Biomedical subjects

Beth Bennett

Publications and source records attributed to Beth Bennett.

15 recordsLinked to original sources

PubMed2006

Confirmation and fine mapping of ethanol sensitivity quantitative trait loci, and candidate gene testing in the LXS recombinant inbred mice.

In previous studies, we have mapped quantitative trait loci (QTLs) for hypnotic sensitivity to ethanol using a small recombinant inbred (RI) panel and a large F(2) backcross. Alcohol sensitivity is a major predictor of long-term risk for alcoholism. We remapped hypnotic sensitivity using a new set of 75 RI strains, the LXS, derived from Inbred Long Sleep and Inbred Short Sleep strains. We expected to improve mapping resolution in the QTL regions and to identify novel QTLs for loss of the righting reflex due to ethanol. We used three common mapping algorithms (R/qtl, QTL Cartographer, and WebQTL) to map QTLs in the LXS, and we compared the results. Most mapping studies use only a single algorithm, an approach that may result in failure to identify minor QTLs. We confirmed most of our previously reported QTLs, although one major QTL from earlier work (Lore2) failed to replicate, possibly because it represented multiple linked genes separated by recombination in the RI strains. We also report narrowed confidence intervals, based on mapping with a new genetic resource of more than 4000 polymorphic single-nucleotide polymorphism markers. These narrowed confidence intervals will facilitate candidate gene identification and assessment of overlap with human regions specifying risk for alcoholism. Finally, we present an approach for using these RI strains to assess evidence for candidate genes in the narrowed intervals, and we apply this method to a strong candidate, the serotonin transporter.

Alcoholism↗

PubMed2006

Mouse genetic models in alcohol research.

Animal models offer several advantages for the study of complex human disorders such as alcoholism. No animal model replicates all aspects of alcoholism but different components of the disorder can be investigated using various rodent models. In this article, we review a select subset of the most widely used mouse genetic models in alcohol research. Different genetically defined strains and stocks of mice are useful for genetic, physiologic, behavioral and pharmacological studies of this devastating disorder. In the past decade, numerous genomic regions associated with a tendency for various behavioral components of alcoholism have been identified; recent applications of new methods are shedding light on quantitative trait genes. Many of the underlying genes should be identified in the near future.

Alcoholism↗

PubMed2006

Expression profiling identifies novel candidate genes for ethanol sensitivity QTLs.

The Inbred Long Sleep (ILS) and Inbred Short Sleep (ISS) mouse strains have a 16-fold difference in duration of loss of the righting response (LORR) following administration of a sedative dose of ethanol. Four quantitative trait loci (QTLs) have been mapped in these strains for this trait. Underlying each of these QTLs must be one or more genetic differences (polymorphisms in either gene coding or regulatory regions) influencing ethanol sensitivity. Because prior studies have tended to focus on differences in coding regions, genome-wide expression profiling in cerebellum was used here to identify candidate genes for regulatory region differences in these two strains. Fifteen differentially expressed genes were found that map to the QTL regions and polymorphisms were identified in the promoter regions of four of these genes by direct sequencing of ILS and ISS genomic DNA. Polymorphisms in the promoters of three of these genes, Slc22a4, Rassf2, and Tax1bp3, disrupt putative transcription factor binding sites. Slc22a4 and another candidate, Xrcc5, have human orthologs that map to genomic regions associated with human ethanol sensitivity in genetic linkage studies. These genes represent novel candidates for the LORR phenotype and provide new targets for future studies into the neuronal processes underlying ethanol sensitivity.

Animals↗

PubMed2006

QTL mapping for low-dose ethanol activation in the LXS recombinant inbred strains.

