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Biomedical subjects

D A Nielsen

Publications and source records attributed to D A Nielsen.

At least 19 recordsLinked to original sources
PubMed1999

No coding variant of the tryptophan hydroxylase gene detected in seasonal affective disorder, obsessive-compulsive disorder, anorexia nervosa, and alcoholism.

BACKGROUND: The goal of this study was to evaluate the role of genetic variation in the coding sequence of tryptophan hydroxylase (TPH) in the pathogenesis of several psychiatric diseases in which altered serotonin function has been implicated: bipolar affective disorder (BP), obsessive-compulsive disorder (OCD), anorexia nervosa (AN), seasonal affective disorder (SAD), panic disorder (PD), and alcoholism (Alc). METHODS: Ninety-three percent of the TPH coding sequence was screened by polymerase chain reaction single-strand conformation polymorphism (SSCP) for DNA sequence variations in 128 AN, 88 OCD, 72 SAD, 45 PD, and 36 BP patients and 142 normal volunteers. Also included in the screening were 61 Alc randomly selected from a Finnish alcoholic population in which an association of a TPH intron 7 polymorphism with suicidality was previously observed. Polymorphisms detected by SSCP were characterized by DNA sequencing and by allele-specific restriction enzyme digestion. Genotyping was then performed in 34 Finnish alcoholic suicide attempters. RESULTS: A rare silent mutation was identified in exon 10 and is designated T1095C. The C1095 allele was found in 1 OCD and in 2 AN subjects; all 3 individuals were heterozygous (C1095/T1095) for the variant allele. No association was observed between this TPH T1095C variant with either OCD, AN, Alc, or suicidality. CONCLUSION: These results suggest that the coding sequence of the TPH gene does not contain abundant variants, and may not play a major role in vulnerability to several psychopathologies in which reduced serotonin turnover has been implicated.

Alcoholism↗
PubMed1998

Tryptophan hydroxylase genotype is associated with impulsive-aggression measures: a preliminary study.

To assess the relationship between two phenotypes in an extremely well-characterized population of personality disorder patients-impulsive aggression and prolactin response to fenfluramine-and tryptophan hydroxylase (TPH) genotype, TPH genotype (at an intronic polymorphic site) and prolactin response to fenfluramine were assessed in 40 Caucasian patients with personality disorder. Impulsive aggression was assessed by using the Buss-Durkee Hostility Inventory (BDHI). Twenty-one male patients with the "LL" genotype had higher BDHI scores than men with the "UL" or the "UU" genotype. No relationship between genotype and prolactin response to fenfluramine was found. It was concluded that impulsive-aggressive behavior in male personality disorder patients may be associated with the TPH genotype.

Adult↗
PubMed1998

A tryptophan hydroxylase gene marker for suicidality and alcoholism.

BACKGROUND: Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the synthesis of serotonin. Low turnover rate of this monoamine neurotransmitter is associated with impaired impulse control. We previously reported that, in Finns, TPH genotype was associated with suicidality, a pathophysiological mechanism that may involve impaired impulse control. METHODS: Association and sib-pair linkage analyses of a polymorphism in intron 7 of the TPH gene with suicidality, alcoholism, and the Karolinska Scales of Personality were conducted in 804 Finnish alcoholic offenders, controls, and their relatives, in a sample that included 369 sib pairs. RESULTS: The association of the TPH 17 779C (L) allele to suicidality in impulsive offenders reported previously was replicated in a new group of Finnish offenders (P=.001, n=122). The intron 7 variant in the TPH gene showed significant evidence for linkage to suicidality (P=.006 in unaffected sib pairs), severe suicide attempts (P=.006 in unaffected sib pairs; regression: P=.01), alcoholism (P=.003 in unaffected sib-pairs; regression: P=.02), and Karolinska Scales of Personality socialization score (regression: P=.002). CONCLUSIONS: The status of the TPH A779C allele as a marker for suicidality was replicated and linkage with alcoholism and Karolinska Scales of Personality socialization score was also observed. A functional variant(s) in or close to the TPH gene may predispose individuals to suicidality and other behaviors thought to be influenced by serotonin.

Adult↗
PubMed1997

Tryptophan hydroxylase and catechol-O-methyltransferase gene polymorphisms: relationships to monoamine metabolite concentrations in CSF of healthy volunteers.

