Sequential loss of two neighboring exons of the tropoelastin gene during primate evolution

Previous evidence has demonstrated the absence of exons 34 and 35 within th e 3' end of the human tropoelastin (ELN) gene. These exons encode conserved polypeptide domains within tropoelastin and are found. in the ELN gene in vertebrate species ranging from chickens to rats to cows. We have analyzed the ELN gene in a variety of primate species to determine whether the absen ce of exons 34 and 35 in humans either is due to allelic variation within t he human population or is a general characteristic of the Primates order. A n analysis of the 3' end of the ELN gene in several nonhuman primates and i n 546 chromosomes from humans of varying ethnic background demonstrated a s equential loss of exons 34 and 35 during primate evolution. The loss of exo n 35 occurred at least 35-45 million years ago, when Catarrhines diverged f rom Platyrrhines (New World monkeys). Exon 34 loss, in contrast, occurred o nly about: 6-8 million years ago, when Homo separated from the common ances tor shared with chimpanzees and gorillas. Loss of both exons was probably f acilitated by Alu-mediated recombination events and possibly conferred a fu nctional evolutionary advantage in elastic tissue.