File:Human zona proteins in transgenic mouse oocyte 01.jpg

Human zona proteins incorporated into transgenic mouse oocyte zona pellucida

Ovulated eggs from human ZP1 (huZP1), huZP2, and huZP3 rescue as well as huZP4 transgenic mice were fixed and stained with mAb to human ZP1 (huZP1), huZP2, huZP3, huZP4, mouse ZP1 (moZP1), moZP2, and moZP3. Antibody binding to human and mouse zona proteins was detected by confocal microscopy and faux colored dark blue (huZP1), red (huZP2), green (huZP3), orange (huZP4), magenta (moZP1), light blue (moZP2), or yellow (moZP3). Fluorescent and DIC images were merged.

Figure 1. http://jcb.rupress.org/content/197/7/897/F1.expansion.html

Human sperm bind to the N-terminal domain of ZP2 in humanized zonae pellucidae in transgenic mice.

J Cell Biol. 2012 Jun 25;197(7):897-905. doi: 10.1083/jcb.201203062.

Baibakov B1, Boggs NA, Yauger B, Baibakov G, Dean J.

Abstract Fertilization requires taxon-specific gamete recognition, and human sperm do not bind to zonae pellucidae (ZP1-3) surrounding mouse eggs. Using transgenesis to replace endogenous mouse proteins with human homologues, gain-of-function sperm-binding assays were established to evaluate human gamete recognition. Human sperm bound only to zonae pellucidae containing human ZP2, either alone or coexpressed with other human zona proteins. Binding to the humanized matrix was a dominant effect that resulted in human sperm penetration of the zona pellucida and accumulation in the perivitelline space, where they were unable to fuse with mouse eggs. Using recombinant peptides, the site of gamete recognition was located to a defined domain in the N terminus of ZP2. These results provide experimental evidence for the role of ZP2 in mediating sperm binding to the zona pellucida and support a model in which human sperm-egg recognition is dependent on an N-terminal domain of ZP2, which is degraded after fertilization to provide a definitive block to polyspermy.

PMID 22734000

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