STRUCTURAL-ANALYSIS OF MOUSE TENASCIN-X - EVOLUTIONARY ASPECTS OF REDUPLICATION OF FNIII REPEATS IN THE TENASCIN GENE FAMILY

Tenascin-X (TNX) is an extracellular matrix glycoprotein involved in b oth primary structural functions and modulating cellular activities in multicellular organisms. We determined the 67977 bp nucleotide sequen ce of the entire mouse tenascin-X (Tnx) gene, which also includes the last exon of Cr eb-rp and Cyp21. We compared it with the orthologous h uman locus. Conservation of both position and orientation of the three functionally unrelated genes at this position was found. Comparison a lso revealed that introns 1, 4 and 6 of Tnx are highly conserved betwe en species. The sequence showed that mouse Tnx contains 43 exons separ ated by 42 introns. The deduced amino-acid sequence (4114 residues) re vealed that mouse Tnx has a primary structure characteristic of tenasc ins, which consists of a signal peptide and four heptad repeats follow ed by 18.5 epidermal growth factor-like (EGF) repeats, 31 fibronectin type III-like (FNIII) repeats, and a region homologous to fibrinogen. cDNA clones generated by alternative splicing of eight consecutive FNI II repeats (M15-M22) as well as a proximal FNIII repeat (M3) were also identified. The FNIII motifs that were subject to alternative splicin g were assigned to the group of recently reduplicated FNIII repeats be cause they have a high level of amino-acid sequence similarity. We als o analyzed the evolution of FNIII repeats in TNX. (C) 1998 Elsevier Sc ience B.V. All rights reserved.