Comparative analysis of the PCOLCE region in Fugu rubripes using a new automated annotation tool

Abstract.

The Japanese pufferfish Fugu rubripes with a genome of about 400 Mb is becoming increasingly recognized as a vertebrate model organism for comparative gene analysis (see Elgar 1996 for review). We have isolated and sequenced two Fugu cosmids spanning a genomic region of 66 kb containing the Fugu homolog to the human PCOLCE-I (Glöckner et al. 1998). We then examined if RUMMAGE-DP, a newly developed analysis tool for gene discovery which was designed for human and mouse genomic DNA, can be used for automatic annotation of Fugu genomic sequence. The exon prediction programs contained in RUMMAGE-DP performed better overall for the human sequence than for the Fugu contig. The GENSCAN program was the only exon prediction programme that performed equally well for both organisms. We show that RUMMAGE-DP is very useful in automatic analysis of Fugu sequences. Comparative analysis of the genomic structure of the PCOLCE-I genes in Fugu and human reveals that the exon/intron structure throughout the protein coding region is almost identical. We defined an additional domain based on the high degree of similarity of 26 aa between mammals and Fugu. The PCOLCE-I protein in both organisms contains two highly conserved CUB domains. Exons 6 and 7 are the only coding exons that differ in length between the two species. We assume that these exons do not code for any catalytic domain of the protein. Analysis of the remaining five Fugu genes within the 66 kb interval revealed no conserved synteny with the corresponding human 7q22 region.