo, and a deficiency of KLF16 inhibited activation of MYC signaling.

Dopamine D1 Receptor (D1R) Expression Is Controlled by a Transcriptional Repressor Complex Containing DISC1

Disrupted-in-Schizophrenia 1 (DISC1) is a scaffold protein implicated in various psychiatric diseases. Dysregulation of the dopamine system has been associated with DISC1 deficiency, while the molecular mechanism is unclear. In this study, we propose a novel molecular mechanism underlying the transcriptional regulation of the dopamine D1 receptor (D1R) in the striatum via DISC1. We verified the increase in D1R at the transcriptional level in the striatum of DISC1-deficient mouse models and altered histone acetylation status at the D1r locus. We identified a functional interaction between DISC1 and Krüppel-like factor 16 (KLF16). KLF16 translocates DISC1 into the nucleus and forms a regulatory complex by recruiting SIN3A corepressor complexes to the D1r locus. Moreover, DISC1-deficient mice have altered D1R-mediated signaling in the striatum and exhibit hyperlocomotion in response to cocaine; the blockade of D1R suppresses these effects. Taken together, our results suggest that nuclear DISC1 plays a critical role in the transcriptional regulation of D1R in the striatal neuron, providing a mechanistic link between DISC1 and dopamine-related psychiatric symptoms.

Preferential modulation of the lateral habenula activity by serotonin-2A rather than -2C receptors: Electrophysiological and neuroanatomical evidence

AIMS

Serotonergic (5-HT) modulation of the lateral habenula (LHb) activity is central in normal and pathologic conditions such as mood disorders. Among the multiple 5-HT receptors (5-HTRs) involved, the 5-HT_2C R seems to play a pivotal role. Yet, the role of 5-HT_2A Rs in the control of the LHb neuronal activity is completely unknown.

METHODS

Single-cell extracellular recording of the LHb neurons was used in rats to study the effect of the general activation and blockade of the 5-HT_2C R and 5-HT_2A R with Ro 60-0175 and SB242084, TCB-2 and MDL11939, respectively. The expression of both receptors in the LHb was confirmed using immunohistochemistry.

RESULTS

Cumulative doses (5-640 μg/kg, iv) of Ro 60-0175 and TCB-2 affected the activity of 34% and 63% of the LHb recorded neurons, respectively. LHb neurons were either inhibited at low doses or excited at higher doses of the 5-HT_2A/C R agonists. SB242084 or MDL11939 (both at 200 μg/kg, iv) did not modify neuronal firing when injected alone, but reverted the bidirectional effects of Ro 60-0175 or TCB-2, respectively. 5-HT_2C Rs and 5-HT_2A Rs are expressed in less than the 20% of the LHb neurons, and they neither colocalize nor make heterodimers. Strikingly, only 5-HT_2A Rs are expressed by the majority of LHb astrocyte cells.

CONCLUSIONS

Peripheral administration of 5-HT_2A R agonist promotes a heterogeneous pattern of neuronal responses in the LHb, and these effects are more prominent than those induced by the 5-HT_2C R activation.

Krüppel-like factors in mammalian stem cells and development

Krüppel-like factors (KLFs) are a family of zinc-finger transcription factors that are found in many species. Recent studies have shown that KLFs play a fundamental role in regulating diverse biological processes such as cell proliferation, differentiation, development and regeneration. Of note, several KLFs are also crucial for maintaining pluripotency and, hence, have been linked to reprogramming and regenerative medicine approaches. Here, we review the crucial functions of KLFs in mammalian embryogenesis, stem cell biology and regeneration, as revealed by studies of animal models. We also highlight how KLFs have been implicated in human diseases and outline potential avenues for future research.

Novel Roles and Mechanism for Krüppel-like Factor 16 (KLF16) Regulation of Neurite Outgrowth and Ephrin Receptor A5 (EphA5) Expression in Retinal Ganglion Cells

Regenerative medicine holds great promise for the treatment of degenerative retinal disorders. Krüppel-like factors (KLFs) are transcription factors that have recently emerged as key tools in regenerative medicine because some of them can function as epigenetic reprogrammers in stem cell biology. Here, we show that KLF16, one of the least understood members of this family, is a POU4F2 independent transcription factor in retinal ganglion cells (RGCs) as early as embryonic day 15. When overexpressed, KLF16 inhibits RGC neurite outgrowth and enhances RGC growth cone collapse in response to exogenous ephrinA5 ligands. Ephrin/EPH signaling regulates RGC connectivity. The EphA5 promoter contains multiple GC- and GT-rich KLF-binding sites, which, as shown by ChIP-assays, bind KLF16 in vivo In electrophoretic mobility shift assays, KLF16 binds specifically to a single KLF site near the EphA5 transcription start site that is required for KLF16 transactivation. Interestingly, methylation of only six of 98 CpG dinucleotides within the EphA5 promoter blocks its transactivation by KLF16 but enables transactivation by KLF2 and KLF15. These data demonstrate a role for KLF16 in regulation of RGC neurite outgrowth and as a methylation-sensitive transcriptional regulator of EphA5 expression. Together, these data identify differential low level methylation as a novel mechanism for regulating KLF16-mediated EphA5 expression across the retina. Because of the critical role of ephrin/EPH signaling in patterning RGC connectivity, understanding the role of KLFs in regulating neurite outgrowth and Eph receptor expression will be vital for successful restoration of functional vision through optic nerve regenerative therapies.

Lead neurotoxicity: exploring the potential impact of lead substitution in zinc-finger proteins on mental health

This critical review focuses on one possible link between the cellular biology of lead and its neurotoxic effects: the link between Pb²⁺substitution for Zn²⁺in zinc-finger proteins and mental illness in adulthood.