Concentrations of monoamine metabolites (MM) in lumbar cerebrospinal fluid (CSF) have been used extensively as indirect estimates of monoamine turnover in the brain. We investigated possible relationships between DNA polymorphisms in the tryptophan hydroxylase (TPH) and catechol-O-methyltransferase (COMT) genes and CSF concentrations of 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in healthy volunteers (n = 66). Lower CSF 5-HIAA levels were found in men with the TPH U allele (p = 0.005), but not in women. A similar but less significant pattern was observed for CSF HVA. No relationship was found between the TPH polymorphism and CSF MHPG. COMT genotypes did not relate significantly to MM concentrations. The results suggest that TPH genotypes participate differentially in the regulation of serotonin turnover rate under presumed steady state in the central nervous system of men. Due to the uncertain functional relevance of the DNA polymorphism investigated and the many calculations performed, the results should be interpreted with caution until replicated.

Adult↗
PubMed1997

Sequence, splice site and population frequency distribution analyses of the polymorphic human tryptophan hydroxylase intron 7.

A human tryptophan hydroxylase intron seven polymorphism previously associated with low CSF 5-HIAA and suicidal behavior was sequenced and characterized for its potential role in TPH pre-mRNA splicing. Two polymorphic sites were identified: A218C and A779C. The 779A allelic frequency in various populations ranged from 0.43 to 0.61 and was in strong linkage disequilibrium with the A218C site. A218C provides a site for restriction fragment length polymorphism analysis. TPH mRNA was reverse-transcribed and sequenced. No aberrant splice products from the 779A or 779G TPH genes were detected nor were any other polymorphic nucleotides found.

Base Sequence↗
PubMed1997

Agonist-promoted down-regulation and functional desensitization in two naturally occurring variants of the human serotonin1A receptor.

We recently reported two naturally occurring polymorphisms of the human serotonin1A (5-HT1A) receptor: glycine22-->serine (Ser22) and isoleucine28-->valine (Val28) in the putative aminoterminal domain of the receptor. To investigate the regulatory properties of these variants, the wild type (WT) and variant 5-HT1A receptors were stably expressed in CHO-K1 cells. WT, Ser22, and Val28 displayed similar high-affinity binding to [3H]-8-OH-DPAT. Competition experiments with 5-HT1A agonists and antagonists demonstrated similar pharmacological profiles. Receptor agonist-promoted down-regulation was tested by exposure to 100 mumol/L 8-OH-DPAT. After 24-h exposure, WT and Val28 underwent 59.3 +/- 3.9% and 59.5 +/- 1.4% reduction in receptor density respectively, whereas the degree of down-regulation was significantly lower for Ser22 (21.4 +/- 4.2%). Cell treatment for 24 h with 100 mumol/L 8-OH-DPAT reduced the 5-HT-induced inhibition of cAMP accumulation by 24.9 +/- 5.1% for WT and 16.4 +/- 0.8% for Val28, but only by 4.8 +/- 3% for Ser22. We conclude that the Ser22 variant is capable of attenuating agonist-mediated receptor down-regulation and desensitization.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1997

Possible association of a polymorphism of the tryptophan hydroxylase gene with suicidal behavior in depressed patients.

OBJECTIVE: This study was designed to test the hypothesis that serotonin-system-related genes may be correlated with suicide risk. METHOD: Fifty-one unrelated Caucasian inpatients with major depression, with or without a history of suicidal acts, were genotyped for a biallelic polymorphism at the tryptophan hydroxylase locus. RESULTS: The less common tryptophan hydroxylase U allele occurred with greater frequency in the patients who had attempted suicide. A logistic regression analysis confirmed an association between tryptophan hydroxylase genotype and lifetime history of suicide attempts. CONCLUSIONS: Serotonergic-system-related genes may influence the risk of suicide in persons with major depression.

Adult↗
PubMed1996

Limitations imposed by heteroduplex formation on quantitative RT-PCR.

RT-PCR, a rapidly emerging technique for the detection of RNA, is being used by many investigators to quantify small amounts of RNA. Accurate quantification of RNA content has been facilitated by the use of competitive amplicons as internal controls. We demonstrate that losses in sensitivity and accuracy are associated with an internal standard having sequence similarity to the primary amplicon. Analysis of PCR products under non-denaturing and denaturing conditions provided evidence that these losses were associated with heteroduplex formation. Subsequent analysis of factors associated with heteroduplex formation provides insights for future development of competitive assays. Assay considerations that can minimize limitations associated with competitive PCR protocols are discussed.

Animals↗
PubMed1996

Isolation and characterization of murine vav2, a member of the vav family of proto-oncogenes.

