Diversity Outbred Mice Identify Population-Based Exposure Thresholds and Genetic Factors that Influence Benzene-Induced Genotoxicity.

BACKGROUND: Inhalation of benzene at levels below the current exposure limit values leads to hematotoxicity in occupationally exposed workers. OBJECTIVE: We sought to evaluate Diversity Outbred (DO) mice as a tool for exposure threshold assessment and to identify genetic factors that influence benzene-induced genotoxicity. METHODS: We exposed male DO mice to benzene (0, 1, 10, or 100 ppm; 75 mice/exposure group) via inhalation for 28 days (6 hr/day for 5 days/week). The study was repeated using two independent cohorts of 300 animals each. We measured micronuclei frequency in reticulocytes from peripheral blood and bone marrow and applied benchmark concentration modeling to estimate exposure thresholds. We genotyped the mice and performed linkage analysis. RESULTS: We observed a dose-dependent increase in benzene-induced chromosomal damage and estimated a benchmark concentration limit of 0.205 ppm benzene using DO mice. This estimate is an order of magnitude below the value estimated using B6C3F1 mice. We identified a locus on Chr 10 (31.87 Mb) that contained a pair of overexpressed sulfotransferases that were inversely correlated with genotoxicity. CONCLUSIONS: The genetically diverse DO mice provided a reproducible response to benzene exposure. The DO mice display interindividual variation in toxicity response and, as such, may more accurately reflect the range of response that is observed in human populations. Studies using DO mice can localize genetic associations with high precision. The identification of sulfotransferases as candidate genes suggests that DO mice may provide additional insight into benzene-induced genotoxicity.

Identification of QTLs with main, epistatic and QTL × environment interaction effects for salt tolerance in rice seedlings under different salinity conditions.

Salt tolerance of rice (Oryza sativa L.) at the seedling stage is one of the major determinants of its stable establishment in saline soil. One population of recombinant inbred lines (RILs, F (2:9)) derived from a cross between the salt-tolerant variety Jiucaiqing and the salt-sensitive variety IR26 was used to determine the genetic mechanism of four salt tolerance indices, seedling height (SH), dry shoot weight (DSW), dry root weight (DRW) and Na/K ratios (Na/K) in roots after 10 days in three salt concentrations (0.0, 0.5 and 0.7 % NaCl). The main effect QTLs (M-QTLs) and epistatic QTLs (E-QTLs) were detected by QTL IciMapping program using single environment phenotypic values. Eleven M-QTLs and 11 E-QTLs were identified for the salt tolerance indices. There were six M-QTLs and two E-QTLs identified for SH, three M-QTLs and five E-QTLs identified for DSW, two M-QTLs and one E-QTL identified for DRW, and three E-QTLs identified for Na/K. The phenotypic variation explained by each M-QTL and E-QTL ranged from 7.8 to 23.9 % and 13.3 to 73.7 %, respectively. The QTL-by-environment interactions were detected by QTLNetwork program in the joint analyses of multi-environment phenotypic values. Six M-QTLs and five E-QTLs were identified. The phenotypic variation explained by each QTL and QTL × environment interaction ranged from 0.95 to 6.90 % and 0.02 to 0.50 %, respectively. By comparing chromosomal positions of these M-QTLs with those previously identified, five M-QTLs qSH1.3, qSH12.1, qSH12.2, qDSW12.1 and qDRW11 might represent novel salt tolerance genes. Five selected RILs with high salt tolerance had six to eight positive alleles of the M-QTLs, indicating that pyramiding by marker-assisted selection (MAS) of M-QTLs can be applied in rice salt tolerance breeding programs.

Microcephaly with simplified gyration, epilepsy, and infantile diabetes linked to inappropriate apoptosis of neural progenitors.

We describe a syndrome of primary microcephaly with simplified gyral pattern in combination with severe infantile epileptic encephalopathy and early-onset permanent diabetes in two unrelated consanguineous families with at least three affected children. Linkage analysis revealed a region on chromosome 18 with a significant LOD score of 4.3. In this area, two homozygous nonconserved missense mutations in immediate early response 3 interacting protein 1 (IER3IP1) were found in patients from both families. IER3IP1 is highly expressed in the fetal brain cortex and fetal pancreas and is thought to be involved in endoplasmic reticulum stress response. We reported one of these families previously in a paper on Wolcott-Rallison syndrome (WRS). WRS is characterized by increased apoptotic cell death as part of an uncontrolled unfolded protein response. Increased apoptosis has been shown to be a cause of microcephaly in animal models. An autopsy specimen from one patient showed increased apoptosis in the cerebral cortex and pancreas beta cells, implicating premature cell death as the pathogenetic mechanism. Both patient fibroblasts and control fibroblasts treated with siRNA specific for IER3IP1 showed an increased susceptibility to apoptotic cell death under stress conditions in comparison to controls. This directly implicates IER3IP1 in the regulation of cell survival. Identification of IER3IP1 mutations sheds light on the mechanisms of brain development and on the pathogenesis of infantile epilepsy and early-onset permanent diabetes.

