IZUMO1

Izumo sperm-egg fusion protein 1 (Sperm-specific protein izumo) is encoded in humans by the IZUMO1 gene.^[5] In mammalian fertilisation, IZUMO1 binds to its egg receptor counterpart, Juno, to facilitate recognition and fusion of the gametes. ^[6]

IZUMO1
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 5JKD, 5F4T, 5JKC, 5JK9, 5JKE, 5F4V, 5F4E
Identifiers
Aliases	IZUMO1, IZUMO, OBF, izumo sperm-egg fusion 1
External IDs	OMIM: 609278; MGI: 1920706; HomoloGene: 77701; GeneCards: IZUMO1; OMA:IZUMO1 - orthologs
Gene location (Human) Chr. Chromosome 19 (human)[1] Band 19q13.33 Start 48,740,852 bp[1] End 48,746,909 bp[1]
Gene location (Mouse) Chr. Chromosome 7 (mouse)[2] Band 7|7 B3 Start 45,621,811 bp[2] End 45,628,823 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right testis left testis sperm body of pancreas upper lobe of left lung right hemisphere of cerebellum body of stomach right adrenal cortex right lung apex of heart Top expressed in spermatid seminiferous tubule spermatocyte embryo blastocyst embryo yolk sac epiblast lip esophagus More reference expression data BioGPS n/a
Gene ontology Molecular function signaling receptor binding protein homodimerization activity protein binding identical protein binding protein binding involved in heterotypic cell-cell adhesion Cellular component membrane integral component of membrane plasma membrane acrosomal membrane cytoplasmic vesicle Biological process cell adhesion sperm-egg recognition single fertilization fusion of sperm to egg plasma membrane involved in single fertilization heterotypic cell-cell adhesion Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 284359 73456 Ensembl ENSG00000182264 ENSMUSG00000064158 UniProt Q8IYV9 Q9D9J7 RefSeq (mRNA) NM_182575 NM_001321864 NM_001321865 NM_001018013 RefSeq (protein) NP_001308793 NP_001308794 NP_872381 NP_001018013 Location (UCSC) Chr 19: 48.74 – 48.75 Mb Chr 7: 45.62 – 45.63 Mb PubMed search [3] [4]
Wikidata
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Function

The sperm-specific protein Izumo, named for a Japanese shrine dedicated to marriage, is essential for sperm-egg plasma membrane binding and fusion.^[7]

Studies have shown that male Izumo knockout mice are sterile because their sperm are unable to fuse to the oocyte membrane.[1] Izumo -/- mice produced morphologically normal sperm that were able to penetrate the zona pellucida, but could not fuse with to the eggs. In fact, it is necessary to relocate the IZUMO1 to the site of oocyte fusion.^[8] In-vitro human experiments have also been conducted, suggesting that Izumo is required for human gamete fusion. [1]

Through the use of Western Blot analyses, it has been shown that Izumo is only expressed in the testis and is found on mature spermatozoa. ^[9] Izumo-1 located on mature spermatozoa that have undergone capacitation binds to its receptor Juno, which is located on the oolemma of eggs. ^[10]