Abuse potential and adverse cognitive effects of mitragynine (kratom)

Mitragynine is the major psychoactive alkaloid of the plant kratom/ketum. Kratom is widely used in Southeast Asia as a recreational drug, and increasingly appears as a pure compound or a component of 'herbal high' preparations in the Western world. While mitragynine/kratom may have analgesic, muscle relaxant and anti-inflammatory effects, its addictive properties and effects on cognitive performance are unknown. We isolated mitragynine from the plant and performed a thorough investigation of its behavioural effects in rats and mice. Here we describe an addictive profile and cognitive impairments of acute and chronic mitragynine administration, which closely resembles that of morphine. Acute mitragynine has complex effects on locomotor activity. Repeated administration induces locomotor sensitization, anxiolysis and conditioned place preference, enhances expression of dopamine transporter- and dopamine receptor-regulating factor mRNA in the mesencephalon. While there was no increase in spontaneous locomotor activity during withdrawal, animals showed hypersensitivity towards small challenging doses for up to 14 days. Severe somatic withdrawal signs developed after 12 hours, and increased level of anxiety became evident after 24 hours of withdrawal. Acute mitragynine independently impaired passive avoidance learning, memory consolidation and retrieval, possibly mediated by a disruption of cortical oscillatory activity, including the suppression of low-frequency rhythms (delta and theta) in the electrocorticogram. Chronic mitragynine administration led to impaired passive avoidance and object recognition learning. Altogether, these findings provide evidence for an addiction potential with cognitive impairments for mitragynine, which suggest its classification as a harmful drug.

Sp3/REST/HDAC1/HDAC2 Complex Represses and Sp1/HIF-1/p300 Complex Activates ncx1 Gene Transcription, in Brain Ischemia and in Ischemic Brain Preconditioning, by Epigenetic Mechanism

The Na(+)-Ca(2+) exchanger 1 (NCX1) is reduced in stroke by the RE1-silencing transcription factor (REST), whereas it is increased in ischemic brain preconditioning (PC) by hypoxia-inducible factor 1 (HIF-1). Because ncx1 brain promoter (ncx1-Br) has five putative consensus sequences, named Sp1A-E, for the specificity protein (Sp) family of transcription factors (Sp1-4), we investigated the role of this family in regulating ncx1 transcription in rat cortical neurons. Here we found that Sp1 is a transcriptional activator, whereas Sp3 is a transcriptional repressor of ncx1, and that both bind ncx1-Br in a sequence-specific manner, modulating ncx1 transcription through the Sp1 sites C-E. Furthermore, by transient middle cerebral artery occlusion (tMCAO) in rats, the transcriptional repressors Sp3 and REST colocalized with the two histone-deacetylases (HDACs) HDAC1 and HDAC2 on the ncx1-Br, with a consequent hypoacetylation. Contrarily, in PC+tMCAO the transcriptional activators Sp1 and HIF-1 colocalized with histone acetyltransferase p300 on ncx1-Br with a consequent hyperacetylation. In addition, in neurons silenced with siRNA of NCX1 and subjected to oxygen and glucose deprivation (OGD) (3 h) plus reoxygenation (RX) (24 h), the neuroprotection of Class I HDAC inhibitor MS-275 was counteracted, whereas in neurons overexpressing NCX1 and subjected to ischemic preconditioning (PC+OGD/RX), the neurotoxic effect of p300 inhibitor C646 was prevented. Collectively, these results demonstrate that NCX1 expression is regulated by the Sp3/REST/HDAC1/HDAC2 complex in tMCAO and by the Sp1/HIF-1/p300 complex in PC+tMCAO and that epigenetic intervention, by modulating the acetylation of ncx1-Br, may be a strategy for the development of innovative therapeutic intervention in stroke.

DAT1 methylation changes in alcohol-dependent individuals vs. controls

INTRODUCTION

The dopaminergic system plays a crucial role in the development of alcohol dependence. Regulation of the extracellular dopamine concentration is driven by dopamine transporter. Both, the expression and function of dopamine transporter, are influenced by chronic alcohol intake. Dopamine transporter (DAT) gene is also supposed to be differentially methylated in alcohol-dependent patients than in controls.

MATERIAL AND METHODS

DNA was extracted from peripheral blood leukocytes. We analyzed the methylation status in 23 CpG islands of DAT gene promoter in alcohol dependent subjects (n = 171) and control (n = 160) group.

RESULTS

No statistical differences in the general frequency of DAT CpG islands was revealed between patients (altogether 175 methylated islands) and control subjects (170 methylated islands (p = 0.86). However it was revealed that one of analyzed positions is significantly more often methylated in control subjects than in alcohol dependent individuals (p = 0.0296).

CONCLUSION

Further subsequent studies are necessary to determine whether the methylation change of one (out of 23) CpG site results in DAT expression changes.

Extracellular signal-related kinase 2/specificity protein 1/specificity protein 3/repressor element-1 silencing transcription factor pathway is involved in Aroclor 1254-induced toxicity in SH-SY5Y neuronal cells

Polychlorinated biphenyls (PCBs) cause a wide spectrum of toxic effects in the brain through undefined mechanisms. Exposure to the PCB mixture Aroclor-1254 (A1254) increases the repressor element-1 silencing transcription factor (REST) expression, leading to neuronal death. This study sought to understand the sequence of some molecular mechanisms to determine whether A1254 could increase REST expression and the cytoprotective effect of the phorbol ester tetradecanoylphorbol acetate (TPA) on A1254-induced toxicity in SH-SY5Y cells. As shown by Western blot analysis, A1254 (10 µg/ml) downregulates extracellular signal-related kinase 2 (ERK2) phosphorylation in a time-dependent manner, thereby triggering the binding of specificity protein 1 (Sp1) and Sp3 to the REST gene promoter as revealed by chromatin immunoprecipitation analysis. This chain of events results in an increase in REST mRNA and cell death, as assessed by quantitative real-time polymerase chain reaction and dimethylthiazolyl-2-5-diphenyltetrazolium-bromide assay, respectively. Accordingly, TPA prevented both the A1254-induced decrease in ERK2 phosphorylation and the A1254-induced increase in Sp1, Sp3, and REST protein expression. After 48 hr, TPA prevented A1254-induced cell death. ERK2 overexpression counteracted the A1254-induced increase in Sp1 and Sp3 protein expression and prevented A1254-induced Sp1 and Sp3 binding to the REST gene promoter, thus counteracting the increase in REST mRNA expression induced by the toxicant. In neuroblastoma SH-SY5Y cells, ERK2/Sp1/SP3/REST is a new pathway underlying the neurotoxic effect of PCB. The ERK2/Sp1/Sp3/REST pathway, which underlies A1254-induced neuronal death, might represent a new drug signaling cascade in PCB-induced neuronal toxicity.

