Adaptive behaviour deficits in individuals with 3q29 deletion syndrome.

BACKGROUND: 3q29 deletion syndrome (3q29del) is associated with a significantly increased risk for neurodevelopmental and neuropsychiatric phenotypes. Mild to moderate intellectual disability (ID) is common in this population, and previous work by our team identified substantial deficits in adaptive behaviour. However, the full profile of adaptive function in 3q29del has not been described nor has it been compared with other genomic syndromes associated with elevated risk for neurodevelopmental and neuropsychiatric phenotypes. METHODS: Individuals with 3q29del (n = 32, 62.5% male) were evaluated using the Vineland Adaptive Behaviour Scales, Third Edition, Comprehensive Parent/Caregiver Form (Vineland-3). We explored the relationship between adaptive behaviour and cognitive function, executive function, and neurodevelopmental and neuropsychiatric comorbidities in our 3q29del study sample, and we compared subjects with 3q29del with published data on fragile X syndrome, 22q11.2 deletion syndrome and 16p11.2 deletion and duplication syndromes. RESULTS: Individuals with 3q29del had global deficits in adaptive behaviour that were not driven by specific weaknesses in any given domain. Individual neurodevelopmental and neuropsychiatric diagnoses had a small effect on adaptive behaviour, and the cumulative number of comorbid diagnoses was significantly negatively associated with Vineland-3 performance. Both cognitive ability and executive function were significantly associated with adaptive behaviour, and executive function was a better predictor of Vineland-3 performance than cognitive ability. Finally, the severity of adaptive behaviour deficits in 3q29del was distinct from previously published data on comparable genomic disorders. CONCLUSIONS: Individuals with 3q29del have significant deficits in adaptive behaviour, affecting all domains assessed by the Vineland-3. Executive function is a better predictor of adaptive behaviour than cognitive ability in this population and suggests that interventions targeting executive function may be an effective therapeutic strategy.

Axis I psychiatric diagnoses in adolescents and young adults with 22q11 deletion syndrome.

BACKGROUND: 22q11.2 deletion syndrome (22q11DS) associates with schizophrenia spectrum disorders (SSDs), autism spectrum disorders (ASDs), and other psychiatric disorders, but co-occurrence of diagnoses are not well described. METHODS: We evaluated the co-occurrence of SSDs, ASDs and other axis I psychiatric diagnoses in 31 adolescents and adults with 22q11DS, assessing ASDs using either stringent Collaborative Program for Excellence in Autism (ASD-CPEA) criteria, or less stringent DSM-IV criteria alone (ASD-DSM-IV). RESULTS: Ten (32%) individuals met criteria for an SSD, five (16%) for ASD-CPEA, and five others (16%) for ASD-DSM-IV. Of those with ASD-CPEA, one (20%) met SSD criteria. Of those with ASD-DSM-IV, four (80%) met SSD criteria. Depressive disorders (8 individuals; 26%) and anxiety disorders (7; 23%) sometimes co-occurred with SSDs and ASDs. SSDs, ASDs, and anxiety occurred predominantly among males and depression predominantly among females. CONCLUSIONS: Individuals with 22q11DS can manifest SSDs in the presence or absence of ASDs and other axis I diagnoses. The results suggest that standard clinical care should include childhood screening for ASDs, and later periodic screening for all axis I diagnoses.

Regulation of mRNA expression encoding chaperone and co-chaperone proteins of the glucocorticoid receptor in peripheral blood: association with depressive symptoms during pregnancy.

BACKGROUND: Major depressive disorder during pregnancy associates with potentially detrimental consequences for mother and child. The current study examined peripheral blood gene expression as a potential biomarker for prenatal depressive symptoms. METHOD: Maternal RNA from whole blood, plasma and the Beck Depression Inventory were collected longitudinally from preconception through the third trimester of pregnancy in 106 women with a lifetime history of mood or anxiety disorders. The expression of 16 genes in whole blood involved in glucorticoid receptor (GR) signaling was assessed using real-time polymerase chain reaction. In parallel, plasma concentrations of progesterone, estradiol and cortisol were measured. Finally, we assessed ex vivo GR sensitivity in peripheral blood cells from a subset of 29 women. RESULTS: mRNA expression of a number of GR-complex regulating genes was up-regulated over pregnancy. Women with depressive symptoms showed significantly smaller increases in mRNA expression of four of these genes - FKBP5, BAG1, NCOA1 and PPID. Ex vivo stimulation assays showed that GR sensitivity diminished with progression of pregnancy and increasing maternal depressive symptoms. Plasma concentrations of gonadal steroids and cortisol did not differ over pregnancy between women with and without clinically relevant depressive symptoms. CONCLUSIONS: The presence of prenatal depressive symptoms appears to be associated with altered regulation of GR sensitivity. Peripheral expression of GR co-chaperone genes may serve as a biomarker for risk of developing depressive symptoms during pregnancy. The presence of such biomarkers, if confirmed, could be utilized in treatment planning for women with a psychiatric history.

