Cloning and Expression of Murine SC1, a Gene Product Homologous to SPARC

Abstract

SUMMARY A number of cDNAs (SC1, QR1, and hevin) have been shown to be similar to SPARC (secreted protein acidic and rich in cysteine), a matricellular protein that regulates cell adhesion, cell cycle, and matrix assembly and remodeling. These proteins are 61-65% identical in the final 200 residues of their C-termini; their N-terminal sequences are related but more divergent. All have an overall acidic pI, with a follistatin-like region that is rich in cysteine, and a Ca ϩ2 binding consensus sequence at the C-terminus. Using degenerate primers representing the most highly conserved region in SPARC, SC1, and QR1, we identified a 300-BP SC1 clone in a primary polymerase chain reaction (PCR) screen of a mouse brain cDNA library. This cDNA was used to obtain a full-length clone, which hybridized to a 2.8-KB RNA abundant in brain. Mouse SC1 displays a similarity of 70% to mouse SPARC at the amino acid level. Northern blot and RNAse protection assays revealed a 2.8-KB mRNA expressed at moderate levels (relative to brain) in mouse heart, adrenal gland, epididymis, and lung, and at low levels in kidney, eye, liver, spleen, submandibular gland, and testis. In contrast to SPARC, in situ hybridization showed expression of SC1 mRNA in the tunica media and/or adventitia of medium and large vessels; transcripts were not detected in capillaries, venules, or large lymphatics. The distribution of transcripts for SC1 was also different from that of SPARC in several organs, including adrenal gland, lung, heart, liver, and spleen. Moreover, SC1 mRNA was not evident in endothelium cultured from rat heart, bovine fetal and adult aorta, mouse aorta, human omentum, and bovine retina. Cultured smooth muscle cells and fibroblasts also failed to express SC1 mRNA. The absence of SC1 transcript in cultured cells indicates that the SC1 gene is potentially sensitive to regulatory factors in serum or to a three-dimensional architecture conferred by the extracellular matrix that is lacking in vitro. In conclusion, the expression of SPARC and SC1 appears to be coincident in specific tissues (e.g., adrenal gland and brain), but these proteins exhibit distinct expression patterns in most organs of the mouse. Because SC1 and SPARC are structurally similar and exhibit counteradhesive effects on cultured cells, their overlapping and/or adjacent expression in most tissues predicts that one protein might compensate functionally, at least in part, for the other. The sequence reported here has been deposited in the GenBank data base (accession no. U77330). (J Histochem Cytochem 45:823-835, 1997)

Expression and Characterization of Murine Hevin (SC1), a Member of the SPARC Family of Matricellular Proteins

“…Mouse hevin (SC1) cDNA (Soderling et al 1997), minus the signal sequence, was amplified by polymerase chain reaction (PCR) using sequence-specific primers designed to generate a single product with Xba I-5 Ј and Bgl II-3 Ј sensitive ends (forward: 5 Ј -GAATTCTCTAGAGACAAGTACA-AGGTTTCTCTTTGACCAC-3 Ј ; and reverse 5 Ј -GAAT-TCAGATCTTTTTTTTTTTTTTTGGGGAGGTTTTATAG-3 Ј ). The Xba I/Bgl II-digested PCR product was subcloned into the pAcGP67A baculovirus expression vector (Pharmingen; San Diego, CA) in frame with the viral gp67 signal sequence to allow efficient protein secretion of hevin by virally-transfected Spodoptera frugiperda 9 (Sf 9) cells, which were propagated in TMN-FH medium supplemented with 10% fetal bovine serum (FBS; Pharmingen) at 27C.…”

Osteopenia and decreased bone formation in osteonectin-deficient mice

“…Northern blot analysis showed that control and osteonectin-null mice had similar transcript levels for the calcium-binding extracellular matrix proteins osteocalcin and osteopontin, suggesting that they may not be involved in compensating for the osteonectin-null mutation. Interestingly, SC1, which has 70% similarity to osteonectin, is coexpressed with osteonectin in embryonic bone, suggesting that osteonectin and SC1 may have redundant functions in skeletogenesis (50). Given the progressive decline in trabecular bone volume in adults, osteonectin may be more important in remodeling adult bone than in development and growth.…”

Secreted Protein Acidic and Rich in Cysteines-like 1 Suppresses Aggressiveness and Predicts Better Survival in Colorectal Cancers

“…SPARCL1 was first isolated from a human high endothelial venules cDNA library and is involved in many physiologic functions, such as cell adhesion (7,8), cell proliferation (7), central nervous system development (9), and B-lymphocyte maturation (10). SPARCL1 is widely expressed in normal tissues such as brain, heart, lung, muscle, colon, and kidney (5,6,(11)(12)(13). In contrast, its full-length expression was strongly downregulated in several carcinomas such as metastatic prostate adenocarcinoma and non-small cell lung cancer (5,8,(14)(15)(16).…”