Dynamic regulation of mitochondrial function by glucocorticoids.

Glucocorticoids play an important biphasic role in modulating neural plasticity; low doses enhance neural plasticity and spatial memory behavior, whereas chronic, higher doses produce inhibition. We found that 3 independent measures of mitochondrial function-mitochondrial oxidation, membrane potential, and mitochondrial calcium holding capacity-were regulated by long-term corticosterone (CORT) treatment in an inverted "U"-shape. This regulation of mitochondrial function by CORT correlated with neuroprotection; that is, treatment with low doses of CORT had a neuroprotective effect, whereas treatment with high doses of CORT enhanced kainic acid (KA)-induced toxicity of cortical neurons. We then undertook experiments to elucidate the mechanisms underlying these biphasic effects and found that glucocorticoid receptors (GRs) formed a complex with the anti-apoptotic protein Bcl-2 in response to CORT treatment and translocated with Bcl-2 into mitochondria after acute treatment with low or high doses of CORT in primary cortical neurons. However, after 3 days of treatment, high, but not low, doses of CORT resulted in decreased GR and Bcl-2 levels in mitochondria. As with the in vitro studies, Bcl-2 levels in the mitochondria of the prefrontal cortex were significantly decreased, along with GR levels, after long-term treatment with high-dose CORT in vivo. These findings have the potential to contribute to a more complete understanding of the mechanisms by which glucocorticoids and chronic stress regulate cellular plasticity and resilience and to inform the future development of improved therapeutics.

BAG1 plays a critical role in regulating recovery from both manic-like and depression-like behavioral impairments.

Recent microarray studies with stringent validating criteria identified Bcl-2-associated athanogene (BAG1) as a target for the actions of medications that are mainstays in the treatment of bipolar disorder (BPD). BAG1 is a Hsp70/Hsc70-regulating cochaperone that also interacts with glucocorticoid receptors (GRs) and attenuates their nuclear trafficking and function. Notably, glucocorticoids are one of the few agents capable of triggering both depressive and manic episodes in patients with BPD. As a nexus for the actions of glucocorticoids and bipolar medications, we hypothesized that the level of BAG1 expression would play a pivotal role in regulating affective-like behaviors. This hypothesis was investigated in neuron-selective BAG1 transgenic (TG) mice and BAG1 heterozygous knockout (+/-) mice. On mania-related tests, BAG1 TG mice recovered much faster than wild-type (WT) mice in the amphetamine-induced hyperlocomotion test and displayed a clear resistance to cocaine-induced behavioral sensitization. In contrast, BAG1+/- mice displayed an enhanced response to cocaine-induced behavioral sensitization. The BAG1 TG mice showed less anxious-like behavior on the elevated plus maze test and had higher spontaneous recovery rates from helplessness behavior compared with WT mice. In contrast, fewer BAG1+/- mice recovered from helplessness behavior compared with their WT controls. BAG1 TG mice also exhibited specific alterations of hippocampal proteins known to regulate GR function, including Hsp70 and FKBP51. These data suggest that BAG1 plays a key role in affective resilience and in regulating recovery from both manic-like and depression-like behavioral impairments.

Genome-wide gene expression profiling in GluR1 knockout mice: key role of the calcium signaling pathway in glutamatergically mediated hippocampal transmission.

Alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors (AMPARs) convey fast synaptic transmission in the CNS and mediate various forms of hippocampal plasticity. Disruption of glutamate receptor type 1 (GluR1), a member of the AMPAR family, causes synaptic alterations and learning/memory deficits in mice. To gain mechanistic insight into the synaptic and behavioral changes associated with GluR1 deletion, hippocampal genome-wide expression profiling was conducted using groups of GluR1 knockout (KO) mice and their wild-type littermates. Regulation of 38 genes was found to be altered more than 30% (P < 0.01, n = 8), and seven of these genes were studied with additional quantitative experiments. A large portion of the altered genes encoded molecules involved in calcium signaling, including calcium channel components, calcium-binding proteins and calcium-calmodulin-dependent protein kinase II subunits. At the protein level, we further evaluated some genes in the calcium pathway that were altered in GluR1 KO mice. Protein levels of two key molecules in the calcium pathway - GluR, ionotropic, N-methyl-d-aspartate-1 and calcium/calmodulin-dependent protein kinase II alpha - showed similar changes to those observed in mRNA levels. These findings raise the possibility that calcium signaling and other plasticity molecules may contribute to the hippocampal plasticity and behavioral deficits observed in GluR1 KO mice.