Identification and replication of loci involved in camptothecin-induced cytotoxicity using CEPH pedigrees.

To date, the Centre d'Etude Polymorphism Humain (CEPH) cell line model has only been used as a pharmacogenomic tool to evaluate which genes are responsible for the disparity in response to a single drug. The purpose of this study was demonstrate the model's ability to establish a specific pattern of quantitative trait loci (QTL) related to a shared mechanism for multiple structurally related drugs, the camptothecins, which are Topoisomerase 1 inhibitors. A simultaneous screen of six camptothecin analogues for in vitro sensitivity in the CEPH cell lines resulted in cytotoxicity profiles and orders of potency which were in agreement with the literature. For all camptothecins studied, heritability estimates for cytotoxic response averaged 23.1 ± 2.6%. Nonparametric linkage analysis was used to identify a relationship between genetic markers and response to the camptothecins. Ten QTLs on chromosomes 1, 3, 5, 6, 11, 12, 16 and 20 were identified as shared by all six camptothecin analogues. In a separate validation experiment, nine of the ten QTLs were replicated at the significant and suggestive levels using three additional camptothecin analogues. To further refine this list of QTLs, another validation study was undertaken and seven of the nine QTLs were independently replicated for all nine camptothecin analogues. This is the first study using the CEPH cell lines that demonstrates that a specific pattern of QTLs could be established for a class of drugs which share a mechanism of action. Moreover, it is the first study to report replication of linkage results for drug-induced cytotoxicity using this model. The QTLs, which have been identified as shared by all camptothecins and replicated across multiple datasets, are of considerable interest; they harbor genes related to the shared mechanism of action for the camptothecins, which are responsible for variation in response.

Linkage mapping and comparative genomics using next-generation RAD sequencing of a non-model organism.

Restriction-site associated DNA (RAD) sequencing is a powerful new method for targeted sequencing across the genomes of many individuals. This approach has broad potential for genetic analysis of non-model organisms including genotype-phenotype association mapping, phylogeography, population genetics and scaffolding genome assemblies through linkage mapping. We constructed a RAD library using genomic DNA from a Plutella xylostella (diamondback moth) backcross that segregated for resistance to the insecticide spinosad. Sequencing of 24 individuals was performed on a single Illumina GAIIx lane (51 base paired-end reads). Taking advantage of the lack of crossing over in homologous chromosomes in female Lepidoptera, 3,177 maternally inherited RAD alleles were assigned to the 31 chromosomes, enabling identification of the spinosad resistance and W/Z sex chromosomes. Paired-end reads for each RAD allele were assembled into contigs and compared to the genome of Bombyx mori (n = 28) using BLAST, revealing 28 homologous matches plus 3 expected fusion/breakage events which account for the difference in chromosome number. A genome-wide linkage map (1292 cM) was inferred with 2,878 segregating RAD alleles inherited from the backcross father, producing chromosome and location specific sequenced RAD markers. Here we have used RAD sequencing to construct a genetic linkage map de novo for an organism that has no previous genome data. Comparative analysis of P. xyloxtella linkage groups with B. mori chromosomes shows for the first time, genetic synteny appears common beyond the Macrolepidoptera. RAD sequencing is a powerful system capable of rapidly generating chromosome specific data for non-model organisms.

The Arabidopsis transcription factor LUH/MUM1 is required for extrusion of seed coat mucilage.

