Abstract
SPARC is a Mr 43,000 secreted, acidic, cysteine-rich glycoprotein homologous to 43K bovine endothelial 'culture shock' protein. We show here that it is encoded by a single gene localized to the central region of mouse chromosome 11. During development SPARC mRNA is expressed at higher levels in all the extra-embryonic tissues than in the fetus. Highest levels are found in the parietal endoderm, while visceral endoderm has approximately 6-fold less. This differential expression is also seen in F9 teratocarcinoma cells treated with retinoic acid under conditions in which they give rise to either parietal or visceral endoderm. The 20-fold increase seen during differentiation into parietal endoderm is due, at least in part, to an increase in gene transcription. We also report SPARC expression in a variety of adult tissues and cultured cells, and present evidence that a decrease accompanies the transformation of fibroblast cell lines.