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1.  Handedness and the X chromosome: The role of androgen receptor CAG-repeat length 
Scientific Reports  2015;5:8325.
Prenatal androgen exposure has been suggested to be one of the factors influencing handedness, making the androgen receptor gene (AR) a likely candidate gene for individual differences in handedness. Here, we examined the relationship between the length of the CAG-repeat in AR and different handedness phenotypes in a sample of healthy adults of both sexes (n = 1057). Since AR is located on the X chromosome, statistical analyses in women heterozygous for CAG-repeat lengths are complicated by X chromosome inactivation. We thus analyzed a sample of women that were homozygous for the CAG-repeat length (n = 77). Mixed-handedness in men was significantly associated with longer CAG-repeat blocks and women homozygous for longer CAG-repeats showed a tendency for stronger left-handedness. These results suggest that handedness in both sexes is associated with the AR CAG-repeat length, with longer repeats being related to a higher incidence of non-right-handedness. Since longer CAG-repeat blocks have been linked to less efficient AR function, these results implicate that differences in AR signaling in the developing brain might be one of the factors that determine individual differences in brain lateralization.
doi:10.1038/srep08325
PMCID: PMC4321186  PMID: 25659367
2.  SOX9 Duplication Linked to Intersex in Deer 
PLoS ONE  2013;8(9):e73734.
A complex network of genes determines sex in mammals. Here, we studied a European roe deer with an intersex phenotype that was consistent with a XY genotype with incomplete male-determination. Whole genome sequencing and quantitative real-time PCR analyses revealed a triple dose of the SOX9 gene, allowing insights into a new genetic defect in a wild animal.
doi:10.1371/journal.pone.0073734
PMCID: PMC3765313  PMID: 24040047
3.  PCSK6 VNTR Polymorphism Is Associated with Degree of Handedness but Not Direction of Handedness 
PLoS ONE  2013;8(6):e67251.
Although the left and right human cerebral hemispheres differ both functionally and anatomically, the mechanisms that underlie the establishment of these hemispheric specializations, as well as their physiological and behavioral implications, remain largely unknown. Since cerebral asymmetry is strongly correlated with handedness, and handedness is assumed to be influenced by a number of genetic and environmental factors, we performed an association study of LRRTM1 rs6733871 and a number of polymorphisms in PCSK6 and different aspects of handedness assessed with the Edinburgh handedness inventory in a sample of unrelated healthy adults (n = 1113). An intronic 33bp variable-number tandem repeat (VNTR) polymorphism in PCSK6 (rs10523972) shows a significant association (significance threshold: p<0.0025, adjusted for multiple comparisons) with a handedness category comparison (P = 0.0005) and degree of handedness (P = 0.001). These results provide further evidence for the role of PCSK6 as candidate for involvement in the biological mechanisms that underlie the establishment of normal brain lateralization and thus handedness and support the assumption that the degree of handedness, instead the direction, may be the more appropriate indicator of cerebral organization.
doi:10.1371/journal.pone.0067251
PMCID: PMC3695088  PMID: 23826248
4.  Cholecystokinin A Receptor (CCKAR) Gene Variation Is Associated with Language Lateralization 
PLoS ONE  2013;8(1):e53643.
Schizophrenia is a psychiatric disorder associated with atypical handedness and language lateralization. However, the molecular mechanisms underlying these functional changes are still poorly understood. Therefore, the present study was aimed at investigating whether variation in schizophrenia-related genes modulates individual lateralization patterns. To this end, we genotyped 16 single nucleotide polymorphisms that have previously been linked to schizophrenia on a meta-analysis level in a sample of 444 genetically unrelated healthy participants and examined the association of these polymorphisms with handedness, footedness and language lateralization. We found a significant association of the cholecystokinin-A receptor (CCKAR) gene variation rs1800857 and language lateralization assessed using the dichotic listening task. Individuals carrying the schizophrenia risk allele C of this polymorphism showed a marked reduction of the typical left-hemispheric dominance for language processing. Since the cholecystokinin A receptor is involved in dopamine release in the central nervous system, these findings suggest that genetic variation in this receptor may modulate language lateralization due to its impact on dopaminergic pathways.
doi:10.1371/journal.pone.0053643
PMCID: PMC3544920  PMID: 23341962
6.  NMDA receptor gene variations as modifiers in Huntington disease: a replication study 
PLoS Currents  2011;3:RRN1247.