We describe the isolation and characterization of a cDNA encoding murine vav2. vav2 shares 63% and 55% identity at the nucleic acid and amino acid levels, respectively, with vav, a proto-oncogene that plays an essential role in embryonic development and hematopoietic signal transduction. The 100 kDa Vav2 protein contains the characteristic array of structural motifs found in Vav. However, unlike vav, vav2 transcripts are widely distributed in both hematopoietic and non-hematopoietic tissues. In the adult, vav2 mRNA is found at high levels in the spleen, liver, testes and placenta. Northern blot analysis reveals two vav2 mRNA species (designated alpha and beta). The alpha species is expressed throughout development while the alpha and beta species are expressed tissue-specifically in adults. Transfection of NIH3T3 cells with expression vectors containing vav2 deletions demonstrate that elimination of 183 amino terminal residues of Vav2 is sufficient to activate its oncogenic potential. Vav2-induced transformation is characterized by the appearance of foci composed of cells in which cytokinesis and karyokinesis are uncoupled. This phenotype is comparable, but not identical, to morphological changes induced by Vav and other members of the DbI family of oncoproteins. Our results suggest that Vav family members mediate functions important in the regulation of cell architecture and proliferation in most, if not all, tissues.

3T3 Cells↗
PubMed1995

Antisense oligonucleotide inhibition of tryptophan hydroxylase activity in mouse brain.

To examine in vivo effectiveness of antisense oligonucleotides against tryptophan hydroxylase (TPH) mRNA, adult male swiss-NIH mice were implanted with in-dwelling cannula into the 4th ventricle and after recovery infused with either antisense oligonucleotide to TPH, scrambled control oligo or saline vehicle for four consecutive days. An additional group of animals bearing cannula were injected a single time i.p. with the TPH inhibitor para-chlorophenylalanine (PCPA; 300 mg/kg). All animals were sacrificed on the afternoon of the 4th day of treatment. TPH activity was measured by enzymatic assay and HPLC quantification of end-product synthesis. There was a significant decrease (> 50%) in TPH activity in both the PCPA-treated and antisense-oligo infused animals compared to either scrambled-oligo or saline-infused subjects (ANOVA; P < 0.05). There was no difference between saline and scrambled oligo-infusion. In a separate group of animals treated in the same way, behavioral tests were conducted on the afternoon of the 4th day. Two tests of anxiety, the hole-board apparatus and the elevated plus-maze, indicated some significant effects of PCPA treatment and/or antisense oligo-infusion but confounding effects due to alterations in locomotion could not be ruled out. However, tests on a rotorod apparatus indicated that antisense oligo-infused animals retained good balance and coordination in that their performance significantly improved on the second test, as did that of scrambled-oligo infused animals. In contrast, PCPA-treated animals did not improve, suggesting that locomotor performance had been impaired. These data support the notion that antisense oligo blockade may offer advantages over pharmacological manipulations of enzyme activity.

Analysis of Variance↗
PubMed1995

SSCP primer design based on single-strand DNA structure predicted by a DNA folding program.

To predict alterations in single-strand DNA mobility in non-denaturing electrophoretic gels, Zuker's RNA folding program was modified. Energy files utilized by the LRNA RNA folding algorithm were modified to emulate folding of single-strand DNA. Energy files were modified to disallow G-T base pairing. Stacking energies were corrected for DNA thermodynamics. Constraints on loop nucleotide sequences were removed. The LRNA RNA folding algorithm using the DNA fold energy files was applied to predict folding of PCR generated single-strand DNA molecules from polymorphic human ALDH2 and TPH alleles. The DNA-Fold version 1.0 program was used to design primers to create and abolish SSCP mobility shifts. Primers were made that add a 5' tag sequence or alter complementarity to an internal sequence. Differences in DNA secondary structure were assessed by SSCP analysis and compared to single-strand DNA secondary structure predictions. Results demonstrate that alterations in single-strand DNA conformation may be predicted using DNA-Fold 1.0.

Aldehyde Dehydrogenase↗
PubMed1995

Two naturally occurring amino acid substitutions in the human 5-HT1A receptor: glycine 22 to serine 22 and isoleucine 28 to valine 28.

The human 5-HT1A receptor was screened for naturally occurring mutations. The PCR product of the 5-HT1A receptor gene was digested with several restriction enzymes and evaluated by single-strand conformational polymorphism (SSCP) analysis. Comparison of the SSCP electrophoretic pattern with a restriction map of the 5-HT1A receptor allowed localization of the polymorphic sites facilitating their identification by sequence analysis. Two polymorphisms were identified in the human 5-HT1A receptor gene that altered amino acid composition. The polymorphisms encode amino acid substitutions in the 5-HT1A receptor of a glycine to serine at amino acid 22 and an isoleucine to valine at amino acid 28, respectively. Both polymorphisms alter the extracellular amino terminal domain of the 5-HT1A receptor. The polymorphic 5-HT1A alleles have been found in American and Finnish Caucasians and in native American Indians. This is the first report of a polymorphism in the human 5-HT1A receptor gene that alters the structure of the 5-HT1A receptor protein composition.

