In the experiment shown below the authors Avella et al 2013

In the experiment shown below, the authors (Avella et al, 2013) generated several lines of transgenic mice. In each line, one mouse ZP glycoprotein was replaced by its human orthologue (the corresponding human ZP glycoprotein). So, in the eggs labeled HuZP1, mouse ZP1 has been replaced by human ZP1, etc. They then added human sperm to these eggs, to see whether the sperm could bind. 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). Human sperm bound only to the eggs containing human ZP2. The authors observed that the sperm bound to the eggs, penetrated the zona, and reached the space between the zona and the egg surface. However, the human sperm did not fertilize the mouse eggs. Based on this result, do you think that human Izumo1 (protein) can bind to mouse Juno (receptor)? Why or why not?

Solution

human Izumo1 protein can not bind to mouse juno receptor protein, because of

The Izumo is sperm specific protein, it’s essential for the sperm & egg plasma membrane first binding than fusion. Izumo is in mice produced morphologically same sperm that able to penetrated to zona pellucida, but it couldn’t fuse with to eggs. but In vitro human experiment conducted and they suggesting that the Izumo is required for the human gamete fusion. and by using the Western Blot analyse it has shown that the Izumo is expressed only in the testis & found on to the mature spermatozoa. so there is no way to bind to mouse zuno(receptor).

ZP(zona pellucida) is also species specific interaction, by experiment we modified in Zp glycoprotein so that the mouse ZP glycoprotein replace to human zp glycoprotein orthologus,and

so in the eggs labeled HuZP1, mouseZP1 has been replaced by human Zp1, than added human sperm to mouse eggs, to see sperm could bind or not, in this case sperm will bind to egg because of HuZp1 present on mouse egg so it’s recognized by human sperm and binding to zp of mice expressing human ZP2,Zp3 or huma ZP4.

only because of manipulation in receptore or it’s ligand, than it’s possible to interact but not to fuse with egg for fertilization, required more species specific receptore or ligand to fertilization ,

this experiment prove that fertilization is species specific receptore-ligand interaction is crucial for complete fertilization in any species.