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HGNC Approved Gene Symbol: MFGE8
Cytogenetic location: 15q26.1 Genomic coordinates (GRCh38): 15:88,898,683-88,913,379 (from NCBI)
Stubbs et al. (1990) identified a cDNA for a mouse mammary epithelial cell surface protein, which they called milk fat globule-EGF factor 8 (MFGE8) because of its regions of sequence similarity to epidermal growth factor (EGF) and blood clotting factors VIII (300841) and V (612309). Larocca et al. (1991) raised monoclonal antibodies to a 46-kD human milk fat globule protein, later to be identified as the human homolog of MFGE8, and isolated a partial cDNA by immunoscreening a lambda gt11 human breast cDNA library. Collins et al. (1997) cloned the MFGE8 gene from a human infant cDNA brain library. The gene predicts a protein of 387 amino acids of which 263 (68%) are identical or conserved matches with the mouse protein.
Taylor et al. (1997) stated that human lactadherin has 3 domains: an EGF-like domain, which contains an arg-gly-asp (RGD) cell adhesion sequence, and C1 and C2 domains similar to those found in coagulation factors V and VIII. Western blot analysis of lactadherin purified from human milk detected a 46-kD protein.
By affinity chromatography with immobilized porcine zona pellucida glycoproteins, Ensslin et al. (1998) purified Spag10, which they designated P47, from porcine spermatozoa. They designed degenerate primers to clone SPAG10 by PCR of a human testis cDNA library and other mammalian cDNA libraries. Northern blot analysis revealed a 2.0-kb transcript expressed in human testis and in several porcine and bovine tissues. Western blot analysis detected SPAG10 in porcine and human milk.
Hanayama et al. (2004) demonstrated that 'tingible body' macrophages in the germinal centers of the spleen and lymph nodes strongly express MFGE8.
Ensslin and Shur (2003) cloned mouse Mfge8, which they called Sed1, from a testis cDNA library. Sed1 localized to the Golgi complex of differentiating spermatogenic cells. It was secreted by the initial segment of the caput epididymis and adhered to the sperm plasma membrane overlying the acrosome.
Using RT-PCR, Silvestre et al. (2005) detected expression of mouse Mfge8 in aorta and hindlimb muscle. Western blot analysis of mouse aorta and dendritic cells revealed bands of about 64 and 56 kD. Immunohistochemical analysis of human arteries showed MFGE8 mainly in adventitial microvessels, medial smooth muscle cells, and some luminal endothelial cells.
Medin
Aortic medial amyloid is a form of localized amyloid that occurs in virtually all individuals older than 60 years. Haggqvist et al. (1999) purified a 5.5-kD aortic medial amyloid component by size-exclusion chromatography and reversed phase-HPLC from 3 individuals, and showed by amino acid sequence analysis that the amyloid is derived from an integral proteolytic fragment of lactadherin. Lactadherin is a 364-amino acid glycoprotein known to be expressed by mammary epithelial cells as a cell surface protein and secreted as part of the milk fat globule membrane (Larocca et al., 1991; Aoki et al., 1997). The multidomain protein has a C-terminal domain showing homology to blood coagulation factors V and VIII. They found that the main constituent of aortic medial amyloid is a 50 amino acid-long peptide, designated medin by Haggqvist et al. (1999), that is positioned within the coagulation factor-like domain of lactadherin. This result was supported by the specific labeling of aortic medial amyloid in light and electron microscopy with 2 rabbit antisera raised against 2 synthetic peptides corresponding to different parts of medin. Using in situ hybridization, they showed that lactadherin is expressed by aortic medial smooth muscle cells. Furthermore, one of the synthetic peptides formed amyloid-like fibrils in vitro. Lactadherin had not been known to be an amyloid precursor protein or to be expressed in aortic tissue. Homology of lactadherin with other proteins implicated its involvement in important cell surface-mediated regulatory events.
Taylor et al. (1997) found that purified human lactadherin promoted cell attachment in several mammalian cell lines, including human mammary carcinoma cells. Attachment was inhibited by addition of an RGD peptide or antibodies specific to lactadherin. Anti-integrin alpha-V (ITGAV; 193210)-beta-3 (ITGB3; 173470) inhibited attachment of green monkey cells to lactadherin. Taylor et al. (1997) concluded that lactadherin promotes RGD-dependent cell adhesion via integrins.
Hanayama et al. (2002) found that MFGE8 is a factor that links apoptotic cells to phagocytes. MFGE8 specifically bound to apoptotic cells by recognizing aminophospholipids such as phosphatidylserine. MFGE8, when engaged by phospholipids, bound to cells via its RGD motif. It bound particularly strongly to cells expressing alpha-V-beta-3 integrin. The NIH 3T3 cell transformants that expressed a high level of alpha-V-beta-3 integrin engulfed apoptotic cells when MFGE8 was added. MFGE8 carrying a point mutation in the RGD motif behaved as a dominant-negative form, and inhibited the phagocytosis of apoptotic cells by peritoneal macrophages in vitro and in vivo. Hanayama et al. (2002) concluded that MFGE8 secreted from activated macrophages binds to apoptotic cells and brings them to phagocytes for engulfment.