Common effects of lithium and valproate on mitochondrial functions: protection against methamphetamine-induced mitochondrial damage.

Accumulating evidence suggests that mitochondrial dysfunction plays a critical role in the progression of a variety of neurodegenerative and psychiatric disorders. Thus, enhancing mitochondrial function could potentially help ameliorate the impairments of neural plasticity and cellular resilience associated with a variety of neuropsychiatric disorders. A series of studies was undertaken to investigate the effects of mood stabilizers on mitochondrial function, and against mitochondrially mediated neurotoxicity. We found that long-term treatment with lithium and valproate (VPA) enhanced cell respiration rate. Furthermore, chronic treatment with lithium or VPA enhanced mitochondrial function as determined by mitochondrial membrane potential, and mitochondrial oxidation in SH-SY5Y cells. In-vivo studies showed that long-term treatment with lithium or VPA protected against methamphetamine (Meth)-induced toxicity at the mitochondrial level. Furthermore, these agents prevented the Meth-induced reduction of mitochondrial cytochrome c, the mitochondrial anti-apoptotic Bcl-2/Bax ratio, and mitochondrial cytochrome oxidase (COX) activity. Oligoarray analysis demonstrated that the gene expression of several proteins related to the apoptotic pathway and mitochondrial functions were altered by Meth, and these changes were attenuated by treatment with lithium or VPA. One of the genes, Bcl-2, is a common target for lithium and VPA. Knock-down of Bcl-2 with specific Bcl-2 siRNA reduced the lithium- and VPA-induced increases in mitochondrial oxidation. These findings illustrate that lithium and VPA enhance mitochondrial function and protect against mitochondrially mediated toxicity. These agents may have potential clinical utility in the treatment of other diseases associated with impaired mitochondrial function, such as neurodegenerative diseases and schizophrenia.

The monoamine oxidase B gene exhibits significant association to ADHD.

Attention deficit hyperactivity disorder (ADHD) is a common neuropsychiatric condition with strong genetic basis. Recent work in China indicated that ADHD may be linked to Xp1-2 in the Han Chinese population. The gene encoding monoamine oxidase B (MAOB), the main enzyme degrading dopamine in the human brain, is located in this region. The current study sequenced the exons and the 5' and 3' flanking regions of the MAOB gene and found four common variants including 2276C>T and 2327C>T in exon 15, rs1799836 in intron 13 and rs1040399 in 3'-UTR. We assessed the association of these variants with ADHD in 548 trios collected from 468 males and 80 females probands. TDT analysis showed that alleles of each polymorphism were preferentially transmitted to probands (rs1799836, P = 3.28E-15; rs1040399, P = 1.87E-6; 2276T>C or 2327T>C, P = 2.20E-6) and haplotype-based TDT analyses also found distorted transmission. In conclusion, this study provides the strongest evidence for the involvement of MAOB gene in the etiology of ADHD to date, at least in Han Chinese population.

[Association between serotonin 4 gene polymorphisms and attention deficit hyperactivity disorder comorbid or not comorbid disruptive behavioral disorder].

OBJECTIVE: To investigate the relationship between three HTR4 gene polymorphisms, 83097 C>T, 83198 A>G as well as -36C>T polymorphisms, and attention deficit hyperactivity disorder (ADHD) comorbid or not comorbid disruptive behavioral disorder (DBD). METHODS: Blood samples were taken from 152 trios with probands of ADHD comorbid DBD and 173 trios with probands of ADHD not comorbid DBD. DNA was extracted. 83097 C>T, 83198 A>G and -36C>T were genotyped by restriction fragment length polymorphism analysis. Transmit/disequilibrium test and haplotype analysis were used to test the association of the three polymorphisms with ADHD comorbid or not comorbid DBD separately. RESULTS: Haplotype T/G/T showed tendency of over transmission (chi(2)=3.470,P=0.062) to probands of ADHD with DBD, while haplotype C/G/T (chi(2)=4.568,P=0.032) and C/G/C (chi(2)=5.333,P=0.021) were under transmitted to probands of ADHD without DBD, No biased transmissions of any allele were found in families with probands of ADHD with and without DBD. CONCLUSION: Whether ADHD comorbid DBD or not comorbid DBD makes difference at the level of HTR4 gene polymorphisms.

