Alternative titles; symbols
HGNC Approved Gene Symbol: TRO
Cytogenetic location: Xp11.21 Genomic coordinates (GRCh38): X:54,920,824-54,931,431 (from NCBI)
The initial attachment of the trophoblast to the endometrial epithelium during implantation occurs via the apical cell membranes of the embryonic and maternal cells. Fukuda et al. (1995) found that cells from HT-H, a trophoblastic teratocarcinoma cell line, adhered efficiently to cells from SNG-M, an endometrial adenocarcinoma cell line. The adhesion was homophilic and cell type-specific, and occurred at the respective upper cell surfaces. To identify the adhesion molecules, the authors screened an HT-H expression library in COS-1 cells. They found that expression of 2 distinct cDNAs, encoding trophinin (cloned from trophoblastic cells) and tastin (603872), was necessary for adhesion. The deduced 749-amino acid trophinin protein contains 69 tandem repeats of decapeptide sequences. In vitro translated trophinin has a molecular mass of 61 kD. Sequence and structural analyses revealed that trophinin is an intrinsic plasma membrane protein with 8 predicted transmembrane domains, an intracellular N-terminal region, and 3 hydrophilic regions exposed on the cell surface. COS-1 cells expressing trophinin and tastin aggregated in suspension, and soluble peptides of the cell surface domain of trophinin bound to the cell surface of trophinin-expressing cells. Northern blot analysis detected trophinin expression as 3.5-, 7.5-, and 10-kb mRNAs in both HT-H and SNG-M cells. However, neither trophinin nor tastin was expressed in various other human cell types tested, with the exception of macrophages. Using immunofluorescence, Fukuda et al. (1995) detected strong expression of both genes in the trophectoderm surface of monkey blastocysts, as well as in human endometrial surface epithelium at a time consistent with that expected for the 'implantation window.' These authors suggested that trophinin and tastin might mediate the adhesion of the blastocyst to the endometrial epithelium at the time of implantation.
Using immunohistochemistry, Suzuki et al. (1999) determined that trophinin and bystin (603871), a trophinin- and tastin-binding protein, were found in the placenta from the sixth week of pregnancy. Trophinin and bystin were localized in the cytoplasm of the syncytiotrophoblast in the chorionic villi and in endometrial decidual cells at the uteroplacental interface. After week 10, the levels of trophinin, tastin, and bystin decreased and then disappeared from placental villi.
By fluorescence in situ hybridization, Pack et al. (1997) mapped the TRO gene to Xp11.22-p11.21.
Fukuda, M. N., Sato, T., Nakayama, J., Klier, G., Mikami, M., Aoki, D., Nozawa, S. Trophinin and tastin, a novel cell adhesion molecule complex with potential involvement in embryo implantation. Genes Dev. 9: 1199-1210, 1995. [PubMed: 7758945] [Full Text: https://doi.org/10.1101/gad.9.10.1199]
Pack, S. D., Tanigami, A., Ledbetter, D. H., Sato, T., Fukuda, M. N. Assignment of trophoblast/endometrial epithelium cell adhesion molecule trophinin gene TRO to human chromosome bands Xp11.22-p11.21 by in situ hybridization. Cytogenet. Cell Genet. 79: 123-124, 1997. [PubMed: 9533028] [Full Text: https://doi.org/10.1159/000134698]
Suzuki, N., Nakayama, J., Shih, I. M., Aoki, D., Nozawa, S., Fukuda, M. N. Expression of trophinin, tastin, and bystin by trophoblast and endometrial cells in human placenta. Biol. Reprod. 60: 621-627, 1999. [PubMed: 10026108] [Full Text: https://doi.org/10.1095/biolreprod60.3.621]