Two APOL1 alleles have been shown to be strongly associated with focal segmental glomerulosclerosis and end-stage renal disease in African Americans, Hispanic Americans and in individuals of African descent. The APOL1 G1 allele, defined by the derived alleles of coding SNPs rs73885319 (p.S342G) and rs60910145 (p.I384M), and the APOL1 G2 allele, defined by the derived allele for indel rs71785313 (p.NYK388K). [PMID 20647424] and [PMID 20635188].
Customers of 23andMe can use the presence of the A allele for coding SNP rs2239785 (p.E150K) or the presence of the G allele for coding SNP rs136175 (p.M228I) or coding SNP rs136176 (p.R255K) to exclude the presence of alleles G1 and G2, although absence of these alleles does not imply presence of either G1 or G2. Furthermore, presence of the T allele for SNP rs4419330 excludes the presence of allele G2 and presence of the C allele for SNP rs4419330 excludes the presence of allele G1.
In 2017, a study of US African-Americans addressed the question of why only about half of the 15 to 20 percent of blacks carrying G1 and G2 mutations actually go on to develop chronic kidney disease. They concluded that high plasma levels of a certain protein, soluble urokinase plasminogen activator receptor (suPAR), predicted the individuals at higher risk, and that smoking, weight gain and even frequent infections can add up and send suPAR to high levels. Weight loss and smoking cessation can help bring levels down, but once elevated, suPAR may not recede to a healthy level again, so individuals carrying G1 and G2 mutations should aim to live a healthy life to keep suPAR levels low.[PMID 28650456]