Association of a polymorphism in the indoleamine- 2,3-dioxygenase gene and interferon-α-induced depression in patients with chronic hepatitis C.

Interferon (IFN)-α treatment for infectious diseases and cancer is associated with significant depressive symptoms that can limit therapeutic efficacy. Multiple mechanisms have been implicated in IFN-α-induced depression including immune, neuroendocrine and neurotransmitter pathways. To further explore mechanisms of IFN-α-induced depression and establish associated genetic risk factors, single nucleotide polymorphisms in genes encoding proteins previously implicated in IFN-α-induced depression were explored in two self-reported ethnic groups, Caucasians (n=800) and African Americans (n=232), participating in a clinical trial on the impact of three pegylated IFN-α treatment regimens on sustained viral response in patients with chronic hepatitis C. Before treatment, all subjects were free of psychotropic medications and had a score ≤20 on the Center for Epidemiologic Studies Depression Scale (CES-D), which was used to assess depressive symptom severity throughout the study. In Caucasians, a polymorphism (rs9657182) in the promoter region of the gene encoding indoleamine-2,3-dioxygenase (IDO1) was found to be associated with moderate or severe IFN-α-induced depressive symptoms (CES-D>20) at 12 weeks of IFN-α treatment (P=0.0012, P<0.05 corrected). Similar results were obtained for treatment weeks 24, 36 and 48. In subjects homozygous for the risk allele (CC, n=150), the odds ratio for developing moderate or severe depressive symptoms at treatment week 12 was 2.91 (confidence interval: 1.48-5.73) compared with TT homozygotes (n=270). rs9657182 did not predict depression in African Americans, who exhibited a markedly lower frequency of the risk allele at this locus. The findings in Caucasians further support the notion that IDO has an important role in cytokine-induced behavioral changes.

Prodromal symptoms in adolescents with 22q11.2 deletion syndrome and schizotypal personality disorder.

Adolescents with 22q11.2 Deletion Syndrome (22q11.2DS) and Schizotypal Personality Disorder (SPD) are at increased risk for the development of psychosis based, respectively, on genetic or behavioral factors. Thus both groups would be expected to manifest heightened rates of the prodromal signs that typically precede psychosis. Although there are now standardized procedures for assessing prodromal symptoms, there has been little research on the manifestation of these symptoms in 22q11.2DS patients, and no studies of differences in prodromal symptom patterns between genetically and behaviorally defined at-risk groups. In this study, demographically matched groups of 23 SPD, 23 22q11.2DS, and 23 control participants were administered the Structured Interview for Prodromal Syndromes (SIPS). Both risk groups showed elevated positive, negative, disorganized, and general prodromal symptoms, as well as elevations on 10 of the same individual symptom items, relative to the control group. Approximately 60% of individuals in the 22q11.2DS group and 70% of individuals in the SPD group met symptom criteria for a prodromal psychosis syndrome. The 22q11.2DS group scored significantly higher than the SPD group on the "decreased ideational richness" item and showed a trend toward greater motor abnormalities. The results suggest that these two high-risk groups are similar in prodromal symptom presentation, possibly as a result of overlapping causal mechanisms, and that standardized measures of prodromal syndromes like the SIPS can be used to identify 22q11.2DS patients at greatest risk for conversion to psychosis.

Performance on the Modified Card Sorting Test and its relation to psychopathology in adolescents and young adults with 22q11.2 deletion syndrome.

