Supplementary Material for: Synaptonemal Complex Protein SYCP3 Exists in Two Isoforms Showing Different Conservation in Mammalian Evolution

Meiosis-specific protein SYCP3 is a major structural component of synaptonemal complex (SC) lateral elements. SYCP3 is rather well conserved in vertebrates. However, some differences in SYCP3 expression have been shown among mammals. To clarifiy these differences, we have investigated SYCP3 expression with the aid of bioinformatic, biochemical and cell biological methods. Here we show that, in contrast to other vertebrates, rat and mouse SYCP3 exist in 2 isoforms. The short isoform is conserved among vertebrates. However, the longer isoform, which represents an N-terminal extension of the shorter one, most likely appeared about 15 million years ago in a common ancestor of rat and mouse and after separation from the hamster branch.