[Association between serotonin 1D gene polymorphisms and attention deficit hyperactivity disorder comorbid or not comorbid learning disorder].

OBJECTIVE: To investigate the relationship between two HTR1D gene polymorphisms, 1350T>C and 1236A>G polymorphisms, and attention deficit hyperactivity disorder (ADHD) comorbid or not comorbid learning disorder (LD). METHODS: Blood samples were taken from 91 trios with probands of ADHD comorbid LD and 181 trios with probands of ADHD not comorbid LD. DNA was extracted. 1350T>C and 1236A>G were genotyped by restriction fragment length polymorphism analysis. Transmit/disequilibrium test and haplotype analysis were used to test the association between the two polymorphisms of HTR1D gene and ADHD comorbid or not comorbid LD separately. RESULTS: 1236A allele (chi2=5.306, P=0.021) was over transmitted to probands of ADHD without LD. No biased transmissions of any allele and haplotype were found in families with probands of ADHD with LD. CONCLUSION: whether ADHD comorbid LD or not comorbid LD makes difference at the level of HTR1D gene polymorphism of 1236A>G.

The anti-apoptotic, glucocorticoid receptor cochaperone protein BAG-1 is a long-term target for the actions of mood stabilizers.

Increasing data suggest that impairments of cellular plasticity/resilience underlie the pathophysiology of bipolar disorder. A series of microarray studies with validating criteria have recently revealed a common, novel target for the long-term actions of the structurally highly dissimilar mood stabilizers lithium and valproate: BAG-1 [BCL-2 (B-cell CLL/lymphoma 2)-associated athanogene]. Because BAG-1 attenuates glucocorticoid receptor (GR) nuclear translocation, activates ERK (extracellular signal-regulated kinase) MAP (mitogen-activated protein) kinases, and potentiates anti-apoptotic functions of BCL-2, extensive additional studies were undertaken. Chronic administration of both agents at therapeutic doses increased the expression of BAG-1 in rat hippocampus. Furthermore, these findings were validated at the protein level, and the effects were seen in a time frame consistent with therapeutic effects and were specific for mood stabilizers. Functional studies showed that either lithium or valproate, at therapeutically relevant levels, inhibited dexamethasone-induced GR nuclear translocation and inhibited GR transcriptional activity. Furthermore, small interfering RNA studies showed that these inhibitory effects on GR activity were mediated, at least in part, through BAG-1. The observation that BAG-1 inhibits glucocorticoid activation suggests that mood stabilizers may counteract the deleterious effects of hypercortisolemia seen in bipolar disorder by upregulating BAG-1. Additionally, these studies suggest that regulation of GR-mediated plasticity may play a role in the treatment of bipolar disorder and raise the possibility that agents affecting BAG-1 more directly may represent novel therapies for this devastating illness.

Association of attention-deficit/hyperactivity disorder with serotonin 4 receptor gene polymorphisms in Han Chinese subjects.

Attention-deficit/hyperactivity disorder (ADHD) is an important public health problem. Although serotonin is believed to be an important neurotransmitter in the etiology of this disorder, it remains unclear which specific 5-HT receptors are involved in regulating the symptoms of ADHD. Previous studies have provided favorable evidence for the association of ADHD with both the serotonin transporter gene and serotonin 1B receptor gene. To further investigate the role of other genes of the serotonergic pathway in ADHD, the current study examined variants of the serotonin 4 receptor gene in a relatively large sample of ADHD nuclear families. The T allele of the 83097 C>T polymorphism of HTR4 showed a tendency of preferential transmission to probands with ADHD (chi(2)=2.699, P=0.100). When haplotype TDT analysis of HTR4 was performed, we further found that the C/G haplotype of the 83097 C>T and 83198 A>G polymorphisms (chi(2)=8.783, P=0.003) and the C/G/C haplotype of these and the -36 C>T polymorphism (chi(2)=5.762, P=0.016) were under-transmitted to probands with ADHD. These results suggest that the HTR4 gene may play a role in the genetic predisposition to ADHD.

