THE MURINE BIGLYCAN - COMPLETE CDNA CLONING, GENOMIC ORGANIZATION, PROMOTER FUNCTION, AND EXPRESSION

Biglycan is a ubiquitous chondroitin/dermatan sulfate proteoglycan tha t belongs to a growing family of proteins harboring leucine-rich repea ts. We have cloned and sequenced the cDNA containing the complete muri ne biglycan, elucidated its genomic organization, and demonstrated fun ctional promoter activity of its 5' flanking region. The deduced bigly can protein core was highly conserved across species. However, the mou se biglycan (Bgn) gene was significantly larger than the human counter part, primarily because of a large >4.5-kb intron between exons 1 and 2. The mouse Bgn gene spanned over 9.5 kb of continuous DNA and compri sed 8 exons, with a perfectly conserved intron/exon organization vis-a -vis the human counterpart, The promoter region was enriched in GC din ucleotide and contained numerous cts-acting elements including binding sites for SP-1, AP-1, and AP-2 factors, It lacked TATA and CAAT boxes typical of housekeeping genes. In support of this, primer extension a nalysis showed the existence of multiple transcription start sites. Tr ansient cell transfection assays with a construct comprising the 548 b p upstream of the major transcription start site fused to the chloramp henicol acetyl transferase reporter gene showed functional promoter ac tivity, Internal and 5' deletion constructs showed that the distal pro moter of the Bgn gene was required for full transcriptional activity, In contrast to the homologous proteoglycan decorin, the highest expres sion of biglycan mRNA was observed in lung, liver, and spleen of adult mouse and the lowest in skin, heart, and kidney. These results will b e useful for the study of biglycan gene regulation and for the generat ion of mice with targeted null mutation of the Bgn gene. (C) 1995 Acad emic Press, Inc.