Several candidate modifier genes which, in addition to the pathogenic CAG repeat expansion, influence the age at onset (AO) in Huntington disease (HD) have already been described. The aim of this study was to replicate association of variations in the N-methyl D-aspartate receptor subtype genes GRIN2A and GRIN2B in the “REGISTRY” cohort from the European Huntington Disease Network (EHDN). The analyses did replicate the association reported between the GRIN2A rs2650427 variation and AO in the entire cohort. Yet, when subjects were stratified by AO subtypes, we found nominally significant evidence for an association of the GRIN2A rs1969060 variation and the GRIN2B rs1806201 variation. These findings further implicate the N-methyl D-aspartate receptor subtype genes as loci containing variation associated with AO in HD.
doi:10.1371/currents.RRN1247
PMCID: PMC3186947  PMID: 21989477
8.  PGC-1alpha downstream transcription factors NRF-1 and TFAM are genetic modifiers of Huntington disease 
Background
Huntington disease (HD) is an inherited neurodegenerative disease caused by an abnormal expansion of a CAG repeat in the huntingtin HTT (HD) gene. The primary genetic determinant of the age at onset (AO) is the length of the HTT CAG repeat; however, the remaining genetic contribution to the AO of HD has largely not been elucidated. Recent studies showed that impaired functioning of the peroxisome proliferator-activated receptor gamma coactivator 1a (PGC-1alpha) contributes to mitochondrial dysfunction and appears to play an important role in HD pathogenesis. Further genetic evidence for involvement of PGC-1alpha in HD pathogenesis was generated by the findings that sequence variations in the PPARGC1A gene encoding PGC-1alpha exert modifying effects on the AO in HD. In this study, we hypothesised that polymorphisms in PGC-1alpha downstream targets might also contribute to the variation in the AO.
Results
In over 400 German HD patients, polymorphisms in the nuclear respiratory factor 1 gene, NRF-1, and the mitochondrial transcription factor A, encoded by TFAM showed nominally significant association with AO of HD. When combining these results with the previously described modifiers rs7665116 in PPARGC1A and C7028T in the cytochrome c oxidase subunit I (CO1, mt haplogroup H) in a multivariable model, a substantial proportion of the variation in AO can be explained by the joint effect of significant modifiers and their interactions, respectively.
Conclusions
These results underscore that impairment of mitochondrial function plays a critical role in the pathogenesis of HD and that upstream transcriptional activators of PGC-1alpha may be useful targets in the treatment of HD.
doi:10.1186/1750-1326-6-32
PMCID: PMC3117738  PMID: 21595933
9.  Evidence for STAT4 as a Common Autoimmune Gene: rs7574865 Is Associated with Colonic Crohn's Disease and Early Disease Onset 
PLoS ONE  2010;5(4):e10373.
Background
Recent studies demonstrated an association of STAT4 variants with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), indicating that multiple autoimmune diseases share common susceptibility genes. We therefore investigated the influence of STAT4 variants on the susceptibility and phenotype of inflammatory bowel diseases (IBD) in a large patient and control cohort.
Methodology/Principal Findings
Genomic DNA from 2704 individuals of Caucasian origin including 857 patients with Crohn's disease (CD), 464 patients with ulcerative colitis (UC), and 1383 healthy, unrelated controls was analyzed for seven SNPs in the STAT4 gene (rs11889341, rs7574865, rs7568275, rs8179673, rs10181656, rs7582694, rs10174238). In addition, a detailed genotype-phenotype analysis was performed. Our analysis revealed an association of the STAT4 SNP rs7574865 with overall decreased susceptibility to CD (p = 0.047, OR 0.86 [95% CI 0.74–0.99]). However, compared to CD patients carrying the wild type genotype, the STAT4 SNP rs7574865 was significantly associated with early CD onset (p = 0.021) and colonic CD (p = 0.008; OR = 4.60, 95% CI 1.63–12.96). For two other STAT4 variants, there was a trend towards protection against CD susceptibility (rs7568275, p = 0.058, OR 0.86 [95% CI 0.74–1.00]; rs10174238, p = 0.057, OR 0.86 [95% CI 0.75–1.00]). In contrast, we did not observe any association with UC susceptibility. Evidence for weak gene-gene interaction of STAT4 with the IL23R SNP rs11209026 was lost after Bonferroni correction.