Ensslin and Shur (2003) found that mouse Sed1 bound to the zona pellucida of unfertilized oocytes, but not to the zona of fertilized eggs. Recombinant Sed1 and anti-Sed1 antibodies competitively inhibited sperm-egg binding, as did truncated Sed1 proteins containing the discoidin/C domain.
Using neutralizing antibodies and lactadherin-deficient mice, Silvestre et al. (2005) showed that lactadherin interacted with alpha-V-beta-3 and alpha-V-beta-5 (ITGB5; 147561) integrins and altered Vegf (192240)-dependent Akt (see 164730) phosphorylation and neovascularization. In the absence of Vegf, lactadherin administration induced alpha-V-beta-3- and alpha-V-beta-5-dependent Akt phosphorylation in endothelial cells in vitro and improved postischemic neovascularization in vivo. Silvestre et al. (2005) concluded that lactadherin modulates VEGF-dependent neovascularization.
Bu et al. (2007) showed that Mfge8 was expressed in intestinal lamina propria macrophages in mice. Using a wound-healing assay, they showed that Mfge8 promoted migration of intestinal epithelial cells through a PKC-epsilon (PRKCE; 176975)-dependent mechanism. Mfge8 bound to phosphatidylserine and triggered reorientation of the actin cytoskeleton in intestinal epithelial cells at the wound edge. Depletion of Mfge8 in mice by anti-Mfge8 antibody or targeted deletion of the Mfge8 gene resulted in a slowing of enterocyte migration along the crypt-villus axis and focal mucosal injury. In septic mice, intestinal Mfge8 expression was downregulated, which correlated with intestinal injury, interrupted enterocyte migration, and impaired restitution. Treatment with recombinant Mfge8 restored enterocyte migration, whereas deletion of Mfge8 impeded mucosal healing in mice with sepsis. Bu et al. (2007) concluded that MFGE8 plays a role in maintenance of intestinal epithelial homeostasis and promotion of mucosal healing.
By fluorescence in situ hybridization, Collins et al. (1997) mapped the MFGE8 gene to chromosome 15q25.
Ensslin and Shur (2003) found that Sed1-null male mice were subfertile. Sperm from Sed1-null mice were unable to bind to the egg coat in vitro.
Hanayama et al. (2004) generated mice deficient in Mfge8 by targeted disruption. Many apoptotic lymphocytes were found on tingible body macrophages from mutant mice, but they were not efficiently engulfed. Mfge8-null mice developed splenomegaly, with formation of numerous germinal centers, and suffered from glomerulonephritis as a result of antibody production. Hanayama et al. (2004) concluded that their data demonstrated that MFGE8 has a critical role in removing apoptotic B cells in the germinal centers and that its failure can lead to autoimmune diseases.
Hanayama and Nagata (2005) found that deficiency of Mfge8 caused the accumulation of milk fat globules in mammary ducts during involution. Mfge8-null mice developed mammary duct ectasia with periductal mastitis, and redevelopment of the mammary gland for a second litter was impaired. The authors concluded that MFGE8-mediated phagocytosis of apoptotic epithelial cells and milk fat globules is important for efficient involution of mammary glands.
Ensslin and Shur (2007) found that mammary glands of Mfge8-null mice showed reduced branching from epithelial ducts and from terminal end buds, which were thin and poorly developed. Mfge8 was expressed in both luminal and myoepithelial cells in the developing epithelial duct, and Mfge8 bound alpha-5 integrin receptors on myoepithelial cells leading to Mapk (see MAPK1, 176948) activation and cell proliferation. Absence of Mfge8 led to reduced activation of Mapk and a concomitant reduction in cell proliferation and branching.
