Structure, chromosomal localization, and expression pattern of the murine Magp gene.

The microfibril-associated glycoprotein (MAGP) was recently established as a discrete constituent of 10-nm microfibrils. We have characterized the primary structure of the mouse transcript, the structure and chromosomal localization of the murine gene, and the developmental pattern of gene expression. The transcript consists of 1,037 base pairs as determined by cDNA cloning, Northern blot analysis, S1 nuclease mapping, and primer extension mapping. Using a cDNA fragment as a probe, we isolated a single genomic clone that contained the entire mouse gene. Analysis of this clone indicated that Magp is fragmented into 9 exons, with the initiator Met codon located in exon 2. As determined by analysis of somatic cell hybrid lines and by fluorescence in situ hybridization, the mouse gene was mapped to chromosome 4 at a location corresponding to region D3-E1. Genomic sequence immediately upstream of the transcription start site was found to be GC-rich but lacked TATA or CCAAT boxes as well as other cis-acting motifs known to regulate transcription. Promoters of this type are usually found in genes that exhibit broad temporal and spatial patterns of expression. Consistent with this idea, the Magp transcript appeared to be the widespread product of mesenchymal/connective tissue cells throughout mouse development. This study presents the first comprehensive evaluation of microfibril gene expression during mammalian development.