Search tips
Search criteria

Results 1-9 (9)

Clipboard (0)

Select a Filter Below

Year of Publication
author:("Liu, wengler")
1.  Genomewide Association for Schizophrenia in the CATIE Study: Results of Stage 1 
Molecular psychiatry  2008;13(6):570-584.
Little is known for certain about the genetics of schizophrenia. The advent of genomewide association has been widely anticipated as holding promise as a means to identify reproducible DNA sequence variation associated with this important and debilitating disorder.
738 cases with DSM-IV schizophrenia (all participants in the CATIE study) and 733 group-matched controls were genotyped for 492,900 single nucleotide polymorphisms (SNPs) using the Affymetrix 500K two chip genotyping platform plus a custom 164K fill-in chip. Following multiple quality control steps for both subjects and SNPs, logistic regression analyses were used to assess the evidence for association of all SNPs with schizophrenia.
We identified a number of promising SNPs for follow-up studies, although no SNP or multi-marker combination of SNPs achieved genomewide statistical significance. Although a few signals coincided with genomic regions previously implicated in schizophrenia, chance could not be excluded.
These data do not provide evidence for the involvement of any genomic region with schizophrenia detectable with moderate sample size. However, planned GWAS for response phenotypes and inclusion of individual phenotype and genotype data from this study in meta-analyses holds promise for the eventual identification of susceptibility and protective variants.
PMCID: PMC3910086  PMID: 18347602
schizophrenia; genome-wide association; CATIE
2.  Temporal changes in gene expression in the skin of patients treated with isotretinoin provide insight into its mechanism of action 
Dermato-endocrinology  2009;1(3):177-187.
Isotretinoin (13-cis RA) is the most potent agent in the treatment of acne. Insights into its mechanism of action can lead to drug discovery of alternative compounds with comparable efficacy but improved safety. The goal of this study is to compare the temporal changes in gene expression in the skin of acne patients after 1 week and 8 weeks of treatment with isotretinoin. Microarray analysis was performed on skin biopsies taken from eight acne patients prior to and at 8 weeks of treatment with isotretinoin. Results were compared with data obtained from seven acne patients biopsied at one week of treatment in a prior study. Distinctly different patterns of gene expression were noted. At 8 weeks, genes encoding extracellular matrix proteins were upregulated and numerous genes encoding lipid metabolizing enzymes were downregulated. At 1 week, genes encoding differentiation markers, tumor suppressors and serine proteases were upregulated. Only three genes were commonly downregulated. The temporal changes in gene expression in patient skin noted with isotretinoin substantiate many previously reported effects of isotretinoin and other retinoids, suggesting a model wherein isotretinoin induces apoptosis leading to reduced sebaceous gland size, decreased expression of lipid metabolizing enzymes and increased matrix remodeling during acne resolution.
PMCID: PMC2835911  PMID: 20436886
13-cis retinoic acid; sebaceous gland; acne
3.  Early gene changes induced by isotretinoin in the skin provide clues to its mechanism of action 
Dermato-endocrinology  2009;1(2):100-101.
PMCID: PMC2835899  PMID: 20224692
13-cis retinoic acid; sebaceous gland; apoptosis; acne
4.  Neutrophil gelatinase–associated lipocalin mediates 13-cis retinoic acid–induced apoptosis of human sebaceous gland cells  
The Journal of Clinical Investigation  2008;118(4):1468-1478.
13-cis retinoic acid (13-cis RA; also known as isotretinoin) is the most potent agent available for treatment of acne. It is known that the drug induces apoptosis in cells cultured from human sebaceous glands, but its mechanism of action has not been determined. In this study, skin biopsies were taken from 7 patients with acne prior to and at 1 week of treatment with 13-cis RA. TUNEL staining confirmed that 13-cis RA induced apoptosis in sebaceous glands. Transcriptional profiling of patient skin and cultured human sebaceous gland cells (SEB-1 sebocytes) indicated that lipocalin 2 was among the genes most highly upregulated by 13-cis RA. Lipocalin 2 encodes neutrophil gelatinase–associated lipocalin (NGAL), which functions in innate immune defense and induces apoptosis of murine B lymphocytes. Increased immunolocalization of NGAL was noted in patients’ sebaceous glands following treatment with 13-cis RA, and recombinant NGAL induced apoptosis in SEB-1 sebocytes. Furthermore, apoptosis in response to 13-cis RA was inhibited in the presence of siRNA to lipocalin 2. These data indicate that NGAL mediates the apoptotic effect of 13-cis RA and suggest that agents that selectively induce NGAL expression in sebaceous glands might represent therapeutic alternatives to the use of 13-cis RA to treat individuals with acne.