BACKGROUND: Approximately one-third of individuals with 22q11.2 deletion syndrome (22q11DS), a common genetic disorder highly associated with intellectual disabilities, may develop schizophrenia, likely preceded by a mild to moderate cognitive decline. METHODS: We examined adolescents and young adults with 22q11DS for the presence of executive function deficits using a modified version of the Wisconsin Card Sorting Test (MCST) and assessed whether specific performances were associated with concurrent schizophrenia-prodrome symptoms. We also examined possible relationships between MCST performance and broader indices of psychopathology, including self-reported internalising and externalising behavioural symptoms. RESULTS: Participants with 22q11DS scored significantly below age-matched controls on seven out of nine MCST measures, and poorer MCST performance was associated with increased positive prodromal and internalising behavioural symptoms. CONCLUSIONS: The schizophrenia-prodrome in 22q11DS involves executive dysfunction, and longitudinal investigation is necessary to examine if specific executive function impairments precedes or co-occurs with the emergence of behavioural psychopathology.

Functional polymorphisms in the interleukin-6 and serotonin transporter genes, and depression and fatigue induced by interferon-alpha and ribavirin treatment.

Depression and fatigue are frequent side effects of interferon-alpha (IFN-alpha) treatment, and there is compelling evidence that the inflammatory response system (including interleukin-6, IL-6) and the serotonergic system is important in the pathophysiology of such symptoms. Functional polymorphisms in the promoter region of the IL-6 gene (rs1800795) and serotonin transporter gene (5-HTTLPR) have been identified as regulating these systems. The present study aimed to determine if these polymorphisms were associated with the development of depression and fatigue during IFN-alpha and ribavirin treatment. Ninety-eight Caucasian patients receiving pegylated IFN-alpha and ribavirin treatment for chronic hepatitis C virus at King's College Hospital, London, and Emory University Hospital, Atlanta, participated in this prospective cohort study. Symptoms of depression and fatigue were measured before treatment and at weeks 4, 8, 12 and 24 during treatment. The 'low IL-6' synthesizing genotype (CC) was associated with significantly fewer symptoms of depression (effect size = 0.7 at week 24; F = 9.4, d.f. = 436, P = 0.002). The 'high transcription' serotonin transporter (5-HTT) genotype (LL) was also associated with significantly fewer symptoms of depression, but with a much smaller effect (effect size = 0.2 at week 24; F = 4.5, d.f. = 436, P = 0.03). Neither polymorphisms were associated with symptoms of fatigue (IL-6: F = 1.2, d.f. = 430, P = 0.2; 5-HTT: F = 0.5, d.f. = 430, P = 0.5). The smaller effects of the 5-HTT polymorphism on depression may be explained by an interaction between the genes (F = 5.0, d.f. = 434, P = 0.02): the 'protective' effect of the 5-HTTLPR polymorphism was evident only in the presence of the 'low IL-6' genotype (F = 5.4, d.f. = 64, P = 0.02), not in the presence of the 'high IL-6' genotype (F = 2.2, d.f. = 369, P = 0.1). The association between the IL-6 polymorphism and reduced risk of depressive symptoms confirms the role of the inflammatory response system in the pathophysiology of IFN-alpha-induced depression; in contrast, the effect of the 5-HTT gene was small and perhaps dependent on the status of the inflammatory response.

Human genetics of plasma dopamine beta-hydroxylase activity: applications to research in psychiatry and neurology.

RATIONALE: Norepinephrine (NE) is a key neurotransmitter in the central and peripheral nervous systems. Dopamine beta-hydroxylase (DbetaH) catalyzes the synthesis of NE from dopamine (DA) and occurs in the plasma as a stable heritable trait. Studies of this trait have been useful in psychiatric and neurological research. OBJECTIVE: To selectively and critically review the literature on plasma DbetaH, and on recent progress understanding the molecular genetic basis for its inheritance. Based on this review, directions for future research in psychiatry and neurology will be suggested. METHODS: We selectively review the literature on the biochemical and molecular genetics of plasma DbetaH activity, as well as research on plasma and cerebrospinal fluid (CSF) DbetaH in psychiatric and neurological disorders. RESULTS: Strong evidence implicates DBH, the structural locus encoding DbetaH enzyme, as the major quantitative trait locus influencing plasma DbetaH activity, with one single nucleotide polymorphism (SNP) accounting for up to 50% of the variance. Mutations at DBH appear to be responsible for the rare syndrome of DbetaH deficiency. Some biochemical and genetic studies suggest associations between low plasma or CSF DbetaH and psychotic symptoms in several psychiatric disorders. Studies combining genotyping at DBH with biochemical measurement of plasma DbetaH have proven useful in studies of schizophrenia, cocaine-induced paranoia (CIP), depression, attention deficit hyperactivity disorder, and alcoholism. Such studies may also elucidate the contribution of noradrenergic dysfunction to a variety of symptoms in Parkinson's disease and other degenerative neurological disorders. CONCLUSIONS: A model is proposed, in which lower levels of DbetaH protein may lead to elevated ratios of DA to NE. This model may explain associations between lower plasma DbetaH activity and vulnerability to psychotic symptoms. Genotype-controlled analysis of plasma DbetaH holds promise for promoting further progress in research on psychiatric and neurological disorders.