Striatal development involves a switch in gene expression networks, followed by a myelination event: implications for neuropsychiatric disease

Because abnormal development of striatal neurons is thought to be the part of pathology underlying major psychiatric illnesses, we studied the expression pattern of genes involved in striatal development and of genes comprising key striatal-specific pathways, during an active striatal maturation period, the first two postnatal weeks in rat. This period parallels human striatal development during the second trimester, when prenatal stress is though to lead to increased risk for neuropsychiatric disorders. To identify genes involved in this developmental process, we used subtractive hybridization, followed by quantitative real-time PCR, which allowed us to characterize the developmental expression of over 60 genes, many not previously known to play a role in neuromaturation. Of these 12 were novel transcripts, which did not match known genes, but which showed strict developmental expression and may play a role in striatal neurodevelopment. An additional 89 genes were identified as strong candidates for involvement in this neurodevelopmental process. We show that during the first two postnatal weeks in rat, an early gene expression network, still lacking key striatal-specific signaling pathways, is downregulated and replaced by a mature gene expression network, containing key striatal-specific genes including the dopamine D1 and D2 receptors, conferring to these neurons their functional identity. Therefore, before this developmental switch, striatal neurons lack many of their key phenotypic characteristics. This maturation process is followed by a striking rise in expression of myelination genes, indicating a striatal-specific myelination event. Such strictly controlled developmental program has the potential to be a point of susceptibility to disruption by external factors. Indeed, this period is known to be a susceptibility period in both humans and rats.

Glucocorticoid receptor antagonism blocks ethanol-induced place preference learning in mice and attenuates dopamine D2 receptor adaptation in the frontal cortex

The glucocorticoid receptor (GR) plays an important role in alcohol (EtOH) self-administration behaviour by its interaction with the dopaminergic (DA) system in the brain. Here we asked whether the GR is also involved in the establishment of EtOH-induced conditioned place preference (CPP) by an interaction with the DA systems in terminal projection areas. We found that the establishment of an EtOH (2 g/kg, i.p.)-induced CPP was paralleled by a decrease in frontal cortex DA D2 receptor mRNA expression, but not in local D2 gene promoter methylation rate. No effect in other brain areas, nor on DA transporter or DA receptor regulating factor mRNA was found. The GR antagonist, RU486 (20 mg/kg, i.p.) blocked the establishment of EtOH CPP and prevented DA D2 receptor adaptations. These data may suggest a role of glucocorticoid receptor mediated D2 adaptations in the establishment of the reinforcing effects of EtOH.

Multiple transcription factor families regulate axon growth and regeneration

Understanding axon regenerative failure remains a major goal in neuroscience, and reversing this failure remains a major goal for clinical neurology. Although an inhibitory central nervous system environment clearly plays a role, focus on molecular pathways within neurons has begun to yield fruitful insights. Initial steps forward investigated the receptors and signaling pathways immediately downstream of environmental cues, but recent work has also shed light on transcriptional control mechanisms that regulate intrinsic axon growth ability, presumably through whole cassettes of gene target regulation. Here we will discuss transcription factors that regulate neurite growth in vitro and in vivo, including p53, SnoN, E47, cAMP-responsive element binding protein (CREB), signal transducer and activator of transcription 3 (STAT3), nuclear factor of activated T cell (NFAT), c-Jun activating transcription factor 3 (ATF3), sex determining region Ybox containing gene 11 (Sox11), nuclear factor κ-light chain enhancer of activated B cells (NFκB), and Krüppel-like factors (KLFs). Revealing the similarities and differences among the functions of these transcription factors may further our understanding of the mechanisms of transcriptional regulation in axon growth and regeneration.

Krüppel-like factor 11 differentially couples to histone acetyltransferase and histone methyltransferase chromatin remodeling pathways to transcriptionally regulate dopamine D2 receptor in neuronal cells

The importance of Krüppel-like factor (KLF)-mediated transcriptional pathways in the biochemistry of neuronal differentiation has been recognized relatively recently. Elegant studies have revealed that KLF proteins are important regulators of two major molecular and cellular processes critical for neuronal cell differentiation: neurite formation and the expression of neurotransmitter-related genes. However, whether KLF proteins mediate these key processes in a separate or coordinated fashion remains unknown. Moreover, knowledge on the contribution of chromatin dynamics to the biochemical mechanisms utilized by these proteins to perform their function is absent. Here we report the characterization of two antagonistic, chromatin-mediated mechanisms by which KLF11, also known as TIEG2 (transforming growth factor-β-inducible early gene 2) and MODY VII (maturity onset diabetes of the young VII), regulates transcription of the fopamine D2 receptor (Drd2) gene. First, KLF11 activates transcription by binding to a distinct Sp-KLF site within the Drd2 promoter (-98 to -94) and recruiting the p300 histone acetyltransferase. Second, Drd2 transcriptional activation is partially antagonized by heterochromatin protein 1 (HP1), the code reader for histone H3 lysine 9 methylation. Interestingly, KLF11 regulates neurotransmitter receptor gene expression in differentiating neuronal cell populations without affecting neurite formation. Overall, these studies highlight histone methylation and acetylation as key biochemical mechanisms modulating KLF-mediated neurotransmitter gene transcription. These data extend our knowledge of chromatin-mediated biochemical events that maintain key phenotypic features of differentiated neuronal cells.

Krüppel-like transcription factors in the nervous system: novel players in neurite outgrowth and axon regeneration

The Krüppel-like family of transcription factors (KLFs) have been widely studied in proliferating cells, though very little is known about their role in post-mitotic cells, such as neurons. We have recently found that the KLFs play a role in regulating intrinsic axon growth ability in retinal ganglion cells (RGCs), a type of central nervous system (CNS) neuron. Previous KLF studies in other cell types suggest that there may be cell-type specific KLF expression patterns, and that their relative expression allows them to compete for binding sites, or to act redundantly to compensate for another's function. With at least 15 of 17 KLF family members expressed in neurons, it will be important for us to determine how this complex family functions to regulate the intricate gene programs of axon growth and regeneration. By further characterizing the mechanisms of the KLF family in the nervous system, we may better understand how they regulate neurite growth and axon regeneration.