PMCID: PMC2262030  PMID: 18317594
5.  β-Adrenergic Receptor Polymorphisms and Response to Salmeterol 
Rationale: Several studies suggest that patients with asthma who are homozygous for arginine at the 16th position of the β2-adrenergic receptor may not benefit from short-acting β-agonists.
Objectives: We investigated whether such genotype-specific effects occur when patients are treated with long-acting β-agonists and whether such effects are modified by concurrent inhaled corticosteroid (ICS) use.
Methods: We compared salmeterol response in patients with asthma homozygous for arginine at B16 (B16Arg/Arg) with those homozygous for glycine at B16 (B16Gly/Gly) in two separate cohorts. In the first, subjects were randomized to regular therapy with salmeterol while simultaneously discontinuing ICS therapy. In the second, subjects were randomized to regular therapy with salmeterol while continuing concomitant ICS.
Results: In both trials, B16Arg/Arg subjects did not benefit compared with B16Gly/Gly subjects after salmeterol was initiated. In the first cohort, compared with placebo, the addition of salmeterol was associated with a 51.4 L/min lower A.M. peak expiratory flow (PEF; p = 0.005) in B16Arg/Arg subjects(salmeterol, n = 12; placebo, n = 5) as compared with B16Gly/Gly subjects (salmeterol, n = 13; placebo, n = 13). In the second cohort, B16Arg/Arg subjects treated with salmeterol and ICS concurrently (n = 8) had a lower A.M. PEF (36.8 L/min difference, p = 0.048) than B16Gly/Gly subjects (n = 22) treated with the same regimen. In addition, B16 Arg/Arg subjects in the second cohort had lower FEV1 (0.42 L, p = 0.003), increased symptom scores (0.2 units, p = 0.034), and increased albuterol rescue use (0.95 puffs/d, p = 0.004) compared with B16Gly/Gly subjects.
Conclusions: Relative to B16Gly/Gly patients with asthma, B16Arg/Arg patients with asthma may have an impaired therapeutic response to salmeterol in either the absence or presence of concurrent ICS use. Investigation of alternate treatment strategies may benefit this group.
PMCID: PMC2662935  PMID: 16322642
asthma; β-adrenergic receptor; β-agonists; pharmacogenetics; salmeterol
6.  Genotypic probabilities for pairs of inbred relatives 
Expressions for the joint genotypic probabilities of two related individuals are used in many population and quantitative genetic analyses. These expressions, resting on a set of 15 probabilities of patterns of identity by descent among the four alleles at a locus carried by the relatives, are generally well known. There has been recent interest in special cases where the two individuals are both related and inbred, although there have been differences among published results. Here, we return to the original 15-probability treatment and show appropriate reductions for relatives when they are drawn from a population that itself is inbred or when the relatives have parents who are related. These results have application in affected-relative tests for linkage, and in methods for interpreting forensic genetic profiles.
PMCID: PMC1855075  PMID: 16048781
inbreeding; relatedness; affected-relative tests; forensic match probabilities
7.  Comparison of type I error for multiple test corrections in large single-nucleotide polymorphism studies using principal components versus haplotype blocking algorithms 
BMC Genetics  2005;6(Suppl 1):S78.
Although permutation testing has been the gold standard for assessing significance levels in studies using multiple markers, it is time-consuming. A Bonferroni correction to the nominal p-value that uses the underlying pair-wise linkage disequilibrium (LD) structure among the markers to determine the number of effectively independent tests has recently been proposed. We propose using the number of independent LD blocks plus the number of independent single-nucleotide polymorphisms for correction. Using the Collaborative Study on the Genetics of Alcoholism LD data for chromosome 21, we simulated 1,000 replicates of parent-child trio data under the null hypothesis with two levels of LD: moderate and high. Assuming haplotype blocks were independent, we calculated the number of independent statistical tests using 3 haplotype blocking algorithms. We then compared the type I error rates using a principal components-based method, the three blocking methods, a traditional Bonferroni correction, and the unadjusted p-values obtained from FBAT. Under high LD conditions, the PC method and one of the blocking methods were slightly conservative, whereas the 2 other blocking methods exceeded the target type I error rate. Under conditions of moderate LD, we show that the blocking algorithm corrections are closest to the desired type I error, although still slightly conservative, with the principal components-based method being almost as conservative as the traditional Bonferroni correction.
