Analysis of 5'-end Sequences of Full-length cDNAs obtained from Chimpanzee Skin Tissues.

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We constructed full-length enriched cDNA libraries from chimpanzee skin and brain tissues by the oligo-capping method to establish a database of sequences of chimpanzee genes. The objective of this study was to precisely calculate sequence diversity between human and chimpanzee homologs. In addition, a comparative analysis of tissue-specific expressions of genes between humans and chimpanzees is expected to shed light on species specificity and evolution of humans. Randomly selected clones from the libraries were subjected to one-pass sequencing from their 5'-ends. As a result, we collected 6813 chimpanzee cDNA sequences longer than 400 bp. Homology search against human mRNA sequences (RefSeq mRNAs) revealed that our collection included sequences of 1652 putative chimpanzee genes. It was evident that the spectra of expressed genes in skin and brain tissues were different. For instance, in skin, keratin, vimentin and decorin genes were prominent. In order to calculate the sequence identity between human and chimpanzee homologs, we constructed 5'-end consensus sequences of 226 chimpanzee genes by aligning at least three sequences for individual genes. Sequence identity was estimated by comparing these consensus sequences and the corresponding sequences of their human homologs. The average sequence identity of the 5'-end cDNAs was 99.30%. Those of the 5'-UTRs and CDSs were 98.79% and 99.42%, respectively. The results confirmed that human and chimpanzee genes are highly conserved at the nucleotide level. As for amino acids, the average sequence identity was 99.44%. The average synonymous (KS) and nonsynonymous (KA) divergences were estimated to be 1.33% and 0.28%, respectively. Our collection of full-length cDNA clones and sequence data could be a valuable resource for postgenomic research.