CLONING, CHARACTERIZATION, AND TISSUE EXPRESSION PATTERN OF MOUSE TUFTELIN CDNA

Tuftelin is a protein that has been suggested to function during ename l crystal nucleation. Published sequences for bovine tuftelin cDNA and genomic clones proposed different reading frames that radically affec ted the derived amino acid sequence of the tuftelin carboxyl-terminus. We have isolated and characterized a full-length mouse cDNA clone and a partial porcine cDNA clone that include the region of the proposed frame-shift. The mouse tuftelin clone is 2572 nucleotides in length, e xclusive of the poly(A+) tail. Translation from the 5'-most ATG yields a protein of 390 amino acids with an isotope-averaged molecular mass of 44.6 kDa and an isoelectric point of 5.9. Comparison of the bovine, mouse, and porcine cDNAs supports the revised bovine tuftelin amino a cid sequence and suggests that the bovine tuftelin translation initiat ion codon be re-assigned to a more 5' ATG. Re-assigning the translatio n initiation codon lengthens the tuftelin protein by 52 amino acids, 5 1 of which are identical between bovine and mouse. At the carboxyl-ter minus, the revised bovine and the mouse sequences match at 39 of the f inal 42 amino acid positions, compared with 2 identities with the orig inally published bovine reading frame. Northern blot analysis reveals that tuftelin is not ameloblast-specific but is expressed in multiple tissues, including kidney, lung, Liver, and testis. Two tuftelin RNA m essages, of 2.6 and 3.2 kb, were detected. DNA sequence characterizati on of an RT-PCR amplification product confirmed expression of tuftelin in kidney, and identified an alternatively spliced mouse tuftelin mRN A lacking exon 2.