Mammalian Krüppel-like factors in health and diseases

The Krüppel-like factor (KLF) family of transcription factors regulates diverse biological processes that include proliferation, differentiation, growth, development, survival, and responses to external stress. Seventeen mammalian KLFs have been identified, and numerous studies have been published that describe their basic biology and contribution to human diseases. KLF proteins have received much attention because of their involvement in the development and homeostasis of numerous organ systems. KLFs are critical regulators of physiological systems that include the cardiovascular, digestive, respiratory, hematological, and immune systems and are involved in disorders such as obesity, cardiovascular disease, cancer, and inflammatory conditions. Furthermore, KLFs play an important role in reprogramming somatic cells into induced pluripotent stem (iPS) cells and maintaining the pluripotent state of embryonic stem cells. As research on KLF proteins progresses, additional KLF functions and associations with disease are likely to be discovered. Here, we review the current knowledge of KLF proteins and describe common attributes of their biochemical and physiological functions and their pathophysiological roles.

Hypoxia-induced transcription of dopamine D3 and D4 receptors in human neuroblastoma and astrocytoma cells

Background

Dopaminergic pathways that influence mood and behaviour are severely affected in cerebral hypoxia. In contrast, hypoxia promotes the differentiation of dopaminergic neurons. In order to clarify the hypoxic sensitivity of key dopaminergic genes, we aimed to study their transcriptional regulation in the context of neuroblastoma and astrocytoma cell lines exposed to 1% hypoxia.

Results

Quantitative RT-PCR assays revealed that the transcription of both type D3 and D4 postsynaptic dopamine receptors (DRD3 and DRD4) was induced several fold upon 2-day hypoxia in a cell-specific manner, while the vascular endothelial growth factor gene was activated after 3-hr incubation in hypoxia. On the other hand, mRNA levels of type 2 dopamine receptor, dopamine transporter, monoamino oxidase and catechol-O-methyltransferase were unaltered, while those of the dopamine receptor regulating factor (DRRF) were decreased by hypoxia. Notably, 2-day hypoxia did not result in elevation of protein levels of DRD3 and DRD4.

Conclusion

In light of the relatively delayed transcriptional activation of the DRD3 and DRD4 genes, we propose that slow-reacting hypoxia sensitive transcription factors might be involved in the transactivation of DRD3 and DRD4 promoters in hypoxia.

The ART of HIV therapies: dopaminergic deficits and future treatments for HIV pediatric encephalopathy

The concerted efforts of clinicians, scientists and caregivers of HIV-infected children have led to tremendous advances in our understanding of pediatric HIV/AIDS. Antiretroviral therapy (ART; formerly known as highly active antiretroviral therapy [HAART]) has significantly extended the longevity of HIV-infected children, but there are limitations to improvements in quality of life that may persist despite therapy. ART has remarkably reduced the incidence of neurologic deficits for the majority of infected children, but some patients do not experience these benefits and children living in poorer nations, who may not have access to antiretrovirals, are particularly at risk for developing neurologic deficits. This article reviews the neurologic symptoms of pediatric HIV infection that manifest as dopaminergic disruptions and explores potential future adjuvant therapies for HIV-related neurologic disorders in children.

Transcriptional auto-regulation of the dopamine receptor regulating factor (DRRF) gene

The murine dopamine receptor regulating factor (DRRF) gene is transcribed from a TATA-less promoter that has several putative Sp1 binding sites. The present investigation identifies functional transcription factors that modulate the expression of this gene. In the D2-dopamine receptor expressing NB41A3 cells, Sp1 potently activates transcription from the DRRF promoter in pCAT-DRRF-1153/+17, while DRRF itself effectively inhibits it. Sp1 also activates this promoter in pCAT-DRRF-310/+17. In competitive co-transfection experiments, DRRF represses the transcriptional activation induced by Sp1, while Sp1 de-represses the inhibitory effect of DRRF. Deletion of the 31 bp fragment between -1153 and -1122 decreased basal transcription down to about 60%. This fragment contains a functional AP1 binding site. In addition, deletion of the 129 bp region between -901 and -772 further decreased transcription. The latter region has a functional AP2 binding site. The present observations suggest that DRRF auto-regulates its own promoter by competing with Sp1 and that both AP1 and AP2 modulate expression of this gene.

A proteomics approach for identification of single strand DNA-binding proteins involved in transcriptional regulation of mouse mu opioid receptor gene

The pharmacological actions of morphine and morphine-like drugs such as heroin are mediated primarily through the μ opioid receptor. Previously a single strand DNA element of the mouse μ opioid receptor gene (Oprm1) proximal promoter was found to be important for regulating Oprm1 in neuronal cells. To identify proteins binding to the single strand DNA element as potential regulators for Oprm1, affinity column chromatography with the single strand DNA element was performed using neuroblastoma NS20Y cells followed by two-dimensional gel electrophoresis and MALDI-TOF mass spectrometry. We identified five poly(C)-binding proteins: heterogeneous nuclear ribonucleoprotein (hnRNP) K, α-complex proteins (αCP) αCP1, αCP2, αCP2-KL, and αCP3. Binding of these proteins to the single strand DNA element of Oprm1 was sequence-specific as confirmed by supershift assays. In cotransfection studies, hnRNP K, αCP1, αCP2, and αCP2-KL activated the Oprm1 promoter activity, whereas αCP3 acted as a repressor. Ectopic expression of hnRNP K, αCP1, αCP2, and αCP2-KL also led to activation of the endogenous Oprm1 transcripts, and αCP3 repressed endogenous Oprm1 transcripts. We demonstrate novel roles as transcriptional regulators in Oprm1 regulation for hnRNP K and αCP binding to the single strand DNA element.

Two-dimensional LC-MS/MS in detection of peptides in hypothalamus of the rat subjected to hypoxic stress

A capillary 2-D LC method coupled with IT MS has been used for separation and identification of peptides in rat hypothalamus. Animals of two different age groups (8 and 50 wk) were exposed to two different rates of CO(2 )in inhaled air to investigate the influence of different hypoxia/hypercapnia levels and their stress-related factor on the peptide excretion. Peptide compounds were fractionated (strong cation exchange chromatography), trapped, and separated (RP chromatography), and MS/MS mass spectra were used for identification. About 107 peptide compounds were identified and 88 of them were semiquantified. Among the characterized peptides, there were fragments from proteins such as proenkephalin A, proSAAS, prosomatostatin, prooxytocin, vasopressin, etc. Explorative principal component analysis (PCA) combined with hypothesis testing was applied to the obtained data to investigate the impact of age and hypoxic stress factors on the peptide pattern. Twenty-six peptides revealed significant differences in concentrations between the animal groups influenced by age and influx rate.