During differentiation, the Arabidopsis (Arabidopsis thaliana) seed coat epidermal cells secrete mucilage composed primarily of rhamnogalacturonan I that is extruded from the seed coat upon imbibition. The mucilage of the mucilage modified1 (mum1) mutant contains rhamnogalacturonan I that is more highly branched and lacks the ability to be extruded when exposed to water. Our cloning of the MUM1 gene shows that it encodes a putative transcription factor, LEUNIG_HOMOLOG (LUH). Cellular localization and transcriptional assay results suggest that LUH/MUM1 is a nucleus-localized transcriptional activator. LUH/MUM1 is expressed in all the tissues examined, including the seed coat. Quantitative reverse transcription-polymerase chain reaction data suggest that LUH/MUM1 is expressed throughout seed coat development, reaching peak expression late in differentiation. LUH1/MUM1 expression in plants homozygous for mutations in several genes encoding regulators of seed coat mucilage was unchanged. Thus, LUH/MUM1 expression appears to be independent of other transcription factors known to regulate aspects of seed coat mucilage biology. The expression in the luh/mum1 mutant of three genes encoding enzymes needed for mucilage extrusion, MUM2, SUBSILIN PROTEASE1.7, and ß-XYLOSIDASE1, was reduced relative to that of the wild type. Overexpression of MUM2 could partially rescue the mum1 phenotype. These data suggest that LUH/MUM1 is a positive regulator of all three genes.

The genetic control of tolerance to aluminum toxicity in the 'Essex' by 'Forrest' recombinant inbred line population.

Aluminum (Al) toxicity to plant roots is a major problem of acidic soils. The main chemical reaction involved is Al hydrolysis. Application of lime or nitrate fertilizers to raise soil pH reduces Al toxicity but not as economically as a plant genotypes with natural tolerance against this stress. Ammonium fertilization of crops and assimilation of ammonium (even that derived from dinitrogen) are particularly acidifying of the root zone. The aims of the present study were to find genotypes of soybean tolerant to aluminum stress and identify QTL underlying that trait. Used were recombinant inbred lines (RILs) derived from the cross of 'Essex' by 'Forrest'. RILs were grown in a greenhouse for 3 weeks and then transferred to hydroponics in a growth chamber. Root lengths (RL) were measured before and 72 h after Al treatment. RL before and after Al treatment were measured and used to calculate root tolerance index (RTI) and relative mean growth (RMG). RILs 1, 85, 40 and 83 had significant (P<0.005) tolerance to Al stress judged by RL after Al, RTI and RMG. Eleven minor but significant marker-trait associations (P<0.05) were detected using one-way ANOVA but only two major loci were significant in composite interval maps (LOD>3.0). The QTL on linkage group F (chromosome 13) was in the interval Satt160-Satt252 with a peak at 24 cM (peak LOD was 3.3). The QTL underlay 31% of trait variation and the Essex allele provided an additional 1.61 cm of root growth over 72 h in the presence of Al. The QTL on linkage group C2 (probably chromosome 4) was in the interval from Satt202 to Satt371 with a peak at 3.2 cM (peak LOD was 14.7). The QTL underlay 34% of trait variation or 1.81 cm of growth over 72 h in the presence of Al. Both loci encompassed genes implicated in citrate metabolism, a method of aluminum detoxification known to vary among soybean cultivars. Two major loci and at least nine minor loci were inferred to underlie tolerance to Al. RILs and markers may be used to select alleles that increase tolerance to soybean against Al stress.

Identification and analysis of the germin-like gene family in soybean.

BACKGROUND: Germin and germin-like proteins constitute a ubiquitous family of plant proteins. A role of some family members in defense against pathogen attack had been proposed based on gene regulation studies and transgenic approaches. Soybean (G. max L. Merr.) germin genes had not been characterized at the molecular and functional levels. RESULTS: In the present study, twenty-one germin gene members in soybean cultivar 'Maple Arrow' (partial resistance to Sclerotinia stem rot of soybean) were identified by in silico identification and RACE method (GmGER 1 to GmGER 21). A genome-wide analyses of these germin-like protein genes using a bioinformatics approach showed that the genes located on chromosomes 8, 1, 15, 20, 16, 19, 7, 3 and 10, on which more disease-resistant genes were located on. Sequence comparison revealed that the genes encoded three germin-like domains. The phylogenetic relationships and functional diversity of the germin gene family of soybean were analyzed among diverse genera. The expression of the GmGER genes treated with exogenous IAA suggested that GmGER genes might be regulated by auxin. Transgenic tobacco that expressed the GmGER 15 [corrected] gene exhibited high tolerance to the salt stress. In addition, the GmGER mRNA increased transiently at darkness and peaked at a time that corresponded approximately to the critical night length. The mRNA did not accumulate significantly under the constant light condition, and did not change greatly under the SD and LD treatments. CONCLUSIONS: This study provides a complex overview of the GmGER genes in soybean. Phylogenetic analysis suggested that the germin and germin-like genes of the plant species that had been founded might be evolved by independent gene duplication events. The experiment indicated that germin genes exhibited diverse expression patterns during soybean development. The different time courses of the mRNAs accumulation of GmGER genes in soybean leaves appeared to have a regular photoperiodic reaction in darkness. Also the GmGER genes were proved to response to abiotic stress (such as auxin and salt), suggesting that these paralogous genes were likely involved in complex biological processes in soybean.