PMCID: PMC1866703  PMID: 16451692
8.  The impact of population heterogeneity on risk estimation in genetic counseling 
BMC Medical Genetics  2004;5:18.
Genetic counseling has been an important tool for evaluating and communicating disease susceptibility for decades, and it has been applied to predict risks for a wide class of hereditary disorders. Most diseases are complex in nature and are affected by multiple genes and environmental conditions; it is highly likely that DNA tests alone do not define all the genetic factors responsible for a disease, so that persons classified into the same risk group by DNA testing actually could have different disease susceptibilities. Ignorance of population heterogeneity may lead to biased risk estimates, whereas additional information on population heterogeneity may improve the precision of such estimates.
Although DNA tests are widely used, few studies have investigated the accuracy of the predicted risks. We examined the impact of population heterogeneity on predicted disease risks by simulation of three different heterogeneity scenarios and studied the precision and accuracy of the risks estimated from a logistic regression model that ignored population heterogeneity. Moreover, we also incorporated information about population heterogeneity into our original model and investigated the resulting improvement in the accuracy of risk estimation.
We found that heterogeneity in one or more categories could lead to biased estimates not only in the "contaminated" categories but also in other homogeneous categories. Incorporating information about population heterogeneity into the original model greatly improved the accuracy of risk estimation.
Our findings imply that without thorough knowledge about genetic basis of the disease, risks estimated from DNA tests may be misleading. Caution should be taken when evaluating the predicted risks obtained from genetic counseling. On the other hand, the improved accuracy of risk estimates after incorporating population heterogeneity information into the model did point out a promising direction for genetic counseling, since more and more new techniques are being invented and disease etiology is being better understood.
PMCID: PMC449710  PMID: 15228628
9.  Study of human SP-A, SP-B and SP-D loci: allele frequencies, linkage disequilibrium and heterozygosity in different races and ethnic groups 
BMC Genetics  2003;4:13.
SP-A, SP-B, and SP-D are pulmonary surfactant proteins. Several linkage and association studies have been done using these genes as markers to locate pulmonary disease susceptibility genes, but few have studied the markers systematically in different ethnic groups. Here we studied eight markers in SP-A, SP-B, and SP-D genes in seven ethnic groups from three races (Caucasian, Black and Hispanic). We measured the similarity of the marker distribution among the ethnic groups in order to see whether people in different ethnic groups or races could be mixed together for linkage and association studies. To evaluate the usefulness of these markers, we estimated the informativeness of each marker loci in the seven ethnic groups by assessing their heterozygosity and PIC values. We also conducted linkage disequilibrium (LD) analysis to identify associated marker loci and to estimate the haplotype frequencies in each of the seven ethnic groups in an attempt to find valuable haplotypes so that the level of polymorphism of the "markers" could be increased.
Our findings indicate that allele and genotype frequencies may be different between different ethnic groups, especially between ethnic groups from different races. The markers are in general polymorphic in a variety of study groups, especially for the two SP-A1 and SP-A2 markers. Two-locus LD analysis reveals that three pairs of loci are strongly associated together: B-18(A/C) with B1013(A/C), DA11(C/T) with DA160(A/G), SP-A1 with SP-A2. Three-locus LD analysis suggests that B-18(A/C), B1013(A/C) and B1580(C/T) are strongly associated with each other.
Allele and genotype frequency differences imply that different ethnic groups should be mixed with extreme caution before performing linkage and association studies. The associated markers could be used together to increase the level of polymorphism and the informativeness of the "markers".
PMCID: PMC194203  PMID: 12908879

Results 1-9 (9)