Conclusions/Significance
Our results identified the STAT4 SNP rs7574865 as a disease-modifying gene variant in colonic CD. However, in contrast to SLE and RA, the effect of rs7574865 on CD susceptibility is only weak.
doi:10.1371/journal.pone.0010373
PMCID: PMC2861592  PMID: 20454450
10.  Genetic Variability of RXRB, PPARA, and PPARG in Wegener's Granulomatosis 
PPAR Research  2009;2009:786781.
A major genomic region involved in Wegener's granulomatosis includes the gene for retinoid receptor beta (RXRB) which forms heterodimers with peroxisome proliferator-activated receptors (PPARs). It is unclear whether this association directly arises from the RXRB allele(s) or via a linked variation. In order to reveal any hitherto unknown and potentially disease-relevant variation of the RXRB gene, we have genotyped four tagging SNPs of this genomic region and have directly sequenced selected WG patients and controls representing disease-associated haplotypes. Additionally, we have genotyped 2 SNPs each in the genes for PPARα and PPARγ (PPARA and PPARG). Hence, we confirmed the strong association of the RXRB locus with WG but could not reveal any novel variation in RXRB. None of the PPARA and PPARG SNPs showed association with WG. Moreover, no epistatic effect was seen between RXRB and PPARA/PPARG alleles. These results do not support an etiopathological role of PPAR in WG. Analyses of further genes functionally linked to RXRB may provide additional data useful to evaluate the RXRB association found in WG.
doi:10.1155/2009/786781
PMCID: PMC2639638  PMID: 19223982
11.  The CYP2J2 G-50T polymorphism and myocardial infarction in patients with cardiovascular risk profile 
Background
Cytochrome P450 (CYP) enzyme 2J2, an epoxygenase predominantly expressed in the heart, metabolises arachidonic acid to biologically active eicosanoids. One of the CYP2J2 products, 11, 12-epoxyeicosatrienoic acid, has several vasoprotective effects. The CYP2J2-G-50T-promotor polymorphism decreases gene expression and is associated with coronary artery disease. This association supports the vascular protective role of CYP-derived eicosanoids in cardiovascular disease. In the present study, we investigated the influence of this polymorphism on survived myocardial infarction in two study groups of patients with on average high cardiovascular risk profile.
Methods
The CYP2J2 polymorphism was genotyped in two groups of patients that were collected with the same method of clinical data collection. Data from 512 patients with sleep apnoea (group: OSA) and on average high cardiovascular risk profile and from another 488 patients who were admitted for coronary angiography (CAR-group) were evaluated for a potential correlation of the CYP2J2 polymorphism G-50T and a history of myocardial infarction. The G-50T polymorphism of the CYP2J2 gene was genotyped by allele specific restriction and light cycler analysis.
Results
The T-allele of the polymorphism was found in 111 (11.1%; CAR-group: N = 65, 13.3%; OSA: N = 46, 9.0%). 146 patients had a history of myocardial infarction (CAR: N = 120, 24.6%; OSA: N = 26, 5.1%). Cardiovascular risk factors were equally distributed between the different genotypes of the CYP2J2 G-50T polymorphism. In the total group of 1000 individuals, carriers of the T-allele had significantly more myocardial infarctions compared to carriers of the wild type (T/T or G/T: 21.6%; G/G: 13.7%; p = 0.026, odds ratio 1.73, 95%-CI [1.06–2.83]). In the multivariate logistic regression analysis the odds ratio for a history of myocardial infarction in carriers of the T-allele was 1.611, 95%-CI [0.957–2.731] but this trend was not significant (p = 0.073).