Differential Repression by Freud-1/CC2D1A at a Polymorphic Site in the Dopamine-D2 Receptor Gene

Freud-1/CC2D1A is a transcriptional repressor of the serotonin-1A receptor gene and was recently genetically linked to non-syndromic mental retardation. To identify new Freud-1 gene targets, data base mining for Freud-1 recognition sequences was done. A highly homologous intronic element (D2-DRE) was identified in the human dopamine-D2 receptor (DRD2) gene, and the role of Freud-1 in regulating the gene at this site was assessed. Recombinant Freud-1 bound specifically to the D2-DRE, and a major protein-D2-DRE complex was identified in nuclear extracts that was supershifted using Freud-1-specific antibodies. Endogenous Freud-1 binding to the D2-DRE in cells was detected using chromatin immunoprecipitation. The D2-DRE conferred strong repressor activity in transcriptional reporter assays that was dependent on the Freud-1 recognition sequence. In three different human cell lines, the level of Freud-1 protein was inversely related to DRD2 expression. Knockdown of endogenous Freud-1 using small interfering RNA resulted in an up-regulation of DRD2 RNA and binding sites, demonstrating a crucial role for Freud-1 in DRD2 regulation. A previously uncharacterized single nucleotide A/G polymorphism (rs2734836) was located adjacent to the D2-DRE and conferred allele-specific Freud-1 binding and repression, with the major G-allele having reduced activity. These studies demonstrate a key role for Freud-1 to regulate DRD2 expression and provide the first mechanistic insights into its transcriptional regulation. Allele-specific regulation of DRD2 expression by Freud-1 may possibly associate with psychiatric disorders or mental retardation.

Identification and characterization of two nuclear factor-kappaB sites in the regulatory region of the dopamine D2 receptor

Regulation of D2 receptor (D2R) expression is crucial in the function of dopaminergic systems. Because alterations of D2R expression may contribute to the development of different disorders, it is important to elucidate the mechanisms regulating D2R gene transcription. We report the characterization of two putative nuclear factor-kappaB (NF-kappaB) motifs, referred to as D2-kappaB sites, in the human D2R promoter, and demonstrate that they bind NF-kappaB subunits and stimulate D2R promoter activity. D2-kappaB sites show different degrees of conservation and specificity, when compared with canonical kB sites. The D2-kappaB1 site (from -407 to -398) is highly conserved and binds p50/p65 and p50/c-Rel complexes, whereas D2-kappaB2 (from -513 to -504) is more degenerated and only binds p50/p65 heterodimers. Activation of D2-kappaB sites in COS-7 cells expressing a luciferase reporter vector containing the D2R promoter resulted in increased transcriptional activity. Site-directed mutagenesis of each D2-kappaB site differentially modified D2R promoter activity. In particular, mutation of the D2-kappaB1 motif did not affect D2R promoter response to p50/c-Rel complexes, whereas inactivation of the D2-kappaB2 site decreased it. Mutations of either D2-kappaB1 or D2-kappaB2 sites attenuated the D2R promoter transcriptional efficiency induced by p50/p65 complexes. Thus, D2R transcription mediated by p50/c-Rel is supported mainly by the D2-kappaB2 site, whereas both sites are necessary to support the full transcriptional activity mediated by p50/p65 complexes. A correlation was found between NF-kappaB activity and D2R expression in the pituitary and pituitary-derived cells but not in the striatum, suggesting that NF-kappaB regulation of D2R expression could be a pituitary-specific mechanism.

Striatal specificity of gene expression dysregulation in Huntington's disease

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by an expanded CAG repeat region in exon 1 of the HD gene. This mutation results in the presence of an abnormally long polyglutamine tract in the encoded protein, huntingtin (htt). A major question in this field is how the mutant htt protein, which is expressed ubiquitously throughout the brain and body, causes severe neuropathologic changes predominantly in the striatum. The mechanisms accounting for this specificity are unknown. The role of transcriptional dysregulation in the pathophysiology of HD has gained much attention in recent years, however, this theory has been unable to explain the specificity of dysfunction and degeneration in HD. Microarray studies have showed hundreds of gene expression changes in mouse models of HD and in post-mortem brain samples from HD subjects. Among the genes whose expression levels are preferentially altered are those that exhibit enriched expression in the striatum, which we have argued are the most relevant to disease pathology. These "striatal-enriched" genes are associated with several systems previously implicated in HD pathology, especially disturbances in transcriptional processes and calcium homeostasis. Large-scale changes in striatal gene expression in this manner would likely have particularly devastating effects to normal striatal function and could explain the specificity of striatal dysfunction and ultimate neurodegeneration observed in HD.

Brain-derived neurotrophic factor regulates the expression of D1 dopamine receptors

We have previously demonstrated that the CAD catecholaminergic neuronal cell line is an appropriate model system to study the regulation of D(1) dopamine receptor expression. In this report, we show that brain-derived neurotrophic factor (BDNF) up-regulates the expression of D(1) dopamine receptor in CAD cells. In addition, by comparing D(1) receptor mRNA expression in wild-type, heterozygous and homozygous trkB knockout mice, we show that TrkB receptor signaling up-regulates D(1) receptor expression in vivo. In CAD cells expressing the TrkB receptor, BDNF increased D(1) receptor mRNA in a time- and dose-dependent manner with a fourfold increase in D(1) receptor mRNA observed as early as 3 h with 10 ng/mL of BDNF. Using different classes and concentrations of kinase inhibitors, we determined that BDNF-induced increase of D(1) receptor mRNA is mediated by the phosphatidylinositol 3-kinase signaling pathway. The increase required both new transcription and protein synthesis, as it was blocked by actinomycin D and cyclohexamide, respectively. Promoter deletion analysis identified a D(1) promoter region necessary for mediating the effect of BDNF. These results provide novel evidence that D(1) dopamine receptor expression is regulated by BDNF and its signaling pathway.