A quantitative-trait analysis of human plasma-dopamine beta-hydroxylase activity: evidence for a major functional polymorphism at the DBH locus.

Dopamine-beta-hydroxylase (D beta H) catalyzes the conversion of dopamine to norepinephrine and is released from sympathetic neurons into the circulation. Plasma-D beta H activity varies widely between individuals, and a subgroup of the population has very low activity levels. Mounting evidence suggests that the DBH structural gene is itself the major quantitative-trait locus (QTL) for plasma-D beta H activity, and a single unidentified polymorphism may account for a majority of the variation in activity levels. Through use of both sequencing-based mutational analysis of extreme phenotypes and genotype/phenotype correlations in samples from African American, European American (EA), and Japanese populations, we have identified a novel polymorphism (--1021C-->T), in the 5' flanking region of the DBH gene, that accounts for 35%--52% of the variation in plasma-D beta H activity in these populations. In EAs, homozygosity at the T allele predicted the very low D beta H-activity trait, and activity values in heterozygotes formed an intermediate distribution, indicating codominant inheritance. Our findings demonstrate that --1021C-->T is a major genetic marker for plasma-D beta H activity and provide new tools for investigation of the role of both D beta H and the DBH gene in human disease.

Functional variants at CYP2A6: new genotyping methods, population genetics, and relevance to studies of tobacco dependence.

Cytochrome P450CYP2A6 (CYP2A6) is the predominant enzyme responsible for the metabolism of nicotine to cotinine. Two variants have been identified that encode products presumed to have little or no activity. A previous study suggested that carriers of at least one copy of either null variant may be protected against tobacco dependence, while tobacco-dependent carriers smoke fewer cigarettes. However, different laboratories have reported widely disparate CYP2A6 allele frequencies across European populations. These differences prompted us to reexamine the genotyping methods for CYP2A6. We developed an improved genotyping strategy using CYP2A6-specific nested PCR, and differential restriction enzyme digestion to identify variant nucleotides in exon 3. We used sequencing to verify genotype results and to assess the sequence of exon 4, which previous work predicted should correspond to "wild-type" CYP2A6 sequence. In addition, we developed a new nomenclature in which CYP2A6*1 is designated CYP2A6*A1-*B1, CYP2A6*2 is CYP2A6*A2, and CYP2A6*3 is CYP2A6*B2. The frequencies of CYP2A6*A2 and CYP2A6*B2 were then estimated in samples from six populations. Sequencing confirmed CYP2A6*A2 genotypes in all cases. Unexpectedly, sequencing demonstrated exon 4 sequence corresponding to CYP2A7 in samples genotyped as CYP2A6*B2. In the population study, we found consistently low allele frequencies (

A haplotype at the DBH locus, associated with low plasma dopamine beta-hydroxylase activity, also associates with cocaine-induced paranoia.