Conclusion
In presence of other risk factors, the CYP2J2 G-50T failed to show a significant role in the development of myocardial infarction. However, since our result is close to the border of significance, this question should be clarified in larger, prospective studies in the future.
doi:10.1186/1471-2261-8-41
PMCID: PMC2626571  PMID: 19105833
12.  Genomic NGFB variation and multiple sclerosis in a case control study 
BMC Medical Genetics  2008;9:107.
Background
Nerve growth factor β (NGFB) is involved in cell proliferation and survival, and it is a mediator of the immune response. ProNGF, the precursor protein of NGFB, has been shown to induce cell death via interaction with the p75 neurotrophin receptor. In addition, this neurotrophin is differentially expressed in males and females. Hence NGFB is a good candidate to influence the course of multiple sclerosis (MS), much like in the murine model of experimental autoimmune encephalomyelitis (EAE).
Methods
Ten single nucleotide polymorphisms (SNPs) were genotyped in the NGFB gene in up to 1120 unrelated MS patients and 869 controls. Expression analyses were performed for selected MS patients in order to elucidate the possible functional relevance of the SNPs.
Results
Significant association of NGFB variations with MS is evident for two SNPs. NGFB mRNA seems to be expressed in sex- and disease progression-related manner in peripheral blood mononuclear cells.
Conclusion
NGFB variation and expression levels appear as modulating factors in the development of MS.
doi:10.1186/1471-2350-9-107
PMCID: PMC2613874  PMID: 19063739
13.  Variation in genes encoding eosinophil granule proteins in atopic dermatitis patients from Germany 
Background
Atopic dermatitis (AD) is believed to result from complex interactions between genetic and environmental factors. A main feature of AD as well as other allergic disorders is serum and tissue eosinophilia. Human eosinophils contain high amounts of cationic granule proteins, including eosinophil cationic protein (ECP), eosinophil-derived neurotoxin (EDN), eosinophil peroxidase (EPO) and major basic protein (MBP). Recently, variation in genes encoding eosinophil granule proteins has been suggested to play a role in the pathogenesis of allergic disorders. We therefore genotyped selected single nucleotide polymorphisms within the ECP, EDN, EPO and MBP genes in a cohort of 361 German AD patients and 325 healthy controls.
Results
Genotype and allele frequencies did not differ between patients and controls for all polymorphisms investigated in this study. Haplotype analysis did not reveal any additional information.
Conclusion
We did not find evidence to support an influence of variation in genes encoding eosinophil granule proteins for AD pathogenesis in this German cohort.
doi:10.1186/1477-5751-7-9
PMCID: PMC2596079  PMID: 19014520
14.  rs1004819 Is the Main Disease-Associated IL23R Variant in German Crohn's Disease Patients: Combined Analysis of IL23R, CARD15, and OCTN1/2 Variants 
PLoS ONE  2007;2(9):e819.
Background
The IL23R gene has been identified as a susceptibility gene for inflammatory bowel disease (IBD) in the North American population. The aim of our study was to test this association in a large German IBD cohort and to elucidate potential interactions with other IBD genes as well as phenotypic consequences of IL23R variants.
Methods
Genomic DNA from 2670 Caucasian individuals including 833 patients with Crohn's disease (CD), 456 patients with ulcerative colitis (UC), and 1381 healthy unrelated controls was analyzed for 10 IL23R SNPs. Genotyping included the NOD2 variants p.Arg702Trp, p.Gly908Arg, and p.Leu1007fsX1008 and polymorphisms in SLC22A4/OCTN1 (1672 C→T) and SLC22A5/OCTN2 (–207 G→C).
Results
All IL23R gene variants analyzed displayed highly significant associations with CD. The strongest association was found for the SNP rs1004819 [P = 1.92×10−11; OR 1.56; 95 % CI (1.37–1.78)]. 93.2% of the rs1004819 TT homozygous carriers as compared to 78% of CC wildtype carriers had ileal involvement [P = 0.004; OR 4.24; CI (1.46–12.34)]. The coding SNP rs11209026 (p.Arg381Gln) was protective for CD [P = 8.04×10−8; OR 0.43; CI (0.31–0.59)]. Similar, but weaker associations were found in UC. There was no evidence for epistasis between the IL23R gene and the CD susceptibility genes CARD15 and SLC22A4/5.
