Identification of a new expanding family of genes characterized by atypical LRR domains. Localization of a cluster preferentially expressed in oocyte.

In the present work, we have used the in silico subtraction methodology to identify novel oocyte-specific genes in the mouse. By this way, we have identified in silico a new family of genes composed of more than 80 members. Sequence analysis showed that these genes belong to the superfamily of leucine-rich repeat (LRR) proteins. However, LRRs of this family display some variability in length and in amino acids composition within the beta-strands region, as more leucine residues are substituted by other hydrophobic amino acids as compared to canonical LRRs. Interestingly, for nine of these genes, the ESTs were represented almost exclusively in mouse egg libraries. Three of them were selected for experimental study. By RT-PCR and in situ hybridization, we confirmed their specific expression in the mouse oocyte from primary to preovulatory follicles. These three genes are localized in a cluster on mouse chromosome 4, in the vicinity of another recently discovered oocyte specific gene called oogenesin, that we also found to belong to the same family. We thus re-named this latter gene 'oogenesin-1', and the three genes identified here were named oogenesin-2, -3 and -4.