Characterization and linkage mapping of an ENU-induced mutant mouse with defective spermatogenesis.

repro23 is an autosomal recessive mutation of the mouse generated by the N-ethyl-N-nitrosourea (ENU)-induced mutagenesis program at The Jackson Laboratory. The repro23/repro23 homozygous mouse shows male-specific infertility caused by defective spermatogenesis. In the present study, we investigated the testicular pathology of the affected mouse and performed linkage analysis to determine the chromosomal localization of the repro23 locus. Histological examination of the affected testis showed that the seminiferous epithelium of the repro23/repro23 mice contained spermatogonia and early stage spermatocytes, but no spermatids or spermatozoa. Immunohistochemical staining for Hsc70t, a spermatid specific protein, confirmed the absence of elongating spermatids. These findings indicated interruption of the spermatogenesis during meiosis in the repro23/repro23 mouse. By linkage analysis using 137 affected mice of F(2) progeny obtained from crosses between repro23/repro23 female and JF1/Ms (+/+) male mice, the repro23 locus was mapped to 2.2-Mb region of mouse chromosome 7. Although this region contains several potential candidate genes for the repro23 mutation, no gene already identified as a cause of defective spermatogenesis was in this region. Therefore, the gene responsible for the repro23 mutation is suggested to be a novel gene which plays an essential role in mammalian spermatogenesis.

Influence of TAAR6 polymorphisms on response to aripiprazole.

BACKGROUND: There is some evidence suggesting a role of TAAR6 in schizophrenia. The aim of the present study is to investigate possible influences of a panel of markers in TAAR6 (rs8192625, rs4305745, rs4305746, rs6903874, rs6937506) on clinical outcomes and side effects in a sample of Korean schizophrenic aripiprazole treated patients. METHODS: Efficacy was assessed at baseline and weeks 1, 2, 4, 6, 8 using CGI-S, CGI-I, BPRS and SANS. Side effects were evaluated through SAS, BAS and AIMS. Multivariate analysis of covariance (MANCOVA) was used to test possible influences of single SNPs on clinical and safety scores. Tests for associations using multi-marker haplotypes were performed using the statistics environment "R". RESULTS: A significant time per genotype interaction was found between rs4305746 in repeated measures of ANOVA on BPRS scores (F=2.45, df=10,365, p=0.008). In particular G/A and A/A genotype patients were more likely to improve over time as compared to carriers of the G/G genotype. Permutation analysis confirmed a significant effect of rs4305746 on course of BPRS scores over time (p=0.007). Haplotype analysis did not reveal any significant association with clinical and safety scores at any time. CONCLUSION: A possible association could exist between some genotypes in TAAR6 and response to aripiprazole. However, several limitations characterize the present work, such as small sample size, the finding related to a single scale and the possibility of false positive findings, thus further investigation is required.

Mapping quantitative trait loci associated with aluminum toxin tolerance in NJRIKY recombinant inbred line population of soybean (Glycine max).

