Background: CYP2C9 polymorphisms are associated with decreased S-warfarin clearance and lower maintenance dosage. Decreased expression of VKORC1 resulting from the ؊1639G>A substitution has also been implicated in lower warfarin dose requirements. We investigated the additional contribution of this polymorphism to the variance in warfarin dose. Methods: Sixty-five patients with stable anticoagulation were genotyped for CYP2C9 and VKORC1 with Tag-It™ allele-specific primer extension technology. Plasma Swarfarin concentrations and warfarin maintenance dose were compared among patients on the basis of the VKORC1 ؊1639G>A genotype. Results: Eighty percent of CYP2C9*1/*1 patients stabilized on <4.0 mg/day warfarin had at least 1 VKORC1 ؊1639A allele. Mean warfarin doses (SD) were 6.7 (3.3), 4.3 (2.2), and 2.7 (1.2) mg/day for patients with the VKORC1 ؊1639GG, GA, and AA genotypes, respectively. Steady-state plasma concentrations of S-warfarin were lowest in patients with the VKORC1 ؊1639AA genotype and demonstrated a positive association with the VKORC1 ؊1639G allele copy number (trend P ‫؍‬ 0.012). A model including VKORC1 and CYP2C9 geno-

Cytochrome P-450 2C9 (CYP2C9) polymorphisms (CYP2C9*2 and CYP2C9*3) reduce the clearance of warfarin, increase the risk of bleeding, and prolong the time to stable dosing. Whether prospective use of a retrospectively developed algorithm that incorporates CYP2C9 genotype and nongenetic factors can ameliorate the propensity to bleeding and delay in achieving a stable warfarin dose is unknown. We initiated warfarin therapy in 48 orthopedic patients tailored to the following variables: CYP2C9 genotype, age, weight, height, gender, race, and use of simvastatin or amiodarone. By using pharmacogenetics-based dosing, patients with a CYP2C9 variant achieved a stable, therapeutic warfarin dose without excessive delay. However compared to those without a CYP2C9 variant, patients with a variant continued to be at increased risk (hazard ratio 3.6, 95% confidence interval 1.4-9.5, p = 0.01) for an adverse outcome (principally INR > 4), despite pharmacogenetics-based dosing. There was a linear relationship (R(2) = 0.42, p < 0.001) between the pharmacogenetics-predicted warfarin doses and the warfarin maintenance doses, prospectively validating the dosing algorithm. Prospective, perioperative pharmacogenetics-based dosing of warfarin is feasible; however, further evaluation in a randomized, controlled study is recommended.

Minor improvements in algorithms can be observed with the inclusion of ethnicity and more CYP2C9 and VKORC1 SNPs as variables. Major improvements will likely require the identification of new gene associations with warfarin dosing.

Three groups have previously performed genome scans in attention-deficit/hyperactivity disorder (ADHD); linkage to chromosome 5p13 was detected in all of the respective studies. In the current study, we performed a whole-genome scan with 102 German families with two or more offspring who currently fulfilled the diagnostic criteria for ADHD. Including subsequent fine mapping on chromosome 5p, a total of 523 markers were genotyped. The highest nonparametric multipoint LOD score of 2.59 (empirical genome-wide significance 0.1) was obtained for chromosome 5p at 17 cM (according to the Marshfield map). Subsequent analyses revealed (a) a higher LOD score of 3.37 at 39 cM for a quantitative severity score based on symptoms of inattention than for hyperactivity/impulsivity (LOD score of 1.11 at 59 cM), and (b) an HLOD of 4.75 (empirical genome-wide significance 0.001) based on a parametric model assuming dominant inheritance. The locus of the solute carrier 6A3 (SLC6A3; dopamine transporter 1; DAT1) localizes to 5p15.33; the gene has repeatedly been implicated in the etiology of ADHD. However, in our sample the DAT1 VNTR did not show association with ADHD. We additionally identified nominal evidence for linkage to chromosomes 6q, 7p, 9q, 11 q, 12q and 17p, which had also been identified in previous scans. Despite differences in ethnicity, ascertainment and phenotyping schemes, linkage results in ADHD appear remarkably consistent.

Several lines of evidence indicate an involvement of brain derived neurotrophic factor (BDNF) in body weight regulation and activity: heterozygous Bdnf knockout mice (Bdnf(+/-)) are hyperphagic, obese, and hyperactive; furthermore, central infusion of BDNF leads to severe, dose-dependent appetite suppression and weight loss in rats. We searched for the role of BDNF variants in obesity, eating disorders, and attention-deficit/hyperactivity disorder (ADHD). A mutation screen (SSCP and DHPLC) of the translated region of BDNF in 183 extremely obese children and adolescents and 187 underweight students was performed. Additionally, we genotyped two common polymorphisms (rs6265: p.V66M; c.-46C > T) in 118 patients with anorexia nervosa, 80 patients with bulimia nervosa, 88 patients with ADHD, and 96 normal weight controls. Three rare variants (c.5C > T: p.T2I; c.273G > A; c.*137A > G) and the known polymorphism (p.V66M) were identified. A role of the I2 allele in the etiology of obesity cannot be excluded. We found no association between p.V66M or the additionally genotyped variant c.-46C > T and obesity, ADHD or eating disorders. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148-7299:1/suppmat/index.html.