Sp1 Is Up-regulated in Cellular and Transgenic Models of Huntington Disease, and Its Reduction Is Neuroprotective

Interactions between mutant huntingtin (Htt) and a variety of transcription factors including specificity proteins (Sp) have been suggested as a central mechanism in Huntington disease (HD). However, the transcriptional activity induced by Htt in neurons that triggers neuronal death has yet to be fully elucidated. In the current study, we characterized the relationship of Sp1 to Htt protein aggregation and neuronal cell death. We found increased levels of Sp1 in neuronal-like PC12 cells expressing mutant Htt, primary striatal neurons, and brain tissue of HD transgenic mice. Sp1 levels were also elevated when 3-nitropropionate (3-NP) was used to induce cell death in PC12 cells. To assess the effects of knocking down Sp1 in HD pathology, we used Sp1 siRNA, a heterozygous Sp1 knock-out mouse, and mithramycin A, a DNA-intercalating agent that inhibits Sp1 function. The three approaches consistently yielded reduced levels of Sp1 which ameliorated toxicity caused by either mutant Htt or 3-NP. In addition, when HD mice were crossed with Sp1 heterozygous knock-out mice, the resulting offspring did not experience the loss of dopamine D2 receptor mRNA characteristic of HD mice, and survived longer than their HD counterparts. Our data suggest that enhancement of transcription factor Sp1 contributes to the pathology of HD and demonstrates that its suppression is beneficial.

Induction of two cytochrome P450 genes, Cyp6a2 and Cyp6a8, of Drosophila melanogaster by caffeine in adult flies and in cell culture

To examine whether caffeine, the most widely used xenobiotic compound, would induce insect cytochrome P450 or CYP gene expression, upstream DNA fragments of Cyp6a2 (0.12, 0.26, 0.52 and 0.98-kb) and Cyp6a8 (0.06, 0.1, 0.2, 0.5 and 0.8-kb) genes of Drosophila melanogaster were individually fused to the firefly luciferase (luc) reporter gene. Promoter activities of these constructs were examined in Drosophila SL-2 cells using luciferase assays. Activity of 0.2- and 0.8-kb upstream DNA of Cyp6a8 was also measured in transgenic female flies. When these flies were treated with 2 mM pure caffeine or Vivarin caffeine, both DNA fragments showed a 4-5-fold induction of promoter activity. Endogenous Cyp6a8 and Cyp6a2 genes in these flies also showed caffeine-induced expression. In addition, both 0.2- and 0.8-kb DNAs showed differential basal and caffeine-induced activity in head, ovaries, gut, cuticle plus fat body and malpighian tubules. However, in all tissues 0.8-kb DNA always showed higher basal and caffeine-induced activities compared to the 0.2-kb DNA, suggesting that the additional DNA present in the 0.8-kb fragment has sequences that enhance both activities. In SL-2 cells, all reporter constructs of each Cyp6 gene showed significantly higher basal activity than the empty vector. Sequences that boost basal activity are located in -265/-129 and -983/-522 DNA of Cyp6a2, and -199/-109 and -491/-199 DNA of Cyp6a8 genes. While the 0.12- and 0.1-kb upstream DNAs of Cyp6a2 and Cyp6a8 genes respectively did not show caffeine-inducibility in SL-2 cells, the longest upstream DNA of each gene gave the highest level of induction. Caffeine-responsive sequences are not clustered at one place; they appear to be dispersed in -983/-126 and -761/-109 regions of Cyp6a2 and Cyp6a8 genes which also contain many binding sites for activator protein 1 (AP1) and cyclic AMP response element binding protein (CRE-BP). Significance of these binding sites in caffeine-inducibility has been discussed.

Selective deficits in the expression of striatal-enriched mRNAs in Huntington's disease

We have identified and cataloged 54 genes that exhibit predominant expression in the striatum. Our hypothesis is that such mRNA molecules are likely to encode proteins that are preferentially associated with particular physiological processes intrinsic to striatal neurons, and therefore might contribute to the regional specificity of neurodegeneration observed in striatal disorders such as Huntington's disease (HD). Expression of these genes was measured simultaneously in the striatum of HD R6/1 transgenic mice using Affymetrix oligonucleotide arrays. We found a decrease in expression of 81% of striatum-enriched genes in HD transgenic mice. Changes in expression of genes associated with G-protein signaling and calcium homeostasis were highlighted. The most striking decrement was observed for a newly identified subunit of the sodium channel, beta 4, with dramatic decreases in expression beginning at 8 weeks of age. A subset of striatal genes was tested by real-time PCR in caudate samples from human HD patients. Similar alterations in expression were observed in human HD and the R6/1 model for the striatal genes tested. Expression of 15 of the striatum-enriched genes was measured in 6-hydroxydopamine-lesioned rats to determine their dependence on dopamine innervation. No changes in expression were observed for any of these genes. These findings demonstrate that mutant huntingtin protein causes selective deficits in the expression of mRNAs responsible for striatum-specific physiology and these may contribute to the regional specificity of degeneration observed in HD.

The polymorphic nature of the human dopamine D4 receptor gene: a comparative analysis of known variants and a novel 27 bp deletion in the promoter region

BACKGROUND

The human dopamine D4 receptor (DRD4) is a candidate gene of great interest in molecular studies of human personality and psychiatric disorders. This gene is unique in having an exceptionally high amount of polymorphic sites both in the coding and in the promoter region.

RESULTS

We report the identification of a new 27 bp deletion starting 524 bp upstream of the initiation codon (27 bp del) of the dopamine D4 receptor (DRD4) gene, in the close vicinity of the -521C>T SNP. The presence of the 27 bp deletion leads to the misgenotyping of the -616C>G SNP by the Sau96 I RFLP method, thus the genotype determination of the mutation is of additional importance. The frequency of this novel sequence variation is considerably low (allele frequency is = 0.16%), as no homozygotes, and only 3 heterozygote carriers were found in a healthy, unrelated Caucasian sample (N = 955).