No association of attention-deficit/hyperactivity disorder with genes of the serotonergic pathway in Han Chinese subjects.

Attention-deficit/hyperactivity disorder (ADHD) is a complex psychiatric syndrome with cardinal symptoms of inattention, hyperactivity and impulsivity, and is a significant risk factor for poor health outcomes in both adolescence and adulthood. Etiology is clearly multifactoral, with probable contributions from both genetic and environmental factors. The genetic contribution is prominent, with estimated heritability at about 0.80. Although effects in dopamine metabolism have long been implicated in the etiology of ADHD, the role for serotonin has gained more attention in recent years. The current study examined five variants in three serotonin genes [those that code for serotonin receptors 2A (HTR2A), 5A (HTR5A) and 6 (HTR6)] in a relatively large sample of ADHD nuclear families. The transmission disequilibrium test (TDT) and the extended transmission disequilibrium test (ETDT) were performed to test for evidence of distorted transmission of alleles or haplotypes. No significant biased transmission was observed. These results do not support a substantial role of these serotonin gene in ADHD, however, additional work may be warranted before this association is definitively discounted.

Association between polymorphisms in serotonin 2C receptor gene and attention-deficit/hyperactivity disorder in Han Chinese subjects.

Attention deficit hyperactivity disorder (ADHD) is much more frequent in males than females, so several genes on the X chromosome (e.g., MAOA and MAOB) have been pursued as candidates for influencing risk for the disorder. HTR2C is also located on the X chromosome. In the current study, we examined the relationship between the C-759T and G-697C polymorphisms of HTR2C and ADHD in 488 Han Chinese families. Transmission Disequilibrium Test (TDT) analysis showed that the -759C allele, the -697G allele, and haplotype -759C/-697G were significantly over-transmitted to affected probands, while haplotypes -759C/-697C and -759T/-697C were under-transmitted. When families were divided into three subtypes according to the diagnosis of probands, the -697G allele and haplotype -759C/-697G were significantly over transmitted to ADHD-C probands, while haplotype -759T/-697C was under-transmitted to these individuals; however, no biased transmission of any allele or haplotype was observed for probands with ADHD-I, suggesting that different subtypes of ADHD have different genetic influences. Our findings highlight the need to explore the role of 5-HT2C receptor dysfunction in the pathogenesis of ADHD.

Possible role of potassium channel, big K in etiology of schizophrenia.

Schizophrenia (SZ), a common severe mental disorder, affecting about 1% of the world population. However, the etiology of SZ is still largely unknown. It is believed that molecules that are in an association with the etiology and pathology of SZ are neurotransmitters including dopamine, 5-HT and gamma-aminobutyric acid (GABA). But several lines of evidences indicate that potassium large conductance calcium-activated channel, known as BK channel, is likely to be included. BK channel belongs to a group of ion channels that plays an important role in regulating neuronal excitability and transmitter releasing. Its involvement in SZ emerges as a great interest. For example, commonly used neuroleptics, in clinical therapeutic concentrations, alter calcium-activated potassium conductance in central neurons. Diazoxide, a potassium channel opener/activator, showed a significant superiority over haloperidol alone in the treatment of positive and general psychopathology symptoms in SZ. Additionally, estrogen, which regulates the activity of BK channel, modulates dopaminergic D2 receptor and has an antipsychotic-like effect. Therefore, we hypothesize that BK channel may play a role in SZ and those agents, which can target either BK channel functions or its expression may contribute to the therapeutic actions of SZ treatment.

Stress-induced change of mitochondria membrane potential regulated by genomic and non-genomic GR signaling: a possible mechanism for hippocampus atrophy in PTSD.

