Expression of the mouse Aven gene during spermatogenesis, analyzed by subtraction screening using Mvh-knockout mice.

As an attempt to investigate the function of the mouse Vasa-homolog (MVH) protein, a germ cell-specific RNA helicase, we have cloned genes that fail to be expressed in homozygous Mvh-knockout testes. One of the cDNA clones obtained by selective PCR subtraction cloning matched two cDNA sequences in the mouse testis cDNA database, and was highly homologous to Aven, a human gene regulating cell death. Sequences of the two mouse testis cDNAs in the database revealed that they share an 800 bp sequence but have quite different 5'-regions; the latter are derived from different exons by alternative use of transcription initiation sites. The shorter (mAven-S) and longer (mAven-L) transcripts encode 216 and 342 amino acids, respectively, and both isoforms are predominantly expressed in adult testes. However, mAven-L is not completely testis-specific and is expressed in testes during all developmental stages, whereas the expression of mAven-S is restricted to the testis and is barely detectable in Mvh-homozygous testes. In situ hybridization showed that mAven-S is expressed specifically in post-meiotic cells, mainly in round spermatids.