CONCLUSION

Remarkably, the deleted region contains consensus sequences of binding sites for several known transcription factors, suggesting that the different alleles may affect the transcriptional regulation of the gene. A comparison of methods and results for the allelic variations of the DRD4 gene in various ethnic groups is also discussed, which has a high impact in psychiatric genetic studies.

sgk1, a member of an RNA cluster associated with cell death in a model of Parkinson's disease

In an effort to gain deeper insight into the molecular processes underlying neurodegeneration in Parkinson's disease, we performed gene expression profiling at several early time points after MPTP-injection into old (1-year) mice. We used a PCR-based gene expression profiling method, digital expression pattern display (DEPD), a method of very high sensitivity and reproducibility, which displays almost all transcripts of a tissue. To identify cell death-associated genes, we defined clusters of differentially expressed transcripts with expression behaviour that correlated with the temporal profile of cell death progression and characterized one of these cell death clusters further. We selected one of the strongest regulated genes, the serum and glucocorticoid-regulated kinase 1 (sgk1), and validated its differential expression by Northern blot analysis, semiquantitative PCR and in situ hybridization. Up-regulation of sgk1 (i) coincides with the onset of dopaminergic cell death in both the 8-week acute and 1-year subacute MPTP models, (ii) spans the entire brain, (iii) is attenuated by the l-deprenyl-mediated inhibition of the MPTP conversion to its active metabolite MPP+ and (iv) is not induced by dehydration. This study demonstrated that the combination of the DEPD technology, clustering analysis and a detailed histopathology is a useful tool for elucidating molecular pathways in neurodegenerative diseases.

Transcriptional regulation of mouse mu opioid receptor gene: Sp3 isoforms (M1, M2) function as repressors in neuronal cells to regulate the mu opioid receptor gene

The 5'-flanking region of the mouse mu opioid receptor (MOR) gene has two promoters, referred to as distal and proximal. MOR mRNA is predominantly initiated by the proximal promoter. Previously, several important cis-elements and trans-factors have been shown to play a functional role in the proximal promoter of the MOR gene. In this study, we defined another functional, negative regulatory element located in the -219- to -189-base pair (translational start site designed as +1) region of the proximal promoter. It is designated as the Sp binding sequence for its sequence homology to the consensus Sp binding element. Mutation of the Sp binding element led to a 100% increase of MOR promoter activity in MOR-positive cells (NMB cells), confirming the negative role of the Sp binding sequence. Surprisingly, electrophoretic mobility shift analysis and chromatin immunoprecipitation assays revealed that Sp3 and its isoforms (M1 and M2) were specifically bound to the Sp binding sequence. In cotransfection assays of Drosophila melanogaster SL2 cells using cDNA encoding Sp1, Sp3, and the M1 and M2 isoforms of Sp3, the M1 and M2 isoforms trans-repressed the MOR promoter, whereas Sp1 and Sp3 trans-activated the MOR promoter. Significantly, ectopic expression of the M1 and M2 isoforms of Sp3 led to repression of the endogenous MOR gene transcripts in NMB cells. These results suggest that the binding of the M1 and M2 isoforms of the Sp3 transcription factor to the Sp binding sequence may play a role in mouse MOR gene expression.

Caffeine regulates neuronal expression of the dopamine 2 receptor gene

The psychoactive drug caffeine influences neuronal physiology; however, it is unknown whether it can dynamically alter the expression of genes that influence neurotransmission. Here, we report that caffeine stimulates transcription of the dopamine 2 receptor (D2R) gene in PC-12 cells and primary striatal cultures and increases D2R protein expression in the striatum. Physiological doses of caffeine and the specific adenosine 2A receptor antagonist 8-(3-chlorostyryl) caffeine both increased the activity of a D2R/luciferase reporter construct within 24 h, and simultaneous treatment with 2-[p-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680), a specific adenosine 2A receptor agonist, eliminated this effect. Tests of additional constructs revealed that specific regions of the D2R promoter (-117/-75) and 5'-untranslated region (+22/+317) were required for activation of D2R gene expression by caffeine. In primary striatal cultures, caffeine increased spontaneous firing of neurons between 12 and 80 min after treatment, whereas it increased D2R mRNA expression after only 4 h. These results indicate that regulation of D2R gene expression by caffeine occurs after the initial physiological response has subsided. In vivo, female mice treated with a dose of caffeine (50 mg/kg) showed 1.94- and 2.07-fold increases in D2R mRNA and protein expression, respectively. In contrast, male mice exhibited a 31% decrease in D2R mRNA expression and showed no changes in D2R protein expression. Collectively, these results demonstrate for the first time that caffeine alters D2R expression in neurons. They also suggest that caffeine consumption can lead to sexually dimorphic patterns of gene expression in the brain.

Mouse mu opioid receptor distal promoter transcriptional regulation by SOX proteins

We have identified transcription factors that bind to specific sequences in 5'-distal promoter regulatory sequences of the mouse mu opioid receptor (mor) promoter using the yeast one-hybrid system. The sequence between -746 and -707 in mor distal promoter was used as the bait because it acts as a functional promoter element and binds several DNA-binding proteins. From an adult mouse brain cDNA library, five cDNA clones encoding three Sox gene family (Sry like high mobility group (HMG) box gene) transcriptional factors, mSOX18, mSOX21, and mSOX6, were isolated. Electrophoretic mobility shift assays confirmed the presence of a binding site for SOX proteins in the -731/-725 region. Additionally, we have also established that the flanking regions outside the core Sox-binding site play an essential role in high affinity binding. DNase I footprint analysis indicates that proteins from mouse brain interact with the Sox-binding site within the mor distal promoter. Finally, we demonstrated that overexpression of mSOX18 and/or mSOX21 was able to up-regulate mouse mor distal promoter activity in mor-expressing neuronal cells (NMB). These data indicate that SOX proteins might contribute to the transcriptional activity of the mor gene and suggest that mu opioid receptor could mediate some of the developmental processes in which SOX proteins are included.

Activation of the rat dopamine D2 receptor promoter by mitogen-activated protein kinase and Ca2+/calmodulin-dependent protein kinase II pathways

To investigate regulation of D2 receptor (D2R) gene expression by protein kinases, we evaluated effects of constitutively active MAPK kinase kinase (MEKK), Ca2+/calmodulin-dependent protein kinase (CaMK) II, CaMKIV and cyclic AMP-dependent protein kinase (PKA) on D2R promoter activity using luciferase reporter gene assays. A 1.5-kbp fragment containing the rat D2R promoter was cloned upstream of the reporter and transfected into D2R-expressing NB2A cells or nonexpressing NG108-15 and C6 glioma cells. MEKK and CaMKII, but not CaMKIV and PKA, increased promoter activity 4.5- and 1.5-fold, respectively, in NB2A cells. Inhibitory effects of a MEK inhibitor and lack of effect by dominant negative (DN)-JNK1 or DN-p38MAPK revealed that ERK but not JNK and p38MAPK is involved in MEKK-induced promoter activation. Deletion and mutation of the promoter revealed that the MEKK-responsive region was Sp1 site B between nucleotides -56 and -47. Overexpression of Sp1 suppressed promoter activity without affecting MEKK-induced activation. Interestingly, overexpression of Zif268 increased promoter activity through the region between nucleotides -56 and -36. Increased activity by Zif268 was additive with CaMKII-induced activation but not with activation induced by MEKK. Co-transfection with CaMKII stimulated nuclear translocation of Zif268. These results suggest that ERK and CaMKII positively regulate the D2R promoter and that Zif268 is a potential transcription factor for the CaMKII-dependent pathway.