Posttraumatic stress disorder (PTSD) is a common psychiatric disorder often accompanied by morphologic changes in the hippocampus. Brain imaging studies have demonstrated a strong relationship between PTSD and a reduction in the volume of the hippocampus; however, the mechanisms that cause such atrophy are not well understood. In an attempt to expand our knowledge of these mechanisms, our theory has focused on the role of mitochondria in cell death, which may be associated with atrophy of the hippocampus. In addition to their function in respiration, mitochondria play an important role in the regulation of cytochrome c, an apoptotic signaling element. Normally, cytochrome c resides in the intermembrane space of mitochondria, where membrane potential exists-negative inside of about 180-200mV. In response to a variety of apoptotic stimuli, mitochondria membrane potential can be changed by genomic and non-genomic cortisol action. For the non-genomic action, stress increases cortisol levels, which activates the glucocorticoid receptor (GR). Stress-activated GR directly binds to mitochondrial membranes to regulate membrane potential. The GR will also produce a genomic action, in which GR, in interacting with several other molecules (such as heat shock proteins 90/70/40, etc.), translocates into the nucleus of the cell, where it binds to DNA and exerts transcriptional action. As one of the downstream modulaters of GR activation, Bax can be up regulated and translocated to the mitochondria, where it binds to modulator of apoptosis-1 (MAP-1), a mitochondrial effector of BAX to cause change Deltapsi. These non-genomic and genomic cortisol-induced changes of the mitochondrial membrane potential can result in the release of cytochrome c from the mitochondria to the cytoplasm where the cytochrome c promotes of the action of caspases which leads to apoptosis. Therefore, we hypothesis that stress-induced changes of mitochondrial membrane potential are regulated by non-genomic and genomic actions of cortisol in hippocampal neurons. Understanding the molecular mechanism for stress-induced cell death in the hippocampus may shed a new light on developing a mitochondrial membrane potential related therapeutic drug and/or diagnostic tool for PTSD.

Identification of gene markers based on well validated and subcategorized stressed animals for potential clinical applications in PTSD.

Post-traumatic stress disorder (PTSD) is a complex mental disorder that can develop in response to traumatic experiences. The molecular mechanisms underlying the pathology of PTSD are poorly understood, and this lack of knowledge hampers our ability to find superior therapeutic approaches to the treatment of this disorder. There are two main reasons for our lack of study in this area: here is no sufficiently validated animal model and lack of large-scale studies for the search of underlying molecular mechanisms. Thus, to promote research on PTSD (especially its molecular mechanisms) and to set molecular basis for searching novel medications of this disorder, large-scale, genome-wide interrogation of a significant amount of genes based upon a well validated animal model is demanded. We hypothesize that a significant number of genes are involved in PTSD. It is only with a large number of these genes identified in specific samples of PTSD-related population, and then it is possible for a sufficient understanding of the pathology at the molecular level of a PTSD, as well as for enhancing the PTSD's therapeutic and preventative strategies. Two prerequisites are needed for testing this hypothesis: (1) relative pure samples from a well validated animal model; and (2) genome-wide screening of PTSD molecular targets. For the animal model, we suggest to use the predator-exposure paradigm, in which rats are exposed to a predator, this model has previously been evaluated behaviorally well emulated the clinical symptoms of PTSD. For a better stringency, three criteria can be used to further validate this animal model: analogous (similarity of behavior), predictive (predictability of drug response) and biological mechanism (e.g., electrophysiological and pathological change in amygdala). For large-scale molecular target screening, the new microarray technology, which can profile expression of tens of thousands genes simultaneously, is the method of choice. The validity and practicability of this hypothesis and the strategy for its testing have been supported by our preliminary laboratory data.

[Association between serotonin 1D gene polymorphisms and attention deficit hyperactivity disorder comorbid or not comorbid disruptive behavior disorder].

