We report here the full coding sequence of a novel mouse putative membrane-associated mucin containing three extracellular EGF-like motifs and a mucin-like domain consisting of at least 20 tandem repeats of 124–126 amino acids. Screening a cosmid and a BAC libraries allowed to isolate several genomic clones. Genomic and cDNA sequence comparisons showed that the gene consists of 25 exons and 24 introns covering a genomic region of 52 kb. The first intron is 16 kb in length and is followed by an unusually large exon ( kb) encoding Ser/Thr-rich tandemly repeated sequences