Functional analysis of basic transcription element (BTE)-binding protein (BTEB) 3 and BTEB4, a novel Sp1-like protein, reveals a subfamily of transcriptional repressors for the BTE site of the cytochrome P4501A1 gene promoter

The Sp1-like family of transcription factors is emerging as an integral part of the cellular machinery involved in the control of gene expression. Members of this family of proteins contain three highly homologous C-terminal zinc-finger motifs that bind GC-rich sequences found in the promoters of a diverse number of genes, such as the basic transcription element (BTE) in the promoter of the carcinogen-metabolizing cytochrome P4501A1 (CYP1A1) gene. In the present study, we report the molecular and functional characterization of BTE-binding protein (BTEB) 4, a novel ubiquitously expressed member of the Sp1-like proteins family. This protein represents a new homologue of BTEB1, originally described as a regulator of the BTE site in the CYP1A1 gene promoter. Similarly to the recently described BTEB3, we demonstrate that the N-terminal region of BTEB4 directly represses transcription and binds the co-repressor mSin3A. In addition, we show that the C-terminal zinc-finger domain of BTEB4 binds specifically the BTE site of the CYP1A1 promoter, similar to BTEB1 and BTEB3. Also, we show that both BTEB3 and BTEB4 repress the CYP1A1 gene promoter via the BTE site in HepG2 and BxPC3 cells. Thus the identification of this protein expands the repertoire of BTEB-like members of the Sp1-like protein family involved in transcriptional repression. Furthermore, our results demonstrate that the BTEB subfamily can repress the CYP1A1 gene promoter via the BTE site.

Functional domains and DNA-binding sequences of RFLAT-1/KLF13, a Krüppel-like transcription factor of activated T lymphocytes

RFLAT-1/KLF13, a member of the Krüppel-like family of transcription factors, was identified as a transcription factor expressed 3-5 days after T lymphocyte activation. It binds to the promoter of the chemokine gene RANTES (regulated on activation normal T cell expressed and secreted) and regulates its "late" expression in activated T-cells. In this study, a series of experiments to define the functional domains of RFLAT-1/KLF13 were undertaken to further advance the understanding of the molecular mechanisms underlying transcriptional regulation by this factor. Using the GAL4 fusion system, distinct transcriptional activation and repression domains were identified. The RFLAT-1 minimum activation domain is localized to amino acids 1-35, whereas the repression domain resides in amino acids 67-168. Deletion analysis on the RFLAT-1 protein further supports these domain functions. The RFLAT-1 activation domain is similar to that of its closest family member, basic transcription element-binding protein 1. This domain is highly hydrophobic, and site-directed mutagenesis demonstrated that both negatively charged and hydrophobic residues are important for transactivation. The nuclear localization signal of RFLAT-1 was also identified using the RFLAT-1/green fluorescence protein fusion approach. RFLAT-1 contains two potent, independent nuclear localization signals; one is immediately upstream of the zinc finger DNA-binding domain, and the other is within the zinc fingers. Using mutational analysis, we also determined that the critical binding sequence of RFLAT-1 is CTCCC. The intact CTCCC box on the RANTES promoter is necessary for RFLAT-1-mediated RANTES transcription and is also required for the synergy between RFLAT-1 and NF-kappaB proteins.

Multiplex three-dimensional brain gene expression mapping in a mouse model of Parkinson's disease

To facilitate high-throughput 3D imaging of brain gene expression, a new method called voxelation has been developed. Spatially registered voxels (cubes) are analyzed, resulting in multiple volumetric maps of gene expression analogous to the images reconstructed in biomedical imaging systems. Using microarrays, 40 voxel images for 9000 genes were acquired from brains of both normal mice and mice in which a pharmacological model of Parkinson's disease (PD) had been induced by methamphetamine. Quality-control analyses established the reproducibility of the voxelation procedure. The investigation revealed a common network of coregulated genes shared between the normal and PD brain, and allowed identification of putative control regions responsible for these networks. In addition, genes involved in cell/cell interactions were found to be prominently regulated in the PD brains. Finally, singular value decomposition (SVD), a mathematical method used to provide parsimonious explanations of complex data sets, identified gene vectors and their corresponding images that distinguished between normal and PD brain structures, most pertinently the striatum.

Developmental expression of the zinc finger transcription factor DRRF (dopamine receptor regulating factor)

Dopamine receptor regulating factor (DRRF) is a novel transcription factor with unique anatomical distribution and functional properties, suggesting its importance in regulating dopaminergic neurotransmission. To gain insight into the in vivo function of this factor during embryogenesis, we studied its distribution at embryonic days E8-E16 in the mouse using in situ hybridization. DRRF mRNA is expressed uniquely during development at all time points tested with high levels observed at E12, E14 and E16 in various tissues. DRRF expression is also found in particular brain regions, such as the neopallial cortex, olfactory lobe and corpus striatum. This pattern of DRRF distribution during embryogenesis overlaps with that found in the adult brain, and with the expression profile of dopamine receptors both in the adult and during development.

Role of dopamine receptors in the kidney in the regulation of blood pressure

Regulation by dopamine of cardiovascular function, renal function and systemic blood pressure regulation is multifaceted. Each of the five dopamine receptor subtypes participates in the regulation of blood pressure by mechanisms specific for the subtype. Some receptors regulate blood pressure by influencing the central or peripheral nervous system; others influence epithelial transport and regulate the secretion and receptors of several humoral agents. The D1, D3, and D4 receptors interact with the renin-angiotensin system, while the D2 and D5 receptors interact with the sympathetic nervous system to regulate blood pressure.