Human tenascin-C: Identification of a novel type III repeat in oral cancer and of novel splice variants in normal, malignant and reactive oral mucosae

Abstract

Tenascin-C is a mosaic, linear glycoprotein that is upregulated during many normal and pathological processes involving either cell migration or tissue morphogenesis, such as invasion of malignant cells and wound healing. Human tenascin-C contains 8 consecutive type III fibronectin (TNCfn) domains that are involved in alternative splicing and potentially generate a large number of isoforms that code for tenascin-C proteins with subtly different functions. Human tenascin-C splice variants were investigated by RT-PCR in a range of normal and pathological oral mucosal tissues. A novel, 9th human TNCfn domain involved in alternative splicing was identified. It shares 70% nucleic acid and 55% protein sequence homology with chicken TNCfn-ad2. As in avians, this novel repeat was located between TNCfn-B and TNCfn-ad1 and accordingly was designated human TNCfnad2. Human TNCfn-ad2 was detected in only 2 of 10 oral cancers. However, TNCfn-ad2 was absent from 40 normal, reactive, pre-malignant and other oral mucosal specimens investigated. Previous studies have described 8 splice variant transcripts for human tenascin-C. By systematic investigation we identified further novel splice variants for human tenascin-C. Furthermore, our results indicate that many potential splice variants probably do not exist in the tissues investigated. Thus, we have demonstrated that human tenascin-C transcripts generate a complex but selected repertoire of different alternative splice products. Int.

Tenascin-C: Form versus function

“…However, 2 further alternatively spliced FNIII domains (additional domains 1 and 2: FNIII AD1 27 and AD2 28 (accession numbers U88892.1 and EU295718.1 respectively) were later discovered. FNIII AD1 was identified within human U251 glioma cDNA clones as a single exon between FNIII repeats B and C. This study also showed that while AD1 was present in human glioblastoma, neuroblastoma and osteosarcoma tumor cells, it was absent in healthy human lung fibroblasts and umbilical vein endothelial cells (HUVECs) providing the first indication that tenascin-C splicing may play a role in tumorigenesis.…”

“…27 Human FNIII AD2 was discovered between FNIII B and AD1 in oral mucosa carcinoma samples and was named so on account of being in the same respective location as the avian FNIII AD2; situated between FNII B and AD1, in addition to it sharing 70% amino acid and 55% nucleotide sequence homology with the avian FNIII AD2. 28,29 Thus human TNC contains 30 exons (Fig. 1).…”

“…However, the number of alternatively spliced FNIII repeats varies by species; with chickens and mice, rats, and humans having 6, 7 and 9 respectively. 28,31,32 Theoretically there are 511 possible human tenascin-C splice isoforms; this figure was calculated via the equation 9! 9 ¡ r ð Þ!…”

Involvement of Large Tenascin-C Splice Variants in Breast Cancer Progression

“…30 Transcripts for splice variants including the AD2 repeat are found in oral cancer tissues, but not in normal and pre-malignant tissues. 31 Immunohistochemistry using a recombinant antibody to the spliced repeat C has shown that the repeat is not detectable in normal adult tissues, not or barely detectable in malignant epithelial tumors, but abundant in glioblastomas. 32 From quantitative analysis using antibodies against alternative spliced domains, an increased fraction of Tn-C containing A1-A4 appears related to the tumor stage of colorectal cancer, while domain D is down-regulated in metastasizing cancers.…”

Extracellular Matrix of Glioblastoma Inhibits Polarization and Transmigration of T Cells: The Role of Tenascin-C in Immune Suppression

“…Reverse transcription was performed at 37˚C for 60 min in a 20-ml reaction containing 2 mg RNA, 500 ng oligo(dT) primers, 4 ml 53 RT buffer (250 mM Tris-HCl [pH 8.3], 375 mM KCl, 15 mM MgCl 2 , and 50 mM DTT), 0.5 ml of 40 mM 29-deoxynucleoside 59-triphosphate, 0.5 ml of 200 U/ml RNase inhibitor (Promega, Madison, WI), 3.5 ml diethyl pyrocarbonate-treated water, and 1 ml of 200 U/ml M-MLV reverse transcriptase (Promega, Madison, WI). The oligonucleotide primers used are listed in Table I ( [23][24][25][26]. PCR cycles were carried out on a DNA thermal cycler (Hybaid Omnigene, Middlesex, U.K.).…”