Revised genomic structure of the human MAGP1 gene and identification of alternate transcripts in human and mouse tissues

The human MAGP1 (or MFAP2) and mouse Magp1 genes code for the microfibril-a ssociated glycoprotein-1 (MAGP-1), an extracellular matrix protein of micro fibrillar structures. We report a revised 5' genomic structure including th e use of a single transcription start site that gives rise to a 32-bp 5' ex on spanning a segment of the previously described exon B. No evidence of he terogeneous 5' ends from the use of alternative promoters was found in huma n tissues and cell lines. We located the genetic marker D1S170 to a positio n 3 kb downstream of the polyadenylation site. Large-scale comparison of th e human and mouse genes revealed conservation of sequence outside the codin g exons. Although the 5' flanking regions were found to be divergent certai n cis-elements for transcription factors are conserved, including Sp1, AP-2 , AP-4, NF-kappaB, and c-ETS motifs. We identified a total of five splice v ariants in addition to the canonical MAGP1A/Magp1A form. These transcripts are species-specific and are generated by different processing mechanisms. The alternate forms MAGP1A', MAGP1B, and MAGP1C are expressed in human tiss ues; and the two variants Magp1A" and Magp1D were found only in mouse. The alternatively spliced forms show restricted patterns of expression relative to the canonical isoform. (C) 2000 Elsevier Science B.V./International Soc iety of Matrix Biology. All rights reserved.