To investigate the genetic mechanism of Al-tolerance in soybean, a recombinant inbred line population (RIL) with 184 F(2:7:11) lines derived from the cross of Kefeng No.1 x Nannong 1138-2 (Al-tolerant x Al-sensitive) were tested in pot experiment with sand culture medium in net room in Nanjing. Four traits, i.e. plant height, number of leaves, shoot dry weight and root dry weight at seedling stage, were evaluated and used to calculate the average membership index (FAi) as the indicator of Al-tolerance. The composite interval mapping (CIM) under WinQTL Cartographer v. 2.5 detected five QTLs (i.e. qFAi-1, qFAi-2, qFAi-3, qFAi-4 and qFAi-5), explaining 5.20%-9.07% of the total phenotypic variation individually. While with the multiple interval mapping (MIM) of the same software, five QTLs (qFAi-1, qFAi-5, qFAi-6, qFAi-7, and qFAi-8) explaining 5.7%-24.60% of the total phenotypic variation individually were mapped. Here qFAi-1 and qFAi-5 were detected by both CIM and MIM with the locations in a same flanking marker region, GMKF046-GMKF080 on B1 and satt278-sat_95 on L, respectively. While qFAi-2 under CIM and qFAi-6 under MIM both on D1b2 were located in neighboring regions with their confidence intervals overlapped and might be the same locus. Segregation analysis under major gene plus polygene inheritance model showed that Al-tolerance was controlled by two major genes (h(2) (mg) = 33.05%) plus polygenes (h(2) (pg) = 52.73%). Both QTL mapping and segregation analysis confirmed two QTLs responsible for Al-tolerance with relatively low heritability, and there might be a third QTL, confounded with the polygenes in segregation analysis.

Association between a frequent allele of the gene encoding OATP1B1 and enhanced LDL-lowering response to fluvastatin therapy.

INTRODUCTION: Marked lowering of low-density-lipoprotein cholesterol (LDL-C) levels (< or =50%) with intensive statin therapy is associated with major reduction in cardiovascular risk, but is limited by a potential increase in adverse effects, thereby justifying optimization of LDL-C reduction with minimal risk. The organic anion transporting polypeptide-1B1 encoded by the SLCO1B1 gene is implicated as a major transporter in cellular uptake of statins, and notably fluvastatin. We postulated that genetic variation in SLCO1B1 might affect statin bioavailability, and might therefore influence drug response and potential adverse effects. MATERIALS & METHODS: Elderly hypercholesterolemic subjects (n = 724), whose plasma lipid profile was determined before and 2 months after fluvastatin extended-release treatment (80 mg/day, n = 420), or placebo (n = 304), were genotyped for the most frequent nonsynonymous polymorphisms (SNP) in the SLCO1B1 gene (c.388A>G, c.463C>A and c.521T>C). RESULTS: Due to linkage disequilibrium, only four alleles (*1b, *5, *14 and *15) of SLCO1B1 were detected in addition to the wild-type allele (*1a). The c.463A genotype, which was systematically associated with the c.388G SNP corresponding to the *14 allele was significantly associated with percentage LDL-C reduction from baseline (p = 0.005) and with mean post-treatment LDL-C values (p = 0.0005). Subjects homozygous for the c.463C genotype (n = 294) exhibited significantly less LDL-C reduction and higher post-treatment LDL-C levels (-31.5%, 138 mg/dl) relative to heterozygous C/A patients (-36.2%, 126 mg/dl; n = 111), and to homozygous A/A subjects (-41%, 115 mg/dl; n = 15). CONCLUSIONS: These results reveal that OATP1B1 is implicated in the pharmacological action and efficacy of fluvastatin. Indeed, the common *14 allele, which is distinguished by the presence of the c.463C>A polymorphism, was associated with enhanced lipid-lowering efficacy in this study.

Genetic variation in the dopamine pathway and smoking cessation.

Twin and family studies have established that genetic factors account for much of the variation in tobacco dependence. Therefore, identification of genetic variants predictive of successful smoking cessation has implications for the future prospect of personalized smoking cessation therapies. Converging data implicate the dopamine pathway as an important neural substrate for tobacco dependence. Several candidate genes within the dopamine pathway (e.g., DRD2 and COMT) have been reported to be associated with the efficacy of bupropion and nicotine replacement therapy, and others (e.g., SLC6A3 and DRD4) have been reported to be associated with smoking cessation independent of pharmacotherapy. However, few of these candidate genes are present within regions of suggestive or significant linkage or overlap with genome-wide linkage or association studies of tobacco dependence or smoking cessation. Future studies should seek to replicate genome-wide association analyses with individual-level genotyping, and use better-defined smoking cessation phenotypes. Once robust evidence for association is established, which may take several more years, further research into the likely cost-effectiveness, feasibility and acceptability of personalized medicine for smoking cessation will be necessary before it can be translated into practice.

Genetic correlates of olanzapine-induced weight gain in schizophrenia subjects from north India: role of metabolic pathway genes.