Conclusion
IL23R is an IBD susceptibility gene, but has no epistatic interaction with CARD15 and SLC22A4/5. rs1004819 is the major IL23R variant associated with CD in the German population, while the p.Arg381Gln IL23R variant is a protective marker for CD and UC.
doi:10.1371/journal.pone.0000819
PMCID: PMC1950565  PMID: 17786191
15.  Risk factors and myocardial infarction in patients with obstructive sleep apnea: impact of β2-adrenergic receptor polymorphisms 
BMC Medicine  2007;5:1.
Background
The increased sympathetic nervous activity in patients with obstructive sleep apnea (OSA) is largely responsible for the high prevalence of arterial hypertension, and it is suggested to adversely affect triglyceride and high-density lipoprotein (HDL) cholesterol levels in these patients. The functionally relevant polymorphisms of the β2-adrenergic receptor (Arg-47Cys/Arg16Gly and Gln27Glu) have been shown to exert modifying effects on these risk factors in previous studies, but results are inconsistent.
Methods
We investigated a group of 429 patients (55 ± 10.7 years; 361 men, 68 women) with moderate to severe obstructive sleep apnea (apnea/hypopnea index (AHI) 29.1 ± 23.1/h) and, on average, a high cardiovascular risk profile (body mass index 31.1 ± 5.6, with hypertension in 60.1%, dyslipidemia in 49.2%, and diabetes in 17.2% of patients). We typed the β2-adrenergic receptor polymorphisms and investigated the five most frequent haplotypes for their modifying effects on OSA-induced changes in blood pressure, heart rate, and lipid levels. The prevalence of cardiovascular risk factors and coronary heart disease (n = 55, 12.8%) and survived myocardial infarction (n = 27, 6.3%) were compared between the genotypes and haplotypes.
Results
Multivariate linear/logistic regressions revealed a significant and independent (from BMI, age, sex, presence of diabetes, use of antidiabetic, lipid-lowering, and antihypertensive medication) influence of AHI on daytime systolic and diastolic blood pressure, heart rate, prevalence of hypertension, and triglyceride and HDL levels. The β2-adrenergic receptor genotypes and haplotypes showed no modifying effects on these relationships or on the prevalence of dyslipidemia, diabetes, and coronary heart disease, yet, for all three polymorphisms, heterozygous carriers had a significantly lower relative risk for myocardial infarction (Arg-47Cys: n = 195, odds ratio (OR) = 0.32, P = 0.012; Arg16Gly: n = 197, OR = 0.39, P = 0.031; Gln27Glu: OR = 0.37, P = 0.023). Carriers of the most frequent haplotype (n = 113) (haplotype 1; heterozygous for all three polymorphisms) showed a five-fold lower prevalence of survived myocardial infarction (OR = 0.21, P = 0.023).
Conclusion
Our study showed no significant modifying effect of the functionally relevant β2-adrenergic receptor polymorphisms on OSA-induced blood pressure, heart rate, or lipid changes. Nevertheless, heterozygosity of these polymorphisms is associated with a lower prevalence of survived myocardial infarction in this group with, on average, a high cardiovascular risk profile.
doi:10.1186/1741-7015-5-1
PMCID: PMC1785383  PMID: 17198546
16.  Haplotype-defined linkage region for gPRA in Schapendoes dogs 
Molecular Vision  2007;13:174-180.
Purpose
In order to determine the molecular basis of canine generalized progressive retinal atrophy (gPRA), we initiated whole-genome scanning for linkage in gPRA-informative pedigrees of the Schapendoes breed.
Methods
Detailed pedigree and ophthalmological data were assembled in selected Schapendoes pedigrees. A whole-genome scan was initiated by two-point linkage analysis using microsatellite markers in combination with haplotype analyses. Mutation screening was carried out in respective candidate genes by DNA sequencing of amplified products and quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR).
