Figure 6. Positive natural selection has shaped CD4 polymorphism in SIV-endemic ape species.

(A) Mean and standard error of mean of synonymous and nonsynonymous nucleotide heterozygosity (Θπ) at CD4 and neighboring loci across species endemically infected with SIV (chimpanzee and gorilla) or un/recently infected (human, bonobo and orangutans). Schematic along the bottom of each graph depicts the relative location of each locus as follows 5’ to 3’: ZNF384, PIANP, COPS7A, MLF2, PTMS, CD4, GPR162, GNB3, CDCA3, TPI1, LRRC23, and EN02. Mann-Whitney test indicates whether heterozygosity at CD4 is significantly different than neighboring loci. (B) Schematic of CD4 domain regions. Ticks above and below the CD4 box indicate the location of polymorphic sites for the infected and un/recently infected species groups, respectively. One of the polymorphic residues in gorilla contains two nonsynonymous changes in a single codon, marked by a star above the tick. (C) 2x2 contingency table and test results comparing synonymous and nonsynonymous polymorphism location relative to domain 1 between infected and un/recently infected species.