ABSTRACT
Massively parallel sequencing (MPS) of identity informative single-nucleotide polymorphisms (IISNPs) enables hundreds of forensically relevant markers to be analysed simultaneously. Generating DNA sequence data enables more detailed analysis including identification of sequence variations between individuals. The GeneRead DNAseq 140 IISNP MPS panel (QIAGEN) has been evaluated on both the MiSeq (Illumina) and Ion PGM™ (Applied Biosystems) MPS platforms using the GeneRead DNAseq Targeted Panels V2 library preparation workflow (QIAGEN). The aims of this study were to (1) determine if the GeneRead DNAseq panel is effective for identity testing by assessing deviation from Hardy-Weinberg (HWE) and pairwise linkage equilibrium (LE); (2) sequence samples with the GeneRead DNAseq panel on the Ion PGM™ using the QIAGEN workflow and assess specificity, sensitivity and accuracy; (3) assess the efficacy of adding biological samples directly to the GeneRead DNAseq PCR, without prior DNA extraction; and (4) assess the effect of varying coverage and allele frequency thresholds on genotype concordance. Analyses of the 140 SNPs for HWE and LE using Fisher's exact tests and the sequential Bonferroni correction revealed that one SNP was out of HWE in the Japanese population and five SNP combinations were commonly out of LE in 13 of 14 populations. The panel was sensitive down to 0.3125 ng of DNA input. A direct-to-PCR approach (without DNA extraction) produced highly concordant genotypes. The setting of appropriate allele frequency thresholds is more effective for reducing erroneous genotypes than coverage thresholds.
Subject(s)
High-Throughput Nucleotide Sequencing/instrumentation , Polymorphism, Single Nucleotide , Sequence Analysis, DNA , Animals , Ethnicity/genetics , Gene Frequency , Genotype , Humans , Linkage Disequilibrium , Polymerase Chain Reaction , Racial Groups/genetics , Sensitivity and Specificity , Species SpecificityABSTRACT
BACKGROUND: Human Paneth cell alpha-defensins, especially DEFA5, are involved in maintaining homeostasis of the human microbial microflora. Since breakdown of normal mucosal antibacterial defence occurs in inflammatory bowel disease (IBD), variants in the DEFA5 gene could be associated with IBD risk. SUBJECTS: A cohort of 25 patients with indeterminate colitis (IC), 405 with ulcerative colitis (UC), and 385 with Crohn's disease (CD), were compared with 201 control individuals from the Canterbury region in New Zealand. METHODS: A 15 kb haplotype block surrounding DEFA5 contained 35 HapMap markers which were polymorphic in Caucasians. Four markers (A-D) were selected to tag 27 of the 35 markers at r(2)>0.68, and were genotyped in DNA samples. RESULTS: Minor allele frequencies for all single nucleotide polymorphisms (SNPs) were somewhat elevated in patients. Subgroup analysis showed SNP A had odds ratio 1.44 in UC patients with pancolitis (95% C.I. 1.07-1.94), SNP B odds ratio 2.37 in CD patients with onset prior to 17 years age (95% C.I. 1.12-5.03), SNP C odds ratio 1.68 in UC patients with left colonic localisation (95% C.I. 1.12-2.52), and SNP D had odds ratio 1.56 in CD patients with one or more relatives with IBD (95% C.I. 1.03-2.35). Two two-marker haplotypes and one three-marker haplotype were associated with UC (p-values 0.025-0.05). CONCLUSIONS: The SNPs genotyped in our study were surrogates for common variants, and observed associations between these and IBD status are likely due to linkage disequilibrium with a functional common DEFA5 variant. Identifying such functional variants will be prioritized in subsequent work.
Subject(s)
Genetic Predisposition to Disease , Inflammatory Bowel Diseases/ethnology , Inflammatory Bowel Diseases/genetics , Polymorphism, Single Nucleotide , White People/genetics , alpha-Defensins/genetics , Adult , Case-Control Studies , Cohort Studies , Colitis, Ulcerative/epidemiology , Colitis, Ulcerative/genetics , Colitis, Ulcerative/pathology , Confidence Intervals , Crohn Disease/epidemiology , Crohn Disease/genetics , Crohn Disease/pathology , Female , Gene Frequency , Genotype , Haplotypes , Humans , Inflammatory Bowel Diseases/pathology , Linkage Disequilibrium , Male , Middle Aged , New Zealand/epidemiology , Odds Ratio , Paneth Cells/pathology , Paneth Cells/physiology , ProbabilityABSTRACT
BACKGROUND: DLG5 p.R30Q has been reported to be associated with Crohn disease (CD), but this association has not been replicated in most studies. A recent analysis of gender-stratified data from two case-control studies and two population cohorts found an association of DLG5 30Q with increased risk of CD in men but not in women and found differences between 30Q population frequencies for males and females. Male-female differences in population allele frequencies and male-specific risk could explain the difficulty in replicating the association with CD. METHODS: DLG5 R30Q genotype data were collected for patients with CD and controls from 11 studies that did not include gender-stratified allele counts in their published reports and tested for male-female frequency differences in controls and for case-control frequency differences in men and in women. RESULTS: The data showed no male-female allele frequency differences in controls. An exact conditional test gave marginal evidence that 30Q is associated with decreased risk of CD in women (p = 0.049, OR = 0.87, 95% CI 0.77 to 1.00). There was also a trend towards reduced 30Q frequencies in male patients with CD compared with male controls, but this was not significant at the 0.05 level (p = 0.058, OR = 0.87, 95% CI 0.74 to 1.01). When data from this study were combined with previously published, gender-stratified data, the 30Q allele was found to be associated with decreased risk of CD in women (p = 0.010, OR = 0.86, 95% CI 0.76 to 0.97), but not in men. CONCLUSION: DLG5 30Q is associated with a small reduction in risk of CD in women.
