4/24/2023 0 Comments Corona radiataNo zona-free 2-cell embryos were recovered from homozygous mutant Zp3-/- female mice after mating with males proven to be fertile, and none became visibly pregnant or produced offspring. After hormone-induced ovulation, cumulus masses were present in the oviducts of homozygous mutant mice, but zona-free eggs were observed in only half of the females and, in these, less than 10% of the normal number of eggs were detected. Although mutant oocytes underwent germinal vesicle breakdown (GVBD) prior to ovulation, the cumulus-oocyte complex was markedly disrupted and the oocytes were often separate from the cumulus cells. Homozygous mutant Zp3-/- mice had follicles with germinal-vesicle-intact oocytes but that lacked a zona pellucida matrix and had a disorganized corona radiata. Neither Zp3 transcripts nor ZP3 protein was detected in female mice homozygous for the mutation (Zp3-/-), whereas both ZP1 and ZP2 were present in mutant oocytes. We have established a mouse line in which Zp3 has been inactivated by homologous recombination with an insertional mutation. The extracellular zona matrix is composed of three glycoproteins (ZP1, ZP2, ZP3) that are involved in folliculogenesis, species-specific fertilization, and passage of the early embryo down the oviduct. Abstract: Mammalian oocytes synthesize and secrete a zona pellucida that surrounds the growing oocytes, ovulated eggs and preimplantation embryos.
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