Aoki, N., Ishii, T., Ohira, S., Yamaguchi, Y., Negi, M., Adachi, T., Nakamura, R., Matsuda, T. Stage specific expression of milk fat globule membrane glycoproteins in mouse mammary gland: comparison of MFG-E8, butyrophilin, and CD36 with a major milk protein, beta-casein. Biochim. Biophys. Acta 1334: 182-190, 1997. [PubMed: 9101712] [Full Text: https://doi.org/10.1016/s0304-4165(96)00091-8]
Bu, H.-F., Zuo, X.-L., Wang, X., Ensslin, M. A., Koti, V., Hsueh, W., Raymond, A. S., Shur, B. D., Tan, X.-D. Milk fat globule-EGF factor 8/lactadherin plays a crucial role in maintenance and repair of murine intestinal epithelium. J. Clin. Invest. 117: 3673-3683, 2007. [PubMed: 18008006] [Full Text: https://doi.org/10.1172/JCI31841]
Collins, C., Nehlin, J. O., Stubbs, J. D., Kowbel, D., Kuo, W.-L., Parry, G. Mapping of a newly discovered human gene homologous to the apoptosis associated-murine mammary protein, MFG-E8, to chromosome 15q25. Genomics 39: 117-118, 1997. [PubMed: 9027496] [Full Text: https://doi.org/10.1006/geno.1996.4425]
Ensslin, M. A., Shur, B. D. Identification of mouse sperm SED1, a bimotif EGF repeat and discoidin-domain protein involved in sperm-egg binding. Cell 114: 405-417, 2003. [PubMed: 12941270] [Full Text: https://doi.org/10.1016/s0092-8674(03)00643-3]
Ensslin, M. A., Shur, B. D. The EGF repeat and discoidin domain protein, SED1/MFG-E8, is required for mammary gland branching morphogenesis. Proc. Nat. Acad. Sci. 104: 2715-2720, 2007. [PubMed: 17299048] [Full Text: https://doi.org/10.1073/pnas.0610296104]
Ensslin, M., Vogel, T., Calvete, J. J., Thole, H. H., Schmidtke, J., Matsuda, T., Topfer-Petersen, E. Molecular cloning and characterization of P47, a novel boar sperm-associated zona pellucida-binding protein homologous to a family of mammalian secretory proteins. Biol. Reprod. 58: 1057-1064, 1998. [PubMed: 9546740] [Full Text: https://doi.org/10.1095/biolreprod58.4.1057]
Haggqvist, B., Naslund, J., Sletten, K., Westermark, G. T., Mucchiano, G., Tjernberg, L. O., Nordstedt, C., Engstrom, U., Westermark, P. Medin: an integral fragment of aortic smooth muscle cell-produced lactadherin forms the most common human amyloid. Proc. Nat. Acad. Sci. 96: 8669-8674, 1999. [PubMed: 10411933] [Full Text: https://doi.org/10.1073/pnas.96.15.8669]
Hanayama, R., Nagata, S. Impaired involution of mammary glands in the absence of milk fat globule EGF factor 8. Proc. Nat. Acad. Sci. 102: 16886-16891, 2005. [PubMed: 16275924] [Full Text: https://doi.org/10.1073/pnas.0508599102]
Hanayama, R., Tanaka, M., Miwa, K., Shinohara, A., Iwamatsu, A., Nagata, S. Identification of a factor that links apoptotic cells to phagocytes. Nature 417: 182-187, 2002. [PubMed: 12000961] [Full Text: https://doi.org/10.1038/417182a]
Hanayama, R., Tanaka, M., Miyasaka, K., Aozasa, K., Koike, M., Uchiyama, Y., Nagata, S. Autoimmune disease and impaired uptake of apoptotic cells in MFG-E8-deficient mice. Science 304: 1147-1150, 2004. [PubMed: 15155946] [Full Text: https://doi.org/10.1126/science.1094359]
Larocca, D., Peterson, J. A., Urrea, R., Kuniyoshi, J., Bistrain, A. M., Ceriani, R. L. A M(r) 46,000 human milk fat globule protein that is highly expressed in human breast tumors contains factor VIII-like domains. Cancer Res. 51: 4994-4998, 1991. [PubMed: 1909932]
Silvestre, J.-S., Thery, C., Hamard, G., Boddaert, J., Aguilar, B., Delcayre, A., Houbron, C., Tamarat, R., Blanc-Brude, O., Heeneman, S., Clergue, M., Duriez, M., Merval, R., Levy, B., Tedgui, A., Amigorena, S., Mallat, Z. Lactadherin promotes VEGF-dependent neovascularization. Nature Med. 11: 499-506, 2005. [PubMed: 15834428] [Full Text: https://doi.org/10.1038/nm1233]
Stubbs, J. D., Lekutis, C., Singer, K. L., Bui, A., Yuzuki, D., Srinivasan, U., Parry, G. cDNA cloning of a mouse mammary epithelial cell surface protein reveals the existence of epidermal growth factor-like domains linked to factor VIII-like sequences. Proc. Nat. Acad. Sci. 87: 8417-8421, 1990. [PubMed: 2122462] [Full Text: https://doi.org/10.1073/pnas.87.21.8417]
Taylor, M. R., Couto, J. R., Scallan, C. D., Ceriani, R. L., Peterson, J. A. Lactadherin (formerly BA46), a membrane-associated glycoprotein expressed in human milk and breast carcinomas, promotes Arg-Gly-Asp (RGD)-dependent cell adhesion. DNA Cell Biol. 16: 861-869, 1997. [PubMed: 9260929] [Full Text: https://doi.org/10.1089/dna.1997.16.861]