Genomic organization of a sex specific gene: the primary sperm receptor of the mouse zona pellucida.

The zona pellucida is an extracellular matrix which surrounds mammalian oocytes and plays an important role in the species-specific fertilization of mammals. The mouse zona is composed of three sulfated glycoproteins one of which, ZP3, serves as the primary sperm receptor in the initial interaction between egg and sperm. We have previously cloned a ZP3 cDNA and shown that the gene for ZP3 is expressed in a precise temporal and spatial fashion only in growing oocytes. We now describe the genomic organization of this gene whose expression is germ-line and female sex-specific. The gene contains 8 exons spanning approximately 8.6 kilobases in the mouse genome where it appears to be present as a single copy gene. S1 analyses of the 5' and 3' ends of the gene define the transcription start and stop sites and show that ZP3 mRNA has very short untranslated regions. Sequence determination has revealed a novel tandem repeat which is reiterated six times in the 5' flanking region and five times in the seventh intron.