Figure 2.

Human sperm bind to transgenic mice expressing human ZP2 in the ZP. Confocal and differential interference contrast images of capacitated human sperm binding to the ZP of mice expressing human ZP1, human ZP2, human ZP3 or human ZP4, in the absence of the corresponding mouse protein. Human oocytes and mouse eggs serve as positive and negative controls, respectively. Modified from ref. Baibakov et al. (2012).