BACKGROUND: Most mouse quantitative trait loci (QTLs) for behavioral traits have been mapped using populations of mice derived from C57BL/6J (B6) and DBA/2J (D2). It is also important to identify QTLs for behavior in populations derived from other progenitors. We report results from QTL mapping for low-dose (ethanol) locomotor activation (LDA) using the recently developed LXS recombinant inbred (RI) strains, derived from Inbred Long Sleep (ILS) and Inbred Short Sleep (ISS) progenitors. The LXS RI panel has additional genetic variation, and greater power due to a larger number of strains, compared with other RI panels and strain crosses. METHODS: Mice were tested using a 3-day protocol in which activity levels were monitored for 15 minutes each day. On day 1, baseline activity was recorded; on day 2, mice were injected with saline before testing; and on day 3, mice were injected with 1.8 g/kg ethanol and tested. RESULTS: Several suggestive QTLs were found, on chromosomes 2, 3, 4, 7, 8, 12, and 13; 3 of these QTLs were sex-specific. CONCLUSIONS: Two apparently novel LDA QTLs were identified, on chromosomes 4 and 8. The other QTLs appear to replicate previously identified LDA QTLs. These replicated QTLs will be pursued in subsequent studies designed to identify candidate genes.

Animals↗

PubMed2005

Genetics of body weight in the LXS recombinant inbred mouse strains.

This is the first phenotypic analysis of 75 new recombinant inbred (RI) strains derived from ILS and ISS progenitors. We analyzed body weight in two independent cohorts of female mice at various ages and in males at 60 days. Body weight is a complex trait which has been mapped in numerous crosses in rodents. The LXS RI strains displayed a large range of weights, transgressing those of the inbred progenitors, supporting the utility of this large panel for mapping traits not selected in the progenitors. Numerous QTLs for body weight mapped in single- and multilocus scans. We assessed replication between these and previously reported QTLs based on overlapping confidence intervals of published QTLs for body weight at 60 days and used meta-analyses to determine combined p values for three QTL regions located on Chromosomes 4, 5, and 11. Strain distribution patterns of microsatellite marker genotypes, weight, and other phenotypes are available on WebQTL (http://www.webqtl.org/search.html ) and allow genetic mapping of any heritable quantitative phenotype measured in these strains. We report one such analysis, correlating brain and body weights. Large reference panels of RI strains, such as the LXS, are invaluable for identifying genetic correlations, GXE (Gene X Environment) interactions, and replicating previously identified QTLs.

Animals↗

PubMed2005

Norepinephrine transporter: a candidate gene for initial ethanol sensitivity in inbred long-sleep and short-sleep mice.

BACKGROUND: Altered noradrenergic neurotransmission is associated with depression and may contribute to drug abuse and alcoholism. Differential initial sensitivity to ethanol is an important predictor of risk for future alcoholism, making the inbred long-sleep (ILS) and inbred short-sleep (ISS) mice a useful model for identifying genes that may contribute to alcoholism. METHODS: In this study, molecular biological, neurochemical, and behavioral approaches were used to test the hypothesis that the norepinephrine transporter (NET) contributes to the differences in ethanol-induced loss of righting reflex (LORR) in ILS and ISS mice. RESULTS: We used these mice to investigate the NET as a candidate gene contributing to this phenotype. The ILS and ISS mice carry different DNA haplotypes for NET, showing eight silent differences between allelic coding regions. Only the ILS haplotype is found in other mouse strains thus far sequenced. Brain regional analyses revealed that ILS mice have 30 to 50% lower [3H]NE uptake, NET binding, and NET mRNA levels than ISS mice. Maximal [3H]NE uptake and NET number were reduced, with no change in affinity, in the ILS mice. These neurobiological changes were associated with significant influences on the behavioral phenotype of these mice, as demonstrated by (1) a differential response in the duration of ethanol-induced LORR in ILS and ISS mice pretreated with a NET inhibitor and (2) increased ethanol-induced LORR in LXS recombinant inbred (RI) strains, homozygous for ILS in the NET chromosomal region (44-47 cM), compared with ISS homozygous strains. CONCLUSIONS: This is the first report to suggest that the NET gene is one of many possible genetic factors influencing ethanol sensitivity in ILS, ISS, and LXS RI mouse strains.

Animals↗

PubMed2005

Open-label, dose escalation study of the safety and pharmacokinetic profile of tefibazumab in healthy volunteers.

