[5] Juno is a member of the folate receptor family[6] and is GPI-anchored to the plasmalemma of the mammalian egg cell that recognizes its sperm-riding counterpart, IZUMO1, and facilitates fertilization.

The protein was named after Juno, the Roman goddess of fertility and marriage.

[8] Mice lacking Juno on the surface of their egg cells are infertile because their egg cells do not fuse with normal sperm, demonstrating Juno's essential role in the fertility of female mice.

[6] In 2014, the function of folate receptor 4 was discovered by the researchers of the Wellcome Trust Sanger Institute who also proposed that the protein be renamed as Juno.

[7] The crystal structure of Juno (PDB: 5EJN​) was reported in February 2016 by researchers at Karolinska Institutet, in collaboration with the group at the Wellcome Trust Sanger Institute.