juno (protein) juno (protein) juno also known as folate receptor 4, folate receptor delta or izumo1r is a protein that in humans is encoded by the folr4 gene. juno is a member of the folate receptor family 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. izumo1ravailable structurespdbortholog search: pdbe rcsb list of pdb id codes5jkd, 5f4q, 5jkb, 5f4e, 5jka, 5jkc, 5jkeidentifiersaliasesizumo1r, folbp3, juno, folr4, juno (protein), izumo1 receptor, juno, fr-deltaexternal idsomim: 615737 mgi: 1929185 homologene: 11283 genecards: izumo1r gene location (human)chr.chromosome 11 (human)band11q21start94,304,580 bpend94,308,146 bpgene location (mouse)chr.chromosome 9 (mouse)band9|9 a2start14,797,110 bpend14,815,245 bprna expression patternbgeehumanmouse (ortholog)top expressed inlymph nodeascending aortasural nerveachilles tendonleft coronary arteryright coronary arterysmooth muscle tissueappendixrectumpopliteal arterytop expressed insecondary oocytethymusmorulaspleenbloodjejunumovaryyolk sacblastocystmuscular systemmore reference expression databiogpsn/agene ontologymolecular function protein binding folic acid binding signaling receptor activity signaling receptor binding cellular component anchored component of membrane membrane extracellular region plasma membrane anchored component of external side of plasma membrane biological process single fertilization cell adhesion fusion of sperm to egg plasma membrane involved in single fertilization sperm-egg recognition signal transduction sources:amigo / quickgoorthologsspecieshumanmouseentrez39024364931ensemblensg00000183560ensmusg00000031933uniprota6nd01q9eqf4refseq (mrna)nm_001080486nm_001199206nm_001393610nm_022888nm_176807refseq (protein)np_001186135np_075026np_789777location (ucsc)chr 11: 94.3 – 94.31 mbchr 9: 14.8 – 14.82 mbpubmed searchwikidataview/edit humanview/edit mouse 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 intracytoplasmic sperm injection, the egg cell does not lose cell-surface expression of juno, which suggests that juno contributes to the prevention of polyspermy. 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. discovery based on a sequence homology search for genes relate to the folate receptor, the gene for folate receptor 4 was first identified in mice and humans in 2000 at the university of nebraska. 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. juno was initially found in murine 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. 3d structure 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. model organisms model organisms have been used in the study of juno function. a conditional knockout mouse line called izumo1rtm2a(komp)wtsi was generated at the wellcome trust sanger institute. male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. additional screens performed: - in-depth immunological phenotyping izumo1r knockout mouse phenotype characteristicphenotype all data available at. peripheral blood leukocytes 6 weeksnormal haematology 6 weeksnormal insulinnormal homozygous viability at p14normal homozygous fertilityabnormal body weightnormal neurological assessmentnormal grip strengthnormal dysmorphologynormal indirect calorimetrynormal glucose tolerance testnormal auditory brainstem responsenormal dexanormal radiographynormal eye morphologynormal clinical chemistrynormal haematology 16 weeksnormal peripheral blood leukocytes 16 weeksnormal heart weightnormal salmonella infectionnormal cytotoxic t cell functionnormal spleen immunophenotypingnormal mesenteric lymph node immunophenotypingnormal bone marrow immunophenotypingnormal epidermal immune compositionnormal trichuris challengenormal