Results
Genotyping data of the microsatellite genome scan evidenced a peak two-point lod score of 4.78 for marker REN93E07 on CFA20. Haplotype analyses inferred the gPRA locus in a 5.6 megabase (Mb) region between markers FH3358 and TL336MS. Mutation screening in the genes CACNA2D3, HT017, and WNT5A revealed no causative sequence deviations. In addition, CACNA2D3 mRNA levels were equivalent in retinas of affected and healthy dogs.
Conclusions
By genome-wide linkage analysis a region for gPRA was identified and fine-localized in Schapendoes dogs. Although the mutation causing gPRA in Schapendoes dogs has not yet been identified, we established indirect DNA testing for gPRA in this breed based on linkage analysis data.
PMCID: PMC2533032  PMID: 17327822
17.  No association between polymorphisms in the BDNF gene and age at onset in Huntington disease 
BMC Medical Genetics  2006;7:79.
Background
Recent evidence suggests that brain-derived neurotrophic factor (BDNF) is an attractive candidate for modifying age at onset (AO) in Huntington disease (HD). In particular, the functional Val66Met polymorphism appeared to exert a significant effect. Here we evaluate BDNF variability with respect to AO of HD using markers that represent the entire locus.
Methods
Five selected tagging polymorphisms were genotyped across a 65 kb region comprising the BDNF gene in a well established cohort of 250 unrelated German HD patients.
Results
Addition of BDNF genotype variations or one of the marker haplotypes to the effect of CAG repeat lengths did not affect the variance of the AO.
Conclusion
We were unable to verify a recently reported association between the functional Val66Met polymorphism in the BDNF gene and AO in HD. From our findings, we conclude that neither sequence variations in nor near the gene contribute significantly to the variance of AO.
doi:10.1186/1471-2350-7-79
PMCID: PMC1637098  PMID: 17096834
18.  Charcot-Marie-Tooth neuropathy type 2A: novel mutations in the mitofusin 2 gene (MFN2) 
BMC Medical Genetics  2006;7:53.
Background
Charcot-Marie-Tooth neuropathies are a group of genetically heterogeneous diseases of the peripheral nervous system. Mutations in the MFN2 gene have been reported as the primary cause of Charcot-Marie-Tooth disease type 2A.
Methods
Patients with the clinical diagnosis of Charcot-Marie-Tooth type 2 were screened using single strand conformation polymorphism (SSCP). All DNA samples showing band shifts in the SSCP analysis were amplified from genomic DNA and cycle sequenced.
Results
We analyzed a total of 73 unrelated patients with a clinical diagnosis of CMT 2. Overall, novel mutations were detected in 6 patients. c.380G>T (G127V), c.1128G>A (M376I), c.1040A>T (E347V), c.1403G>A (R468H), c.2113G>A (V705I), and c.2258_2259insT (L753fs).
Conclusion
We confirmed a significant role of mutations in MFN2 in the pathogenesis of Charcot-Marie-Tooth disease type 2.
doi:10.1186/1471-2350-7-53
PMCID: PMC1524942  PMID: 16762064
19.  Failure to confirm influence of Methyltetrahydrofolate reductase (MTHFR) polymorphisms on age at onset of Huntington disease 
Background
Huntington disease (HD) is a fully penetrant, autosomal dominantly inherited disorder associated with abnormal expansions of a stretch of perfect CAG repeats in the 5' part of the IT15 gene. The number of repeat units is highly predictive for the age at onset (AO) of the disorder. But AO is only modestly correlated with repeat length when intermediate HD expansions are considered. Recently, suggestive association has been reported between a single nucleotide polymorphism (SNP; rs1801131, also known as A1298C) in the methyltetrahydrofolate reductase (MTHFR) gene and AO of HD. 5,10-MTHFR is a key enzyme in the folate metabolism, diverting metabolites toward methylation reactions or nucleotide synthesis. Using part of a previously established study cohort plus additional patients and appropriate statistical methods, we reinvestigated two polymorphisms in the MTHFR gene, C677T and A1298C, as well as their association with AO in 167 HD patients.
Results
There was no statistically significant impact on AO for HD patients, neither of MTHFR SNPs nor of the combinations thereof.