Alleles↗
PubMed1995

Low brain serotonin turnover rate (low CSF 5-HIAA) and impulsive violence.

The findings of a series of studies by the authors support the idea that most impulsive offenders who have a tendency to behave aggressively while intoxicated have a low brain serotonin turnover rate. The impulsive violent offenders with the lowest CSF 5-HIAA concentrations have diurnal activity rhythm disturbances, and are also prone to hypoglycemia after an oral glucose challenge. Low CSF 5-HIAA combined with hyoglycemic tendency also predicts future violence under the influence of alcohol. Sons of alcoholic fathers, who have committed violent crimes, have very low CSF 5-HIAA concentrations. Vagal tone does not correlate significantly with CSF 5-HIAA but correlates with enhanced insulin secretion, which is most prominent in subjects with intermittent explosive disorder. A polymorphism of tryptophan hydroxylase (TPH) gene is associated with low CSF 5-HIAA and a history of suicide attempts.

Alcoholism↗
PubMed1994

Suicidality and 5-hydroxyindoleacetic acid concentration associated with a tryptophan hydroxylase polymorphism.

BACKGROUND: To examine whether the tryptophan hydroxylase (TPH) gene, which codes for the rate-limiting enzyme in the biosynthesis of serotonin, may be a factor influencing serotonin turnover and behaviors controlled by serotonin. METHODS: Using a polymerase chain reaction-based method, TPH genotype was determined in DNA samples from 56 impulsive and 14 nonimpulsive, alcoholic, violent offenders and 20 healthy volunteers. RESULTS: In the behaviorally extreme impulsive group, we observed a significant association between TPH genotype and cerebrospinal fluid 5-hydroxyindoleacetic acid (5-HIAA) concentration. No association of TPH genotype with impulsive behavior was detected. The polymorphism was also associated with a history of suicide attempts in all violent offenders, independent of impulsivity status and cerebrospinal fluid 5-HIAA concentration. CONCLUSION: In some individuals, a genetic variant of the TPH gene may influence 5-HIAA concentration in the cerebrospinal fluid and predisposition to suicidal behavior.

Adult↗
PubMed1992

Genetic mapping of the human tryptophan hydroxylase gene on chromosome 11, using an intronic conformational polymorphism.

The identification of polymorphic alleles at loci coding for functional genes is crucial for genetic association and linkage studies. Since the tryptophan hydroxylase (TPH) gene codes for the rate-limiting enzyme in the biosynthesis of the neurotransmitter serotonin, it would be advantageous to identify a polymorphism in this gene. By examining introns of the human TPH gene by PCR amplification and analysis by the single-strand conformational polymorphism (SSCP) technique, an SSCP was revealed with two alleles that occur with frequencies of .40 and .60 in unrelated Caucasians. DNAs from 24 informative CEPH families were typed for the TPH intron polymorphism and analyzed with respect to 10 linked markers on chromosome 11, between p13 and p15, with the result that TPH was placed between D11S151 and D11S134. This region contains loci for several important genes, including those for Beckwith-Wiedemann syndrome and tyrosine hydroxylase.

Animals↗
PubMed1990

Estradiol and estrogen receptor-dependent stabilization of a minivitellogenin mRNA lacking 5,100 nucleotides of coding sequence.

We have developed a transfection assay to investigate the estrogen-mediated stabilization of cytoplasmic vitellogenin mRNA. A minivitellogenin (MV5) gene containing the 5' and 3' untranslated and coding regions but lacking 5,075 nucleotides of internal coding sequence was constructed. Cotransfection of the MV5 plasmid and a Xenopus estrogen receptor expression plasmid into Xenopus liver tissue culture cells yielded a 529-nucleotide MV5 mRNA, which was specifically stabilized by estrogen. MV5 mRNA exhibited the increased stability indicative of positive regulation when the estradiol-estrogen receptor complex was present and was not destabilized by unliganded estrogen receptor. Transfected estrogen receptor, estradiol, and 529 nucleotides of the 5,604-nucleotide vitellogenin B1 mRNA were sufficient for stabilization.

Animals↗