Tefibazumab (Aurexis) is a humanized monoclonal antibody being evaluated as adjunctive therapy for the treatment of Staphylococcus aureus infections. This open-label, dose escalation study evaluated the safety and pharmacokinetics of tefibazumab in 19 healthy volunteers aged 18 to 69 years. Each subject received a single administration of tefibazumab at a dose of 2, 5, 10, or 20 mg/kg of body weight infused over 15 min. Plasma samples for pharmacokinetic assessments were obtained before infusion as well as 1, 6, 12, and 24 h and 3, 4, 7, 21, 28, 42, and 56 days after dosing. Plasma concentrations of tefibazumab were detected 1 h after the end of the infusion, with a mean maximum concentration of drug in serum (C(max)) of 59, 127, 252, and 492 microg/ml following doses of 2, 5, 10, and 20 mg/kg, respectively. The median time to maximum concentration of drug in serum (T(max)) was 1.0 h for each dose. The mean elimination half-life (t(1/2)) was approximately 22 days. The volume of distribution (V) was 4.7, 6.7, 7.2, and 7.2 liters after doses of 2, 5, 10, and 20 mg/kg, respectively. Clearance (CL) was 6.0, 9.2, 10.2, and 9.9 ml/hr, respectively. At the highest dose, plasma levels of tefibazumab were >100 microg/ml for 21 days. On day 56, the mean plasma concentrations were 6.3, 10.0, 16.4, and 30.5 microg/ml for the 2, 5, 10, and 20 mg/kg doses, respectively. Tefibazumab exhibited linear kinetics across doses of 5, 10, and 20 mg/kg. No anti-tefibazumab antibodies were detected after dosing in any subject. There were no serious adverse events, and tefibazumab was well tolerated over the entire dose range.

Adhesins, Bacterial↗

PubMed2004

Genetic structure of the LXS panel of recombinant inbred mouse strains: a powerful resource for complex trait analysis.

The set of LXS recombinant inbred (RI) strains is a new and exceptionally large mapping panel that is suitable for the analysis of complex traits with comparatively high power. This panel consists of 77 strains-more than twice the size of other RI sets--and will typically provide sufficient statistical power (beta = 0.8) to map quantitative trait loci (QTLs) that account for approximately 25% of genetic variance with a genomewide p < 0.05. To characterize the genetic architecture of this new set of RI strains, we genotyped 330 MIT microsatellite markers distributed on all autosomes and the X Chromosome and assembled error-checked meiotic recombination maps that have an average F2-adjusted marker spacing of approximately 4 cM. The LXS panel has a genetic structure consistent with random segregation and subsequent fixation of alleles, the expected 3-4 x map expansion, a low level of nonsyntenic association among loci, and complete independence among all 77 strains. Although the parental inbred strains-Inbred Long-Sleep (ILS) and Inbred Short-Sleep (ISS)--were derived originally by selection from an 8-way heterogeneous stock selected for differential sensitivity to sedative effects of ethanol, the LXS panel is also segregating for many other traits. Thus, the LXS panel provides a powerful new resource for mapping complex traits across many systems and disciplines and should prove to be of great utility in modeling the genetics of complex diseases in human populations.

Alleles↗

PubMed2004

The Collaborative Cross, a community resource for the genetic analysis of complex traits.

The goal of the Complex Trait Consortium is to promote the development of resources that can be used to understand, treat and ultimately prevent pervasive human diseases. Existing and proposed mouse resources that are optimized to study the actions of isolated genetic loci on a fixed background are less effective for studying intact polygenic networks and interactions among genes, environments, pathogens and other factors. The Collaborative Cross will provide a common reference panel specifically designed for the integrative analysis of complex systems and will change the way we approach human health and disease.

Animals↗

PubMed2004

Differential effects of ethanol on gamma-aminobutyric acid-A receptor-mediated synaptic currents in congenic strains of inbred long and short-sleep mice.

