Widespread Divergence of the CEACAM/PSG Genes in Vertebrates and Humans Suggests Sensitivity to Selection

Chang, Chia Lin; Semyonov, Jenia; Cheng, Po Jen; Huang, Shang Yu; Park, Jae Il; Tsai, Huai-Jen; Lin, Cheng-Yung; Grützner, Frank; Soong, Yung Kuei; Cai, James J.; Hsu, Sheau Yu Teddy

Whereas there are at least 387 unique CNVs that are larger than 500 bp (range from 0.5 to 379 kb) on chromosome 19, 14 of them affected the CEACAM/PSG locus. Of the 46 CNVs that encompassed a .20-kb region, a disproportionate 17.4% (8 out of 46 CNVs) of them were located at the CEACAM/PSG locus (Fig. 5b) . Three of these CNVs actually represented the longest gains or losses of chromosome segment on chromosome 19, and all these CNVs affected multiple PSG genes: CNVR3824.1 (379 kb, encompassing PSG1, 2, 6, 7, 10, and 11), CNVR7658.2 (238 kb, including PSG1, 6, 7, 10, and 11), and CNVR7658.5 (252 kb, including PSG2, 4, 5, and 9)( Table S5 in File S1). Among CNVs, those have a frequency higher than 1% are distinguished as copy number polymorphisms. Based on this criterion, almost all CEACAM/PSG CNVs represented common copy number polymorphisms (.3% frequency) that have been retained in recent human history. Furthermore, we estimated that the copy number of PSG genes could range from 12 copies in individuals who are homozygous for gene loss at CNVR7658.2 to 30 copies in individuals with homozygous gene gains at CNVR7658.5, instead of 22 copies found in most individuals.