OBJECTIVE: To investigate the relationship between two HTR1D gene polymorphisms, that is 1350T > C and 1236A > G polymorphisms, and attention deficit hyperactivity disorder (ADHD) comorbid or not comorbid disruptive behavior disorder (DBD). METHODS: Blood samples were taken from 90 trios with probands of ADHD comrbid DBD and 182 trios with probands of ADHD not comorbid DBD. DNA was extracted. 1350T > C and 1236A > G were genotyped by restriction fragment length polymorphism analysis. Transmit/disequilibrium test and haplotype analysis were used to test the association of the two polymorphisms of HTR1D gene and ADHD comorbid or not comorbid disruptive behavior disorder (DBD) separately. RESULTS: 1350T allele(chi2 = 3.67, P = 0.055)and G/T haplotype(chi2 = 3.84, P = 0.050)were overtransmitted, while 1350C allele(chi2 = 3.67, P = 0.055) and G/C haplotype(chi2 = 5.22, P = 0.022)were undertransmitted to probands of ADHD with DBD. No biased transmission of any allele and haplotype was found in families with probands of ADHD without DBD. CONCLUSION: ADHD comorbid or not comorbid DBD are different at the level of HTR1D gene polymrohisms of 1350T > C and 1236A > G. The current results indicate that ADHD with DBD has more heritable backgrounds when compared with ADHD without DBD.

Stepholidine protects against H2O2 neurotoxicity in rat cortical neurons by activation of Akt.

The fundamental pathological process(es) associated with schizophrenia (SZ) remain(s) uncertain, but multiple lines of evidence suggest that this condition is associated with excessive stimulation of striatal dopamine (DA) D2 receptors, deficient stimulation of medial prefrontal cortex (mPFC) D1 receptors as well as neuronal apoptosis. Unlike typical antipsychotics, stepholidine (SPD), which is isolated from the Chinese herb stephania, has D1 and D2 dual properties and regulates neuronal cell differentiation and proliferation. It is unknown, however, whether it possesses a neuroprotective property. Here, we report that SPD prevented neuronal cell death from H2O2 exposure and increased the levels of phosphorylated Akt (pAkt), a serine/threonine protein kinase. The SPD-induced neuroprotection and activation of Akt were blocked by LY294002, a PI3-K inhibitor, suggesting that the anti-apoptotic action of SPD is mediated via the PI3-K/Akt signaling pathway. Thus, as a survival or anti-apoptotic factor for neuronal cells, SPD may contribute to the therapeutic action of SPD in SZ treatment.

The use of mood stabilizers as plasticity enhancers in the treatment of neuropsychiatric disorders.

Mood disorders have traditionally been conceptualized as neurochemical disorders, but there is now evidence from a variety of sources demonstrating regional reductions in central nervous system (CNS) volume, as well as reductions in the numbers and/or sizes of glia and neurons in discrete brain areas. Although the precise cellular mechanisms underlying these morphometric changes remain to be fully elucidated, the data suggest that severe mood disorders are associated with impairments of structural plasticity and cellular resilience. It is thus noteworthy that lithium and valproate have recently been demonstrated to robustly increase the expression of the cytoprotective protein bcl-2 (an abbreviation for the B-cell lymphoma/leukemia-2 gene) in the CNS in vivo and in cells of human neuronal origin. Lithium and valproate also robustly activate a signaling cascade utilized by endogenous growth factors-the extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase pathway. Complementary human studies have shown that chronic lithium administration significantly increases gray matter content in a regionally selective manner, suggesting a reversal of illness-related atrophy and an increase in the volume of the neuropil. These unique and unexpected properties of lithium and valproate suggest that they may have broader utility as adjunctive agents in the treatment of a variety of neuropsychiatric disorders associated with cell atrophy or loss. The adjunctive use of these agents-at low doses-may provide the trophic support necessary to restore, enhance, and maintain normal synaptic connectivity, thereby allowing the chemical signal to reinstate the optimal functioning of critical circuits necessary for normal functioning.

[Association studies of dopamine D4 receptor gene and dopamine transporter gene polymorphisms in Han Chinese patients with attention deficit hyperactivity disorder].