BACKGROUND: Ethanol enhances gamma-aminobutyric acid (GABA)A receptor-mediated responses in the brain, and this enhancement is greater in a mouse line behaviorally more sensitive to ethanol (long sleep) than in a line (short sleep) behaviorally less ethanol sensitive (assayed by loss of righting; sleep time). Quantitative trait locus (QTL) analysis of inbred long sleep (ILS) and inbred short sleep (ISS) phenotypes revealed four chromosomal regions (Lore1, Lore2, Lore4, and Lore5) that together account for approximately 50% of ethanol-induced sleep-time variance. Congenic strains were generated, each of which is homozygous for one of four ISS Lore QTLs on the ILS background. These congenic mouse strains are ideally suited for asking which QTL regions might correlate with other phenotypes that differ between ILS and ISS mice. Here we used the congenics to investigate altered GABAA responses to ethanol. METHODS: Evoked GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) were measured by whole-cell voltage-clamp recording procedures in CA1 pyramidal neurons in hippocampal brain slices. RESULTS: GABAA IPSC responses in hippocampal brain slices from ILS mice were significantly enhanced by 80 mM ethanol, whereas those from ISS mice were not affected. ILS.Lore2 and ILS.Lore5 congenic strains were significantly enhanced by 80 mM ethanol, similar to the background (control) ILS mice. However, ethanol had no significant effect on GABAA responses in ILS.Lore1 and ILS.Lore4 congenic mice, similar to the ISS mice, thus reflecting the influence of ISS alleles on the ILS phenotype. CONCLUSIONS: Our results suggest that alleles located in the Lore1 and Lore4 QTL regions confer ethanol sensitivity of GABAA receptor-mediated IPSCs. Thus, for these QTLs, GABAA IPSCs may represent an endophenotype of sedative/hypnotic sensitivity to ethanol. Although the Lore2 and Lore5 QTL regions have a significant effect on sleep time, they do not play a significant role in the differential ethanol enhancement of GABAA IPSCs between ILS and ISS mice.

Animals↗

PubMed2004

Confirmation and genetic dissection of a major quantitative trait locus for alcohol preference drinking.

OBJECTIVE: In previous work, we created congenic strains that carry the DBA/2IBG (D2) region for alcohol preference on chromosome 2, on an otherwise C57BL/6IBG (B6) background. Here, we report construction and testing of interval-specific congenic recombinant strains (ISCRSs) for the purpose of narrowing the quantitative trait loci (QTL) interval. METHODS: ISCRSs were derived by identifying mice that carry recombination events in the D2 interval, during the backcrossing for congenics. Recombinant mice were backcrossed to B6, and progeny that carry the reduced chromosome 2 region were tested for its effect on the alcohol preference phenotype. RESULTS: We developed multiple ISCR strains, which spanned the QTL interval. Three of these showed the D2 phenotype of reduced alcohol consumption. The overlap of two of these strains reduced the QTL interval from 66.8 to 3.5 Mb. A third positive ISCRS suggests the possibility of a second, linked QTL. CONCLUSIONS: Use of ISCRSs can narrow a QTL region to a few Mb. This reduced interval size will facilitate identification of candidate genes, through bioinformatics, gene expression, and DNA sequencing strategies. Potential difficulties, including reduced power as a result of variable phenotypes or small effect size, are discussed.

Alcohol Drinking↗

PubMed2003

The nature and identification of quantitative trait loci: a community's view.

This white paper by eighty members of the Complex Trait Consortium presents a community's view on the approaches and statistical analyses that are needed for the identification of genetic loci that determine quantitative traits. Quantitative trait loci (QTLs) can be identified in several ways, but is there a definitive test of whether a candidate locus actually corresponds to a specific QTL?

Animals↗

PubMed2002

Possible pleiotropic effects of genes specifying sedative/hypnotic sensitivity to ethanol on other alcohol-related traits.