AIM: Olanzapine is an efficacious drug often used as a first-line medication in the treatment for schizophrenia. However, weight gain is a notable adverse drug reaction of this medication in a proportion of patients and a major cause of noncompliance. Several hypotheses, including a contribution from hormonal, physiological and environmental factors, have been postulated. In this study, we aimed to analyze a possible association of genetic polymorphisms at four important candidate genes involved in appetite regulation and antipsychotic-induced metabolic syndrome with olanzapine-induced weight gain. MATERIALS & METHODS: A total of 154 schizophrenia subjects were recruited in a systematic, 6-week, open-label trial of olanzapine. We investigated the contribution of 14 polymorphisms from four genes, namely, leptin, lipoprotein lipase, tri-acyl-glycerol lipase and citrate lyase using a binary logistic regression analysis towards olanzapine-induced weight gain. RESULTS: rs 4731426 C/G SNP, a variant in the leptin gene, was moderately associated with median weight gain (Delta weight(m); [p = 0.05; OR: 2.2; 95% CI: 0.99-4.90]) and significantly associated with extreme weight gain (Delta weight(e) [p = 0.019; OR: 11.43; 95% CI: 1.49-87.55]) when average drug dose was included in a regression model. Using in silico analysis, we found that this associated intronic SNP in the leptin gene alters the binding of zinc finger 5, a transcription factor. CONCLUSION: The leptin gene may be a promising candidate for olanzapine-induced weight gain. As the associations are modest, replicate studies are warranted. This approach may facilitate rationalized drug regimens.

Clozapine-induced agranulocytosis and its genetic determinants.

Clozapine-induced agranulocytosis (CiA) is a potentially life-threatening pharmacological adverse drug reaction, which limits a broader application of this highly effective atypical antipsychotic in schizophrenic patients. Although this adverse reaction has been well known for almost 30 years, only few genetically based determinants can be identified to date. Furthermore, owing to rare occurrence, specific clinical course and complexity of pathomechanisms of antipsychotic-induced agranulocytosis, only a few of the findings met the criteria of replication. The most promising susceptibility genes for CiA include genes involved in the human leukocyte antigen system and in specific metabolizing enzyme systems. However, complex idiosyncratic drug reactions such as CiA are considered to be determined by multiple, possibly interacting genetic variations, rather than by a single causative variant.

MDR1 genotypes do not influence the absorption of a single oral dose of 600 mg valacyclovir in healthy Chinese Han ethnic males.

AIMS: To investigate the influence of three single nucleotide polymorphisms (SNPs) in exon 12 (C1236T), exon 21 (G2677T/A) and exon 26 (C3435T) of MDR1 gene on the absorption of valacyclovir after a single oral administration in the Chinese Han ethnic population. METHODS: Two hundred healthy Chinese subjects were genotyped for the SNPs of C1236T, G2677T/A and C3435T in the MDR1 gene using allele-specific polymerase chain reaction. Linkage disequilibrium (LD) was analysed. Twenty-four subjects derived from a large random sample (n = 200) received a single oral dose of 600 mg valacyclovir. Plasma concentrations of acyclovir were determined up to 14 h after administration to obtain a pharmacokinetic profile. RESULTS: LD existed between G2677T/A in exon 21 and C3435T in exon 26 (P < 0.001), between C1236T in exon 12 and C3435T (P < 0.001), but not between C1236T and G2677T/A (P > 0.05). C(max), AUC(0-1.5 h) and AUC(0-infinity) were used as indices of valacyclovir absorption. AUC(0-infinity) for the 2677TA genotype was 17.45 +/- 2.40 microg x h/ml, which was much higher compared with the 2677GG, GA and TT genotypes of 10.44 +/- 1.00, 11.84 +/- 2.83, 11.34 +/- 2.32 microg x h/ml, respectively (P < 0.05). Similarly, a statistically significant difference of AUC(0-infinity) was also observed for different linked genotypes at position 2677 vs. 3435, and 1236 vs. 3435 (P < 0.05). However, there was no significant difference in valacyclovir absorptive pharmacokinetics between carriers and noncarriers of different haplotypes (P > 0.05). CONCLUSIONS: Three SNPs of MDR1 gene did not influence the absorption of a single oral dose of 600 mg valacyclovir in healthy Chinese Han ethnic subjects.

A suppressor screen in chlamydomonas identifies novel components of the retinoblastoma tumor suppressor pathway.

