Molecular evolution of TEPP protein genes in metazoans

TEPP is a gene expressed in human reproductive organs such as testis, prostate, and placenta. Here, identification and molecular evolutionary analysis of TEPP proteins in various metazoan animals including deuterostomes (chordates, hemichordates, and echinoderms), lophotrochozoans (mollusks and annelids), and cnidarians (sea anemone and coral) are reported. A multiple sequence alignment revealed two highly conserved regions in TEPP proteins that had no similarity to any other known domains or proteins. Genomic sequence analysis showed frequent shifting of the splice sites of intron 1 in mammalian TEPP genes. A comparison of the intron positions in the coding region showed that the exon/intron structure of the TEPP gene was established in an early metazoan ancestor and that independent loss of a single intron occurred in echinoderms and in vertebrates. The urochordate tunicate TEPP genes are intronless, possibly due to replacement of the original gene by a retrogene. No homolog was detected in birds, insects, nematodes, and teleost fishes despite the extensive sequence data of these species, implying that the TEPP gene might be lost in these lineages.