Low levels of dopamine beta-hydroxylase (DbetaH) protein in the plasma or cerebrospinal fluid (CSF) are associated with greater vulnerability to positive psychotic symptoms in several psychiatric disorders. DbetaH level is a stable, genetically controlled trait. DBH, the locus encoding DbetaH protein, is the major quantitative trait locus controlling plasma and CSF DbetaH levels. We therefore hypothesized that DBH variants or haplotypes, associated with low levels of DbetaH in the plasma, would also associate with greater vulnerability to cocaine-induced paranoia. To test this hypothesis, we first showed that a di-allelic variant, DBH*5'-ins/del, located approximately 3 kb 5' to the DBH transcriptional start site, significantly associates with plasma DbetaH activity in European-Americans (n = 66). Linkage disequilibrium analysis of that polymorphism and DBH*444g/a, another di-allelic variant associated with DbetaH levels, demonstrated that alleles of similar association to DbetaH levels are in positive disequilibrium. We then estimated DBH haplotype frequencies in cocaine-dependent European Americans rated for cocaine-induced paranoia (n = 45). As predicted, the low-DbetaH-associated haplotype, Del-a, was significantly more frequent (P = 0.0003) in subjects endorsing cocaine-induced paranoia (n = 29) than in those denying it (n = 16). Comparison to control haplotype frequencies (n = 145 healthy European-Americans) showed that the association predominantly reflected under-representation of Del-a haplotypes in those denying cocaine-induced paranoia. We conclude that: (a) the two DBH polymorphisms we studied are associated with plasma DBH levels; (b) those two polymorphisms are in significant linkage disequilibrium in European Americans, with alleles of similar association to DbetaH levels in positive disequilibrium; and (c) the haplotype associated with low DBH activity is also associated with cocaine-induced paranoia. Molecular Psychiatry (2000) 5, 56-63.

Population studies of polymorphisms of the serotonin transporter protein gene.

The range of allele frequency variation in humans for any locus that may have functionally important genetic variation needs to be documented. Therefore, we tested two polymorphisms at the serotonin transporter protein locus (SLC6A4) in samples from seven specific populations from five continental regions. We studied the promoter polymorphism which is reported to have functional significance and to be associated with anxiety- and depression-related phenotypes [Lesch et al., 1996: Science 274:1527-1531], and the intron 2 VNTR polymorphism [Lesch et al., 1994: J Neural Transm 95:157-162]. Allele frequencies for both systems show significant global variation, and consequently so do haplotype frequencies. Linkage disequilibrium varied among the populations, being absent in some and highly significant in others. These differences further document a large potential for population stratification in association studies of either of these SLC6A4 polymorphisms.

A previously undescribed intron and extensive 5' upstream sequence, but not Phox2a-mediated transactivation, are necessary for high level cell type-specific expression of the human norepinephrine transporter gene.

The synaptic action of norepinephrine is terminated by NaCl-dependent uptake into presynaptic noradrenergic nerve endings, mediated by the norepinephrine transporter (NET). NET is expressed only in neuronal tissues that synthesize and secrete norepinephrine and in most cases is co-expressed with the norepinephrine-synthetic enzyme dopamine beta-hydroxylase (DBH). To understand the molecular mechanisms regulating human NET (hNET) gene expression, we isolated and characterized an hNET genomic clone encompassing approximately 9. 5 kilobase pairs of the 5' upstream promoter region. Here we demonstrate that the hNET gene contains an as-yet-unidentified intron of 476 base pairs within the 5'-untranslated region. Furthermore, both primer extension and 5'-rapid amplification of cDNA ends analyses identified multiple transcription start sites from mRNAs expressed only in NET-expressing cell lines. The start sites clustered in two subdomains, each preceded by a TATA-like sequence motif. As expected for mature mRNAs, transcripts from most of these sites each contained an additional G residue at the 5' position. Together, the data strongly support the authenticity of these sites as the transcriptional start sites of hNET. We assembled hNET-chloramphenicol acetyltransferase reporter constructs containing different lengths of hNET 5' sequence in the presence or the absence of the first intron. Transient transfection assays indicated that the combination of the 5' upstream sequence and the first intron supported the highest level of noradrenergic cell-specific transcription. Forced expression of the paired-like homeodomain transcription factor Phox2a did not affect hNET promoter activity in NET-negative cell lines, in marked contrast to its effect on a DBH-chloramphenicol acetyltransferase reporter construct. Together with our previous studies suggesting a critical role of Phox2a for noradrenergic-specific expression of the DBH gene, these data support a model in which distinct, or partially distinct, molecular mechanisms regulate cell-specific expression of the NET and DBH genes.

DRD2 allele frequencies and linkage disequilibria, including the -141CIns/Del promoter polymorphism, in European-American, African-American, and Japanese subjects.