The retinoblastoma (RB) protein is a eukaryotic tumor suppressor and negative cell-cycle regulator. Chlamydomonas reinhardtii cells that lack the RB homolog MAT3 show loss of size checkpoint control and deregulated cell-cycle progression leading to the production of tiny cells. We carried out an insertional mutagenesis screen to isolate bypass suppressors of mat3 (smt mutants) that reverted the mat3 cell-size defect. Previously we reported that the loci encoding Chlamydomonas homologs of E2F and DP were frequently disrupted in this screen, indicating that the architecture of the canonical RB pathway is conserved in Chlamydomonas with MAT3/RB acting as a negative regulator upstream of E2F/DP. Here, we describe four novel smt mutants that moderately suppressed the cell-size checkpoint and cell-cycle phenotypes of mat3. As single mutants, three of the smt strains displayed no obvious phenotypes, and one had a slightly small phenotype. Strikingly, several smt double-mutant combinations synergized to cause enhanced suppression of mat3 and even to cause a large-cell phenotype that is comparable to that caused by loss of DP1. Molecular characterization of one smt mutant revealed that suppression is due to a defect in a gene encoding a putative small ubiquitin-like modifier (SUMO) peptidase. Our results reveal a complex genetic network that lies downstream of MAT3/RB and implicate protein sumoylation as an important step for cell-cycle progression in cells that are missing MAT3/RB.

Investigating convergent actions of genes linked to familial Parkinson's disease.

BACKGROUND: Mutations in LRRK2 are among the most frequent genetic changes identified in Parkinson's disease (PD), but how LRRK2 contributes to the pathophysiology of PD is not known. OBJECTIVES: To investigate how expressing wild-type or G2019S LRRK2 modifies cellular responses to rotenone, a mitochondrial toxin. METHODS: We investigated the vulnerability to mitochondrial toxins in Caenorhabditis elegans expressing wild-type or G2019S LRRK2. RESULTS: We observed a powerful role for LRRK2 in mitochondrial biology. Overexpressing LRRK2 strongly protects C. elegans against rotenone toxicity. The G2019S LRRK2 construct also protected LRRK2 against rotenone, but to a lesser degree than wild-type LRRK2. Knockdown of lrk-1 potentiated rotenone toxicity. CONCLUSIONS: These data suggest that LRRK1/2 regulate mitochondrial physiology.

The search for genes related to a low-level response to alcohol determined by alcohol challenges.

BACKGROUND: A low level of response (LR) to alcohol seems to relate to a substantial proportion of the risk for alcoholism and to have significant heritability. METHODS: This report describes the results of a genome-wide segregation analysis for the first 139 pairs of full siblings by using an alcohol challenge protocol as a direct measure of LR. Subjects from 18 to 29 years old were selected if the original screen indicated they had an alcohol-dependent parent, reported a personal history of drinking but had no evidence of alcohol dependence, and had a full sibling with similar characteristics. Body sway and Subjective High Assessment Scale scores were measured at baseline and at regular intervals after the administration of a measured dose of alcohol. Participants and available parents were genotyped for 811 microsatellite markers, and resulting data were analyzed with a variance component method. RESULTS: Nine chromosome regions with logarithm of the odds ratio (LOD) between 2.2 and 3.2 were identified; several had previously been implicated regarding phenotypes relevant to alcoholism and the LR to alcohol. Several regions identified in the previous linkage study by using a retrospective self-report questionnaire were potentially confirmed by this study. The strongest evidence was on chromosomes 10, 11, and 22. CONCLUSIONS: Several chromosomal areas seem to relate to the low LR to alcohol as a risk factor for alcohol dependence.

Influence of the serotonin transporter gene-linked polymorphic region on the antidepressant response to fluvoxamine in Japanese depressed patients.

The presence of the long (l) variant of the serotonin (5-hydroxytryptamine: 5-HT) transporter gene-linked polymorphic region (5-HTTLPR) is reported to be associated with a more favorable and faster antidepressant effect of selective serotonin reuptake inhibitors in Caucasians. The frequency of the l allele is lower in Japanese than in Caucasians; therefore, the antidepressant effect of fluvoxamine can be not as good in Japanese as in Caucasians. The authors investigated whether 5-HTTLPR was associated with the antidepressant response to fluvoxamine in 66 Japanese patients with major depressive disorder in a protocolized-dosing 6-week study. The short (s) allele frequency was significantly higher in the responsive individuals than in the nonresponsive ones (P = .010). The present study suggests that fluvoxamine is not less effective in depressive patients carrying the s allele than in the ones carrying the l allele and it is not less effective in Japanese than in Caucasians.