Patterns of any AMD-related SNPs in the global population and in East Asians
We collected 232 AMD-associated SNPs from 24 GWASs from the NHGRI-EBI GWAS catalog. The SNPs were identified in 17 European populations, four East Asian populations, and three South Asian populations; three studies were performed in mixed ethnic populations. Clearly, populations other than Europeans were understudied, particularly African and American populations. However, there were no significant differences in the SNP frequencies among these populations (Figure 1). This result suggested that many SNPs found in Europeans were also applicable to other populations. After collecting 138 AMD-associated SNPs, we determined the effect allele frequencies (EAFs) for each of the continental groups and for Koreans based on genotype information from the 1000 Genomes Project and KRGDB (Supplementary Table S1). Heatmap analysis showed how significantly the effect allele was enriched or depleted across the Korean and continental groups (Supplementary Figure 1). For Koreans, 55 AMD-related SNPs were significantly enriched, 74 SNPs were depleted, and nine SNPs were similar to the global EAFs. Additionally, heatmap analysis enabled visualization of the proportion of effect alleles in each continental group compared with the global average. For example, rs5754227 (SYN3), rs1626340 (TGFBR1/COL15A1), rs3750846 (ARMS2/HTRA1), and rs9564692 (B3GALTL) were enriched, whereas rs2230199 (C3) and rs73036519 (EXOC3L2/MARK4) were depleted in Koreans. The hierarchical clustering tree showed differences among the populations; Europeans, Americans, and South Asians were in one cluster, whereas Africans, East Asians, and Koreans were in another cluster.
Next, we compared the EAFs of East Asians and Koreans (Supplementary Table S2 and Figure 2). Although the EAF did not differ much among East Asians, 21 SNPs were enriched, 30 SNPs were depleted, and 87 SNPs were similar to those in Koreans. Moreover, the heatmap clearly showed that the main allele frequency pattern in East Asians in the 1000 Genomes Project was similar to that in Koreans; in contrast, few alleles showed the opposite allele frequency patterns between East Asians and Koreans.
Patterns of late AMD-related SNPs in the global population and in East Asians
Thirty-one SNPs related to late AMD were selected from 138 AMD-related SNPs (Table 1), and a heatmap showing how significantly the EAF was enriched or depleted across the Koreans and continental groups (Figure 2) with a log scale among 31 late AMD-related SNPs was generated. For Koreans, 10 AMD-related SNPs were significantly enriched, 19 SNPs were depleted, and two SNPs were similar to global EAFs. For example, rs11080055, located in the intronic region of the TMEM97 gene, which encodes transmembrane protein 97, had A>C alleles; the C allele was detected in 49% of Europeans and 76% of Koreans. Additionally, rs1626340, located in the intergenic region of TGFBR1/COL15A1, which encodes collagen type XV alpha 1 chain, had G>A alleles; the A allele was detected in 21% of Europeans and 51% of Koreans. This SNP has been reported to be associated with various diseases, including colon cancer.[25, 26] rs5754227, located in the intronic region of SYN3 which encodes synapsin-3 (a neuronal phosphoprotein associated with the cytoplasmic surface of synaptic vesicles), had T>C alleles; the C allele frequencies were 13% for Europeans and 67% for Koreans. Some SNPs were depleted in Koreans. For example, rs73036519, located in the intergenic region of the EXOC3L2/MARK4 gene, which encodes a member of the microtubule affinity-regulating kinase family, had G>C alleles; the C allele frequencies were 29% for Europeans and 0% for Koreans. Hierarchical clustering tree analysis showed differences among the populations; Europeans, Americans, and South Asians were in one cluster, whereas Africans, East Asians, and Koreans were in another cluster (Figure 2).
In addition, heatmap analysis showed differences in EAFs across Koreans and East Asians (Table 2, Figure 3). The rs61818925, located in the intergenic region of the CFHR1 gene, which encodes complement factor H, had T>G alleles; the G allele frequencies were 33% for Chinese populations and 50% for Koreans. Notably, some SNPs were depleted in Koreans; for example, rs12019136, located in the intronic region of the C3 gene, which encodes complement C3, had G>A alleles; the A allele frequencies were 21% for Vietnamese populations and 8% for Koreans. However, the EAFs did not differ substantially among East Asians; for Koreans, four SNPs were enriched, 11 SNPs were depleted, and 16 SNPs were similar to those in global East Asian populations.
Genetic risk scores calculated using SNPs related to any AMD and late AMD
Next, we calculated the composite genetic risk scores based on copies of effect alleles at AMD-associated SNPs, with the assumption that allelic associations from most GWAS-identified variants could be replicated in non-European populations [27]. The genetic risk score of any AMD was highest in East Asians, followed by South Asians, Americans, and Europeans (Figure 4). The prevalence of any AMD in individuals 65 years old or older was correlated with the population average genetic risk score (R = 0.864; Figure 5). In addition, the genetic risk score of late AMD was highest in East Asians, followed by Europeans, Americans, and South Asians (Figure 4). However, differences in genetic risk scores of late AMD were not greater than those of any AMD, as supported by meta-analysis data indicating that the prevalence of late AMD was similar among Europeans and Asians [7]. The prevalence of late AMD in individuals 40 years old or older was correlated with the population average genetic risk score (R = 0.558; Figure 5). In addition, the PRS of any AMD or late AMD in East Asians was similar among Europeans and Asians (Supplementary Figure S3). The prevalence of any AMD in individuals 65 years old or older was correlated with the population PRS (R = 0.846; Supplementary Figure S3) and the prevalence of late AMD in individuals 40 years old or older was correlated with the population PRS (R = 0.572; Supplementary Figure S3).