Diverse Fates of Paralogs Following Segmental Duplication of Telomeric Genes

The telomeric region of chromosome 9p is paralogous to the pericentromeric regions of chromosome 9 as well as to 2q13, the site of an ancestral telomere-telomere fusion. These paralogous regions span approximately 200 kb and contain seven transcriptional units, including the previously identified CBWD, FOXD4, PGM5, F379, CXYorf1, and two human Unigene clusters, Hs.115173 and Hs.189160. Within these gene duplicates, the number of expressed paralogous loci varies, from one in PGM5 to all three in CBWD and Hs.115173. FOXD4 shows the most dramatic changes among its paralogs. Two independent insertion/deletion changes created four different carboxy ends of these intronless genes, two of which are within the 2q13 locus. A comparison of KA/KS values among functional paralogs shows these genes evolved rapidly in primates. This study shows the importance of paralogous regions in the generation of transcriptional diversity and highlights the significance that large-scale telomeric duplication may play in this process.