Attention-deficit/hyperactivity disorder (ADHD) is the most common behavioral disorder in childhood with substantial heritability. Pharmacological and molecular genetic studies as well as characterization of animal models have implicated serotonergic dysfunction in the pathophysiology of ADHD. Here, we investigated the effect of polymorphic variants in the gene of the tryptophan hydroxylase-2 (TPH2), the rate-limiting enzyme of serotonin (5-HT) synthesis in the brain, in children and adolescents with ADHD. We analyzed three single nucleotide polymorphisms (SNPs) in and downstream of the transcriptional control region of the TPH2 gene in 103 families with 225 affected children. Allelic association in families with more than one affected child was assessed using the pedigree disequilibrium test. Preferential transmissions were detected for the two SNPs in TPH2's regulatory region (rs4570625, P ¼ 0.049; rs11178997, P ¼ 0.034), but not for the third SNP in intron 2 (rs4565946, P ¼ 0.3517). Haplotype analysis revealed a strong trend of association between the regulatory region SNPs (rs4570625, rs11178997) and ADHD (P ¼ 0.064). Our results link potentially functional TPH2 variations to the pathophysiology of ADHD, and further support the relevance of 5-HT in disorders related to altered motor activity and cognitive processes. Keywords: ADHD; serotonin; TPH2; sib pairs Attention-deficit/hyperactivity disorder (ADHD) is a common syndrome first diagnosed in childhood and frequently persistent throughout adult life. Prevalence ranges between 3 and 9% dependent on the nature of the population sampled and the method of ascertainment.1,2 Although heritability estimates are consistently high, averaging around 0.8, ADHD is a genetically complex disorder characterized by multifactorial inheritance involving numerous genes of moderate effect. 2-5While an imbalance in dopaminergic neurotransmission appears to be an important factor predisposing to ADHD, interaction between the dopamine (DA) and serotonin (5-HT) systems has been implicated in both the pathophysiology of ADHD and the mechanism of action of widely used stimulant compounds. By inhibition of the dopamine transporter (DAT), which was reported to be increased in the striatum in ADHD patients, 6 methylphenidate (MPH) is highly effective in reducing the symptoms of ADHD. DAT knockout (KO) mice display a phenotype with increased locomotor activity, 7 which is reversed by MPH-induced increases in 5-HT neurotransmission. 8On the other hand, the hyperlocomotion in DAT KO mice is attenuated by the selective 5-HT reuptake inhibitor (SSRI) fluoxetine or the 5-HT precursor 5-hydroxytryptophan. 9 Early studies reported low platelet 5-HT levels in ADHD patients 10,11 and there is an extensive data base that ADHD-specific syndromal dimensions including impulsive behavior, aggressiveness and substance abuse are linked to alterations

Previously, we had reported a genome-wide scan for attention-deficit/hyperactivity disorder (ADHD) in 102 families with affected sibs of German ancestry; the highest multipoint LOD score of 4.75 was obtained on chromosome 5p13 (parametric HLOD analysis under a dominant model) near the dopamine transporter gene (DAT1). We genotyped 30 single nucleotide polymorphisms (SNPs) in this candidate gene and its 5 0 region in 329 families (including the 102 initial families) with 523 affected offspring. We found that (1) SNP rs463379 was significantly associated with ADHD upon correction for multiple testing (P = 0.0046); (2) the global P-value for association of haplotypes was significant for block two upon correction for all (n = 3) tested blocks (P = 0.0048); (3) within block two we detected a nominal P = 0.000034 for one specific marker combination. This CGC haplotype showed relative risks of 1.95 and 2.43 for heterozygous and homozygous carriers, respectively; and (4) finally, our linkage data and the genotype-IBD sharing test (GIST) suggest that genetic variation at the DAT1 locus explains our linkage peak and that rs463379 (P < 0.05) is the only SNP of the above haplotype that contributed to the linkage signal. In sum, we have accumulated evidence that genetic variation at the DAT1 locus underlies our ADHD linkage peak on chromosome 5; additionally solid association for a single SNP and a haplotype were shown. Future studies are required to assess if variation at this locus also explains other positive linkage results obtained for chromosome 5p.

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