Figure 1.
Differences in genetic risk among populations.
Each population is ranked by risk, which is denoted by a color. Populations with the greatest risk are bright red, and those with the lowest risk are green. (A) Populations for East Asia and the Americas have lower genetic risk for type 2 diabetes than those from Africa and Europe. Genetic risk differentiation is sharply divided along major population migration events. Type 2 diabetes is represented by 16 SNPs. (B) Genetic risk for biliary liver cirrhosis is represented by 44 SNPs. Genetic risk peaks in East Asia and in the Karitiana population in South America. The background is a public domain world map from NASA Earth Observatory (http://eoimages.gsfc.nasa.gov/images/imagerecords/73000/73909/world.topo.bathy.200412.3×5400×2700.jpg); an interactive online tool is available at http://geneworld.stanford.edu using Google Maps technology.
Figure 2.
Genetic risk in the context of human relationships.
The figure superimposes genetic risk for type 2 diabetes on a maximum likelihood phylogenetic tree based on the HGDP. Branch color indicates whether the subtree has shifted towards increased or decreased risk (q-value<0.05). Red∶increased risk; green∶decreased risk. Each colored branch also represents an independent genetic risk differentiation event as determined by a maximum likelihood model. Numbers in colored rectangles show percentile of genetic risk, with a zero being lowest. (A) Type 2 diabetes risk was decreased in East Asia and America. (B) Biliary Liver Cirrhosis shifted towards increased genetic risk in the Japanese population and towards decreased risk in the Druze population. The Karitiana population also showed borderline signs of genetic risk differentiation (q = 0.057).
Table 1.
List of populations with disease risk differentiation.
Figure 3.
Variability in genetic risk for type 2 diabetes.
Individuals are represented by vertical multicolored rectangles. Individual bars in each rectangle represent one of the 16 SNPs associated with type 2 diabetes. Bar colors indicate the following: red: homozygosity for a risk allele; blue∶heterozygosity; green∶homozygosity for a protective allele; white: missing genotype. The order of the SNPs is preserved across individuals. The x-axis shows genetic risk and the y-axis shows each population. The purple line is a locally weighted linear regression curve displaying the general direction of disease susceptibility as populations migrated from West to East. Genetic risk is lower in East Asians.
Figure 4.
Variability in genetic risk in biliary liver cirrhosis.
Individuals are represented by vertical multicolored rectangles. Bar colors indicate the following: red: homozygosity for a risk allele; blue: heterozygosity; green: homozygosity for a protective allele; white: missing genotype. The x-axis shows risk and the y-axis shows each population. The purple line is a locally weighted linear regression curve displaying the general direction of disease susceptibility as populations migrated from West to East. No trend is obvious, but risk appears to be higher in Cambodian, Yizu, Japanese, and San populations.
Figure 5.
Expected amount of genetic risk differentiation in ulcerative colitis.
Random variation caused by genetic drift may alter genetic risk between populations. The figure represents the expected amount of genetic risk difference between Sindhi and all other populations. A randomly generated genetic risk score was computed by randomly picking SNPs to represent ulcerative colitis (see Materials and Methods). The red vertical line represents the observed genetic difference between the Sindhi and all other populations combined. Only 15 out of 100,000 randomly generated genetic risk values had a larger genetic risk difference than the observed.