Conclusion
Contrary to previously described evidence the A1298C polymorphism in the MTHFR gene does not appear to modulate AO of HD patients.
doi:10.1186/1477-5751-4-12
PMCID: PMC1327683  PMID: 16372906
20.  On the genetic involvement of apoptosis-related genes in Crohn's disease as revealed by an extended association screen using 245 markers: no evidence for new predisposing factors 
Crohn's disease (CD) presents as an inflammatory barrier disease with characteristic destructive processes in the intestinal wall. Although the pathomechanisms of CD are still not exactly understood, there is evidence that, in addition to e.g. bacterial colonisation, genetic predisposition contributes to the development of CD. In order to search for predisposing genetic factors we scrutinised 245 microsatellite markers in a population-based linkage mapping study. These microsatellites cover gene loci the encoded protein of which take part in the regulation of apoptosis and (innate) immune processes. Respective loci contribute to the activation/suppression of apoptosis, are involved in signal transduction and cell cycle regulators or they belong to the tumor necrosis factor superfamily, caspase related genes or the BCL2 family. Furthermore, several cytokines as well as chemokines were included. The approach is based on three steps: analyzing pooled DNAs of patients and controls, verification of significantly differing microsatellite markers by genotyping individual DNA samples and, finally, additional reinvestigation of the respective gene in the region covered by the associated microsatellite by analysing single-nucleotide polymorphisms (SNPs). Using this step-wise process we were unable to demonstrate evidence for genetic predisposition of the chosen apoptosis- and immunity-related genes with respect to susceptibility for CD.
doi:10.1186/1477-5751-4-8
PMCID: PMC1315346  PMID: 16318629
21.  Age at onset of Huntington disease is not modulated by the R72P variation in TP53 and the R196K variation in the gene coding for the human caspase activated DNase (hCAD) 
BMC Medical Genetics  2005;6:35.
Background
TP53 is an attractive candidate for modifying age of onset (AO) in Huntington disease (HD): The amino-terminus of the mutated huntingtin (htt) exon 1 translation product has functional properties which may affect critically the TP53 pathway in HD neurons. The pathogenic domain of mutant htt interacts with nuclear transcription factors, and it potentially modulates TP53-induced transcriptional events. A single nucleotide polymorphism (SNP) resulting in the R72P exchange in TP53 protein might modulate the variation in AO. In addition, also the R196K replacement in human caspase activated DNase (hCAD) may theoretically affect the AO.
Methods
We have genotyped the polymorphisms R72P and R196K in a well established cohort of 167 unrelated HD patients.
Results
The expanded CAG repeat explained 30.8% of the variance in AO. Adding the genotypes of the SNPs investigated did not affect the variance of the AO variance explained.
Conclusion
In this replication study, no association was found explaining a significant amount of the variability in AO of HD thus contradicting a recent report.
doi:10.1186/1471-2350-6-35
PMCID: PMC1253512  PMID: 16202123
22.  Evaluation of the toll-like receptor 6 Ser249Pro polymorphism in patients with asthma, atopic dermatitis and chronic obstructive pulmonary disease 
BMC Medical Genetics  2005;6:34.
Background
For allergic disorders, the increasing prevalence over the past decade has been attributed in part to the lack of microbial burden in developed countries ('hygiene hypothesis'). Variation in genes encoding toll-like receptors (TLRs) as the receptor system for the first innate immune response to microbial stimuli has been implicated in various inflammatory diseases. We evaluated here the role of a coding variation, Ser249Pro, in the TLR6 gene in the pathogenesis of asthma, atopic dermatitis (AD) and chronic obstructive pulmonary disease (COPD).
Methods
Genotyping of the Ser249Pro polymorphism in 68 unrelated adult patients and 132 unrelated children with asthma, 185 unrelated patients with COPD, 295 unrelated individuals with AD and 212 healthy control subjects was performed by restriction enzyme digestion.
Results
We found a weak association of the 249Ser allele with childhood asthma (p = 0.03). Yet, significance was lost after Bonferroni correction. No association was evident for AD or COPD.