BACKGROUND: Initial sensitivity to ethanol is a predictor of alcohol abuse that has been studied extensively in both human and animal populations. Selection for initial sensitivity to the sedative/hypnotic effects of ethanol resulted in the long-sleep and short-sleep lines of mice. Some of the genes selected in these lines could also specify differential responses in other ethanol-related phenotypes and, perhaps, for other drugs of abuse. We assessed congenic mice carrying a single quantitative trait locus (QTL) from the inbred long-sleep (ILS) or inbred short-sleep (ISS) strain on the reciprocal background for a number of ethanol- and pentobarbital-related phenotypes. METHODS: Each congenic strain was tested for ethanol elimination rates at 4.1 g/kg, ethanol-induced ataxia at 2.0 g/kg, ethanol-induced hypothermia at 4.1 g/kg, and pentobarbital-induced loss of righting reflex (LORR) at 60 mg/kg. Additionally, the ILS.ISS congenics were tested for low-dose ethanol-induced activation (LDA) at five doses ranging from 0.6 to 1.2 g/kg ethanol, and the ISS.ILS congenics were tested for LDA at 1.8 g/kg of ethanol. RESULTS: There was little difference in the ethanol elimination rate between congenics and background strains, although a modest sex effect was found, with the females eliminating ethanol more rapidly than the males. We were unable to replicate previous differences found in LDA for the congenic on the ISS background, because none of the congenics differed from controls for LDA. congenics showed a differential effect of pentobarbital-induced LORR in the expected directions. The congenics on the ISS background showed more ethanol-induced ataxia than the ISS controls. Additionally, the hypothermic response seems affected by and and maybe others. CONCLUSIONS: At least two regions carrying a QTL specifying sensitivity to high doses of ethanol cospecify altered sensitivity in other measures of alcohol action. Specifically, these QTLs clearly affect ethanol-induced hypothermia and pentobarbital-induced LORR and possibly ethanol-induced ataxia.

Alcoholism↗

PubMed2002

Fine mapping of polymorphic alcohol-related quantitative trait loci candidate genes using interval-specific congenic recombinant mice.

BACKGROUND: The inbred long-sleep (ILS) and inbred short-sleep (ISS) strains of mice are widely studied as a model of initial sensitivity to alcohol. Recently, a large comparative DNA sequencing study of candidate genes located within the four Lore quantitative trait loci (QTLs) associated with the ethanol-induced loss of righting reflex in ILS and ISS mice has identified eight genes that contain coding region differences corresponding to amino acid changes. Here, recently developed interval-specific congenic recombinant mice (ISCRs) have been used to map these genes in relationship to newly narrowed QTL regions. METHODS: Regions of candidate genes containing DNA differences corresponding to previously identified amino acid changes between ISS and ILS mice were amplified from either genomic DNA or complementary DNA from ISCR mice using polymerase chain reaction. The products were purified and directly sequenced to determine the genotypes for each polymorphism. On the basis of these genotypic data, each candidate gene was determined to be located either within or outside of recently narrowed Lore QTL intervals. RESULTS: Of these eight candidates with protein-coding differences, five are now excluded from their respective Lore intervals. The other three (Znf142, Ptprn, and Znf133) have been localized to the narrowed QTL intervals. CONCLUSIONS: These three central nervous system genes (Znf142, Ptprn, and Znf133) represent promising candidates for involvement in the differential sensitivity to alcohol exhibited between ILS and ISS mice. This study also demonstrates how the combination of high-throughput comparative gene sequencing and concomitant genetic fine mapping of QTL regions with ISCRs can be an effective tool for accelerating the process of moving from QTL to gene.

Alcoholism↗

PubMed2002

Genetic dissection of quantitative trait loci specifying sedative/hypnotic sensitivity to ethanol: mapping with interval-specific congenic recombinant lines.

BACKGROUND: Linkage studies alone do not produce sufficient resolution to narrow the location of a quantitative trait locus (QTL) to a small-enough chromosomal region for gene identification. One solution to this problem is to use interval-specific congenic recombinant (ISCR) lines to narrow the chromosomal interval known to contain the QTL. In previous work, we mapped four QTLs for differential ethanol sensitivity in the inbred long-sleep (ILS) and inbred short-sleep (ISS) strains and generated reciprocal congenic strains in which each full QTL interval from ILS was bred onto the ISS background and vice versa. METHODS: ISCR lines were derived by identifying mice carrying recombination events in the congenic interval during backcrossing of the ISS.ILS.Lore congenics to ISS. Recombinant mice were backcrossed to ISS, and progeny carrying the ISCR chromosome were identified and tested to determine whether the ISCR region carried the donor Lore QTL. RESULTS: We developed multiple ISCR lines for each Lore QTL, in which the QTL interval was broken into a number of smaller intervals. For all four QTLs, we reduced the size of the interval, in one case to 3.7 cM. CONCLUSIONS: Use of ISCR lines can narrow each Lore candidate region to a few centimorgans. Such an interval size is conducive to brute-force approaches to identify candidate genes, entailing bioinformatics, gene expression, and DNA sequencing strategies.

Alcohol Drinking↗