Although many studies have addressed the possible association of D2 dopamine receptor (DRD2) alleles-particularly in the TaqI "A" system (with the DRD2*A1 allele)-with positive results for a range of behavioral phenotypes in populations of European origin, the interpretation of those results remains controversial; they could reflect physiological relationships between gene and phenotype, population stratification, or random variation. Since mutational analysis studies of the DRD2 gene have thus far failed to reveal a mutation that could provide a physiological basis for these results, functional meaning for them depends on linkage disequilibrium with a functional variant. A recently described functional variant in the DRD2 promoter (-141CIns/Del), which is about 250 kb 5' to the variants studied in psychiatric illness, could conceivably provide an explanation for the positive findings, if it were in linkage disequilibrium with DRD2*A1 in populations similar to those for which an association has been reported. We studied linkage disequilibrium (LD) and frequencies of haplotypes containing the DRD2*A, DRD2*D, and -141CIns/Del systems in European-Americans, African-Americans, and Japanese subjects. Although we found evidence for LD across the 250-kb first intron in both American populations, we did not find significant LD between the DRD2*A system and the -141CIns/Del system in the European-Americans. This newly described functional variant therefore does not provide a straightforward physiological explanation for previously reported genetic associations with DRD2*A1 in European-American subjects.

Dopamine beta-hydroxylase: two polymorphisms in linkage disequilibrium at the structural gene DBH associate with biochemical phenotypic variation.

Levels of the enzyme dopamine beta-hydroxylase (DbetaH) in the plasma and cerebrospinal fluid (CSF) are closely related biochemical phenotypes. Both are under strong genetic control. Linkage and association studies suggest the structural gene encoding DbetaH (locus name, DBH) is a major locus influencing plasma activity of DbetaH. This study examined relationships of DBH genotype determined at two polymorphic sites (a previously described GT repeat, referred to as the DBH STR and a single-base substitution at the 3' end of DBH exon 2, named DBH*444 g/a), to CSF levels of DbetaH protein in European-American schizophrenic patients, and to plasma DbetaH activity in European-American patients with mood or anxiety disorders. We also investigated linkage disequilibrium (LD) between the polymorphisms in the pooled samples from those European-American subjects (n=104). Alleles of DBH*444 g/a were associated with differences in mean values of CSF DbetaH levels. Alleles at both polymorphisms were associated with plasma DbetaH activity. Significant LD was observed between respective alleles with similar apparent influence on biochemical phenotype. Thus, allele A3 of the DBH STR was in positive LD with DBH*444a, and both alleles were associated with lower plasma DbetaH activity. DBH STR allele A4 was in positive LD with DBH*444 g, and both alleles were associated with higher plasma DbetaH activity. The results confirm that DBH is a major quantitative trait locus for plasma DbetaH activity, and provide the first direct evidence that DBH also influences CSF DbetaH levels. Both polymorphisms examined in this study appear to be in LD with one or more functional polymorphisms that mediate the influence of allelic variation at DBH on DbetaH biochemical phenotypic variation

Serotonin transporter protein (SLC6A4) allele and haplotype frequencies and linkage disequilibria in African- and European-American and Japanese populations and in alcohol-dependent subjects.

The SLC6A4 locus encodes the serotonin transporter, which in turn mediates the synaptic inactivation of the neurotransmitter serotonin. Two PCR-formatted polymorphisms at this locus have been described, the first of which is a variable number tandem repeat located in exon 2, and the second a repeat sequence polymorphism located in the promoter region. The latter polymorphism alters transcriptional activity of SLC6A4, and has been reported to be associated with anxiety and depression-related traits. We studied allele frequencies, and computed haplotype frequencies and linkage disequilibrium measures, for these two polymorphisms in European-American, African-American, and Japanese populations, and in a set of alcohol-dependent European-American subjects. Allele frequencies for both systems showed variation, with significant differences overall for each system, and significant differences between each pair of populations for both systems. Linkage disequilibrium also varied among the populations. There were no significant differences in allele or haplotype frequencies between the European-American population samples and alcohol-dependent subjects. The population differences demonstrate a potential for population stratification in association studies of either of these SLC6A4 polymorphisms. If genetic variation at this locus really is associated with behavioral variation, these results could reflect either different behavioral adaptations in different populations, or random genetic drift of a behaviorally important but selectively neutral polymorphism.

Ciliary neurotrophic factor null allele frequencies in schizophrenia, affective disorders, and Alzheimer's disease.