Conclusion
Variation in TLR6 might play a role in the pathogenesis of childhood asthma.
doi:10.1186/1471-2350-6-34
PMCID: PMC1262722  PMID: 16188043
23.  An extended association screen in multiple sclerosis using 202 microsatellite markers targeting apoptosis-related genes does not reveal new predisposing factors 
Apoptosis, the programmed death of cells, plays a distinct role in the etiopathogenesis of Multiple sclerosis (MS), a common disease of the central nervous system with complex genetic background. Yet, it is not clear whether the impact of apoptosis is due to altered apoptotic behaviour caused by variations of apoptosis-related genes. Instead, apoptosis in MS may also represent a secondary response to cellular stress during acute inflammation in the central nervous system. Here, we screened 202 apoptosis-related genes for association by genotyping 202 microsatellite markers in initially 160 MS patients and 160 controls, both divided in 4 sets of pooled DNA samples, respectively. When applying Bonferroni correction, no significant differences in allele frequencies were detected between MS patients and controls. Nevertheless, we chose 7 markers for retyping in individual DNA samples, thereby eliminating 6 markers from the list of candidates. The remaining candidate, the ERBB3 gene microsatellite, was genotyped in additional 245 MS patients and controls. No association of the ERBB3 marker with the disease was detected in these additional cohorts. In consequence, we did not find further evidence for apoptosis-related genes as predisposition factors in MS.
doi:10.1186/1477-5751-4-7
PMCID: PMC1215511  PMID: 16143043
24.  Long-term fitness consequences of female extra-pair matings in a socially monogamous passerine. 
Whether female birds choose extra-pair mating partners to obtain genetic fitness benefits is intensely debated. The most straightforward and crucial test of 'good genes' models of female extra-pair mating is the comparison of naturally 'cross-fostered' maternal half-siblings sharing the same rearing environment as any systematic differences in performance between the two categories of offspring phenotype can be attributed to differential paternal genetic contribution. We analysed local recruitment and first-year reproductive performance of maternal half-siblings in the coal tit (Parus ater), a passerine bird with high levels of extra-pair paternity. We provide a highly comprehensive measure of the long-term fitness consequences of female extra-pair matings based on a large sample of 736 within-pair offspring (WPO) and 368 extra-pair offspring (EPO) from 91 first and 55 second broods, from which 132 breeders recruited into the study population. In contrast to predictions derived from 'good genes' models, we found no differences in local recruitment and seven parameters of first-year reproductive performance when comparing WPO and EPO. These results question the universal validity of findings in other bird species supporting 'good genes' models, particularly as they are based on the best approximation to female fitness obtained so far.
doi:10.1098/rspb.2002.2216
PMCID: PMC1691239  PMID: 12614574
25.  Glutathione S-Transferase Ω 1 variation does not influence age at onset of Huntington's disease 
Background
Huntington's disease (HD) is a fully penetrant, autosomal dominantly inherited disorder associated with abnormal expansions of a stretch of perfect CAG repeats in the 5' part of the IT15 gene. The number of repeat units is highly predictive for the age at onset (AO) of the disorder. But AO is only modestly correlated with repeat length when intermediate HD expansions are considered. Circumstantial evidence suggests that additional features of the HD course are based on genetic traits. Therefore, it may be possible to investigate the genetic background of HD, i.e. to map the loci underlying the development and progression of the disease. Recently an association of Glutathione S-Transferase Ω 1 (GSTO1) and possibly of GSTO2 with AO was demonstrated for, both, Alzheimer's (AD) and Parkinson's disease (PD).
Methods
We have genotyped the polymorphisms rs4925 GSTO1 and rs2297235 GSTO2 in 232 patients with HD and 228 controls.
Results
After genotyping GSTO1 and GSTO2 polymorphisms, firstly there was no statistically significant difference in AO for HD patients, as well as secondly for HD patients vs. controls concerning, both, genotype and allele frequencies, respectively.
Conclusion
The GSTO1 and GSTO2 genes flanked by the investigated polymorphisms are not comprised in a primary candidate region influencing AO in HD.
doi:10.1186/1471-2350-5-7
PMCID: PMC394327  PMID: 15040808

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