OBJECTIVE: To investigate association of the 48 bp variable number of tandem repeat (VNTR) polymorphism in the D4 receptor gene (DRD4) exon 3 and 40 bp VNTR polymorphism in the dopamine transporter gene (DAT1) 3' untranslated region with attention deficit hyperactivity disorder (ADHD) in Han Chinese children. METHODS: The study samples were comprised of 340 ADHD children, 226 unrelated controls and 202 integrated ADHD trios (included proband and biological parents). The polymorphisms consisted of 48 bp VNTR in exon 3 of DRD4, and 40 bp VNTR in the 3' untranslated region of DAT1. Associations of polymorphisms with ADHD and its subtypes were examined by: (i) comparing cases and controls; and (ii) using family-based association study in an extension of exact transmission-disequilibrium test (ETDT) and haplotype-based haplotype relative risk (HHRR). RESULTS: The repeat numbers at the DRD4 48 bp locus ranged from 2-6 repeats in the Han Chinese controls, with the most common being the 4-repeat (77%) and 2-repeat (19.4%) alleles. Neither the 7-repeat allele nor longer repeats were found. For the DAT1, the repeat numbers at the 40 bp locus ranged from 6-7 repeats and 9-11 repeats. The 10-repeat allele was the most frequent (90.7%). The long-repeat alleles of DRD4 (ranging from 4-6 repeats) and DAT1 (ranging from 11-12 repeats), were present more frequently in ADHD probands than in controls. Our primary analyses failed to replicate the associations between ADHD and 7-repeat allele of DRD4 and the 10-repeat allele of DAT1. CONCLUSION: The long-repeat alleles of DRD4 (after a stratification by gender) and DAT1 may increase the risk for ADHD in Han Chinese children.

[Association studies of G352A polymorphism of dopamine transporter gene in Han Chinese attention deficit hyperactivity disorder patients].

OBJECTIVE: To investigate association of the new polymorphism G352A in the dopamine transporter gene (DAT1) exon 15 with attention deficit hyperactivity disorder (ADHD) in Han Chinese children. METHODS: The new mutant polymorphism G352A in the dopamine transporter gene (DAT1) exon 15 was found by the fluorescently-labeled dye-terminators assay. The study samples were comprised of 337 ADHD children, 207 unrelated controls and 201 integrated ADHD trios (included proband and biological parents). Associations of polymorphisms with ADHD and its subtypes were examined by: (i) comparing cases and controls; and (ii) using family-based association study in transmission-disequilibrium test (TDT). RESULTS: The allele frequencies at the DAT1 G352A locus in the control samples were 79.5% for 352G and 20.5% for 352A respectively. Association studies revealed no association between G352A in exon 15 of DAT1 and ADHD. But after a stratification by gender, there was possible association between G352A and ADHD girls: the 352G allele had a tendency to be preferentially transmitted to ADHD girls. CONCLUSION: There is no association between G352A, the new polymorphism, in exon 15 of DAT1 and ADHD. The 352G allele has a tendency to be preferentially transmitted to ADHD girls, but the findings require replication before drawing a definitive conclusion.

[Association between serotonin 2C gene polymorphisms and attention deficit hyperactivity disorder comorbid or not comorbid with learning disorder].

OBJECTIVE: To investigate the relationship between two HTR2C gene polymorphisms, that is C-759T and G-697C polymorphisms, and attention deficit hyperactivity disorder (ADHD) comorbid or not comorbid learning disorder (LD). METHODS: Blood samples were taken from 189 trios with probands of ADHD comorbid LD (ADHD+LD) and 299 trios with probands of ADHD not comorbid LD (ADHD-LD). DNA was extracted and PCR was performed to amplify the fragments containing both C-759T and G-697C polymorphisms. Aci I was used to detect different alleles of the two polymorphisms. Allele- based and haplotype- based TDT analysis were used to test the association of the two polymorphisms of HTR2C gene and ADHD-LD and ADHD+LD. RESULTS: -759C(chi(2)=6.961, P=0.008), -697G(chi(2)=8.346, P=0.004), as well as -759C/-697G haplotype were over- transmitted(chi(2)=9.000, P=0.002 7), while haplotype -759T/-697C was under- transmitted(chi(2)=7.784, P=0.005 3) to probands with ADHD-LD. No biased transmission of any allele and haplotype were found in families with probands of ADHD+LD. CONCLUSION: ADHD-LD and ADHD+LD are different at the level of HTR2C gene polymrohisms of C-759T and G-697C. HTR2C is related to ADHD-LD, while not related to ADHD+LD.