Ciliary neurotrophic factor (CNTF) is a cytokine that has been reported to affect cellular differentiation. Mouse CNTF knockouts have progressive motor neuron atrophy, but this protein has uncertain physiological function in humans. A naturally occurring CNTF variant in man, observed in many populations, abolishes function of the protein product, providing the opportunity to study loss of CNTF function in humans. It has been reported previously that this variant does not predispose to several neurological and neuropsychiatric disorders, including Alzheimer's disease, but findings have been more ambiguous with respect to other conditions, such as schizophrenia. We report here allele frequencies for this null mutation in populations diagnosed with mood disorders (unipolar depression, single episode or recurrent; N = 59), schizophrenia (N = 66), or Alzheimer's disease (N = 93). We found no association of the CNTF null with any of these phenotypes. There is presently no known phenotype consistently associated with either heterozygosity or homozygosity for the CNTF null allele, suggesting either that this protein does not serve a necessary function in humans or is redundant with some other protein or that any human phenotype associated with absence of CNTF is considerably more subtle than that seen in mouse.

Population genetics of a functional variant of the dopamine beta-hydroxylase gene (DBH).

Dopamine beta-hydroxylase (E.C. 1.14.17.1; protein abbreviation: DbetaH) catalyzes conversion of dopamine to norepinephrine. Previous work identified two expressed alleles of the gene encoding DbetaH (locus symbol DBH), containing either G or T at nucleotide position 910, resulting in specification by codon 304 of alanine (DBH*304A) or serine (DBH*304S), respectively. The current study employed denaturing gradient gel electrophoresis to identify these alleles, and after developing a PCR RFLP for rapid genotyping, estimated the frequencies of the alleles in African-Americans, European-Americans, and in several geographically dispersed populations (Mbuti, Danes, Adygei, Chinese, Japanese, Surui, Maya, and Nasioi). DBH*304A was the most common allele in all populations tested, with allele frequencies greater than 0.80 in each case. There was significant heterogeneity in allele frequency across population groups. The DBH*304S allele was most common in subjects of African descent, and least common in East Asians and individuals from indigenous populations of North and South America. The frequency of DBH*304S was significantly higher in African-Americans (0.16) than in European-Americans (0.06; P < 0.004). Of the four DBH*304S homozygotes observed, all were Europeans and three of the four were Danes. Based on empirical P-values generated by computer simulation, the observed proportions of DBH*304S homozygotes did not differ significantly from Hardy-Weinberg expectations in any of the populations after Bonferroni correction for multiple comparisons. The observation of significant heterogeneity in DBH*304S allele frequency across different population samples demonstrates the importance of controlling for population stratification in future studies testing for associations between DBH*304S and clinical phenotypes.

Inducible cAMP early repressor can modulate tyrosine hydroxylase gene expression after stimulation of cAMP synthesis.

Members of the CREB/CREM/ATF family of transcription factors either enhance or repress transcription after binding to the cAMP response elements (CREs) of numerous genes. The rat gene for tyrosine hydroxylase (TH) bears a canonical CRE, at base pairs -38 through -45 from the transcription initiation site, that is essential for basal and cAMP-stimulated transcription (Kim, K.-S., Lee, M. K., Carroll, J., and Joh, T. H. (1993) J. Biol. Chem. 268, 15689-15695; Lazaroff, M., Patankar, S., Yoon, S. O., and Chikaraishi, D. M. (1995) J. Biol. Chem. 270, 21579-21589). The current study identifies CRE-binding proteins induced in pharmacological paradigms characterized by TH activation. PC12- and rat adrenal gland-derived nuclear proteins retarded a TH-CRE oligonucleotide in gel mobility shift assays with virtually identical patterns. These differed substantially from patterns exhibited by extracts from locus ceruleus or from neuroblastoma (SK-N-BE()C) and locus ceruleus-derived (CATH.a) cell lines. Forskolin stimulation of PC12 cells and reserpine treatment of rats increased, in nuclear extracts derived from cells and adrenal glands, respectively, the amount of a fast moving CRE/protein complex that was supershifted by an anti-CREM antibody. Subsequent Western, Northern, and polymerase chain reaction analyses indicated that a specific member of the CREM family, the inducible cAMP early repressor (ICER), was strongly induced in both systems. Cotransfection of PC12 cells with TH2400CAT plasmid and the expression vector pCMV-ICER-Ib demonstrated that ICER efficiently represses the transcriptional activity of the TH gene promoter. In addition, PKA-stimulated transcriptional activity of the promoter was effectively suppressed by ICER. These results suggest that ICER can modulate cAMP-stimulated transcription of the TH gene and provide a model accounting for rapid reversal of increased TH transcription following elevations in cAMP.