We are pleased to announce four new features in the
Type 2 Diabetes Knowledge Portal that simplify the interpretation of genetic association data, making it easier to pinpoint variants and datasets that are informative for a disease or phenotype of interest.
"Clumping" variants by linkage disequilibrium
The first step in getting an overview of the results of a particular experiment is typically to plot variant associations vs. chromosomal location, in a so-called "Manhattan plot." These plots are available from the T2DKP home page after choosing a phenotype from the list:
After selecting a phenotype, you may select a dataset, and the Manhattan plot is displayed above a table of the top variants:
Now, in addition to selecting a dataset to view associations, you may select a threshold for linkage disequilibrium (LD) in order to reduce the number of linked variants that represent a single association signal. For example, without "clumping" variants by LD (r
2 = 1), when viewing the DIAGRAM 1000G GWAS dataset there are 70 significantly associated variants in the
IGFBP2 gene; but setting the most stringent LD threshold (r
2 = 0.1) reduces that number to just 8 variants by displaying only the most significant associations after clumping variants by LD. Intermediate LD thresholds of r
2 = 0.2. 0.4, 0.6, or 0.8 may also be set, allowing more versatility in this analysis.
New Region page
The Gene page of the T2DKP (
see an example) integrates and summarizes information about the associations of variants across the region of a gene. Now, you can see this integration and summation for any region of the genome, not just the areas surrounding protein-coding genes. Simply enter a chromosome and coordinates in the home page search box:
The resulting page resembles a Gene page. The traffic light integrates all associations across the region to give you an immediate indication of whether there are significant associations found in any of the datasets in the T2DKP. Further down the page, tools and displays let you drill down to the specifics for a phenotype or variant of interest. This new Region page provides a way to explore any part of the genome in great detail.
PheWAS graphic on the Variant page
Previously, the Variant page of the T2DKP displayed significant associations for each variant in a graphic that showed a color-coded box for each phenotype-dataset combination. But the rapidly increasing number of phenotypes becoming available from biobank studies has made this view unsustainably large. In its place, we have incorporated a phenome-wide association study (
PheWAS) visualization developed at the University of Michigan. The graphic shows at a glance which phenotype associations are most significant for a particular variant. Mouse over a point to see more details.
All Associations graphic on the Variant page
The PheWAS graphic distills variant associations in order to highlight the most significant ones. But suppose you want to drill down to the details and explore associations in every dataset, viewing parameters like sample size, odds ratio, and more? There's a graphic for that too: our new All Associations interactive graphic, located in the "Associations across all datasets" section of the variant page. Start by using keywords to filter phenotypes. Filtering allows you to view one specific phenotype, several related phenotypes, or phenotypes in a broad category, such as glycemic phenotypes; both the graphic and the table below it change in response to phenotype filtering. There are also options to filter by setting ranges of p-values and/or sample sizes.
The graph plots p-value (vertical axis) vs. dataset sample size (horizontal axis) for each association. Points in the graph are triangular; whether the triangle points up or down indicates a positive or negative direction of effect, respectively. Mousing over a point shows you more details about the association and the dataset. This graphic can help you evaluate whether an association is likely to be real. As shown in the illlustration below, a genuine signal should increase in significance (
i.e., decrease in p-value) with increasing sample size.
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