Juno (protein)

Juno also known as folate receptor 4, folate receptor delta or IZUMO1R is a is_associated_with::protein that in humans is encoded by the FOLR4 is_associated_with::gene. Juno is a member of the is_associated_with::folate receptor family and is located on the surface of the mammalian is_associated_with::egg cell that recognizes its is_associated_with::sperm-riding counterpart, is_associated_with::IZUMO1, and facilitates is_associated_with::fertilization. The protein was named after Juno, the Roman goddess of fertility and marriage.

After the initial fertilisation stage, a sudden decrease of Juno from the egg cell surface occurs and Juno becomes virtually undetectable after just 40 minutes. Still, after fertilization via is_associated_with::intracytoplasmic sperm injection, the egg cell does not lose cell-surface expression of Juno, which suggests that Juno contributes to the prevention of is_associated_with::polyspermy. Mice lacking Juno on the surface of their egg cells are is_associated_with::infertile because their egg cells do not fuse with normal sperm, demonstrating Juno's essential role in the fertility of female mice.

Discovery
Based on a sequence homology search for genes relate to the is_associated_with::folate receptor, the gene for folate receptor 4 was first identified in mice and humans in 2000 at the is_associated_with::University of Nebraska.

In 2014, the function of folate receptor 4 was discovered by the researchers of the is_associated_with::Wellcome Trust Sanger Institute who also proposed that the protein be renamed as Juno. Juno was initially found in murine is_associated_with::oocytes, but its interaction with Izumo was subsequently found in other mammalian species, including humans. Being previously elusive, Juno was discovered nine years after its male counterpart, Izumo1.

Model organisms
is_associated_with::Model organisms have been used in the study of JUNO function. A conditional is_associated_with::knockout mouse line called Izumo1rtm2a(KOMP)Wtsi was generated at the is_associated_with::Wellcome Trust Sanger Institute. Male and female animals underwent a standardized is_associated_with::phenotypic screen to determine the effects of deletion. Additional screens performed: - In-depth immunological phenotyping

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