OTT A MOUSE X-LINKED MULTIGENE FAMILY EXPRESSED SPECIFICALLY DURING MEIOSIS

The tissue expression patterns of 10 mouse testis cDNAs were analysed by RT-PCR to search for new mammalian meiotic genes, The homologue of the rat synaptonemal complex protein gene SCP1 is expressed in embryon ic ovary, adult brain and testis, One novel gene is stringently testis specific and another is expressed exclusively in testis and embryonic ovary, The latter clone is not expressed in the testes of adult sex-r eversed mice which lack germ cells, and therefore represents a meiosis -specific gene, It is part of a mouse multigene family, members of whi ch are clustered and map genetically and physically to a single region of the X chromosome. We have named this family Ott (ovary testis tran scribed), Steady-state levels of a 2.3 kb polyadenylated Ott mRNA are high throughout meiotic prophase in the testis when the X chromosome i s generally transcriptionally inactive. A second transcript of 1 kb is also detectable from 4 weeks of age onwards. The two mRNAs have diffe rent 3' ends and contain different protein coding information, At leas t seven Ott genes are transcribed specifically during meiosis and are predicted to encode 'pioneer' proteins with an unusual structure, cont aining tandem arrays of a degenerate eight amino acid repeat, This wor k could lead to the identification of a human Ott homologue, which is likely to be X-linked and would provide a candidate locus for some cas es of male infertility.