SC1, A SPARC-related glycoprotein, exhibits features of an ECM component in the developing and adult brain

Mendis, Duane B.; Shahin, Susan; Gurd, James W.; Brown, Ian R.

doi:10.1016/0006-8993(95)01472-1

Cited by 39 publications

(36 citation statements)

References 42 publications

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“…Our identification of SPARC in the adult and newborn bovine retina, together with the demonstration of SPARC family proteins SC1 and QR1 in the central nervous system (Casado et al 1996;Mendis et al 1996b), suggests that SPARC and SPARC-like proteins are important not only in development of the retina but also in maintenance of its normal functions in the mature retina. More detailed study will be required to elucidate the precise functions of these proteins in both the developing and the mature retina.…”

Section: Discussionmentioning

confidence: 76%

SPARC Is Expressed by Ganglion Cells and Astrocytes in Bovine Retina

Yan

Sage

Hendrickson

1998

J Histochem Cytochem.

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SUMMARY SPARC (secreted protein, acidic and rich in cysteine) ր osteonectin is a matricellular, counteradhesive glycoprotein that disrupts cell-matrix interactions, interacts with growth factors and components of extracellular matrix, and modulates the cell cycle, but appears to subserve only minor structural roles. SPARC is expressed in a variety of tissues during embryogenesis and remodeling and is believed to regulate vascular morphogenesis and cellular differentiation. Although usually limited in normal adult tissues, SPARC is expressed at significant levels in the adult central nervous system. Using a monoclonal antibody against bovine bone osteonectin, we have determined the localization of SPARC in newborn (3-day-old) and adult (4-8-year-old) normal bovine retinas. SPARC was present in the soma of ganglion cells and strong reactivity was found in ganglion cell axons. Muller cells displayed no immunoreactivity, but SPARC was present in retinal astrocytes that were identified by the astrocyte marker glial fibrillary acidic protein (GFAP). Newborn calf retina showed a staining pattern similar to that of adult retina but exhibited significantly reduced levels of SPARC. Minimal levels of SPARC protein were also detected in some capillaries of the inner retina of both newborn and adult animals, whereas large vessels were negative. The presence of SPARC in the retina was confirmed by Western blotting of retinal extracts. These data indicate that SPARC originating from both neurons and glia of the inner retina may be an important modulator of retinal angiogenesis. The increased expression of SPARC in adult relative to newborn retinal tissue also indicates that SPARC has an ongoing role in the maintainance of retinal functions. (J Histochem Cytochem 46:3-10, 1998)

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Section: Discussionmentioning

confidence: 76%

SPARC Is Expressed by Ganglion Cells and Astrocytes in Bovine Retina

Yan

Sage

Hendrickson

1998

J Histochem Cytochem.

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“…These authors also found that SPARC was expressed in the adult brain by astrocytes in synapse-enriched regions and suggested a role for SPARC in neural plasticity (Mendis et al 1995). Moreover, the cytokine-binding follistatin region in both of these proteins has been suggested to function in neural differentiation through the accumulation, protection, and regulation of the activity of growth factors (Mendis et al 1996).…”

Section: Discussionmentioning

confidence: 94%

“…Mendis et al (1996) have shown an increase in SC1 during development of the brain, with the highest levels in the adult associated with neurons and synaptosomes. These authors also found that SPARC was expressed in the adult brain by astrocytes in synapse-enriched regions and suggested a role for SPARC in neural plasticity (Mendis et al 1995).…”

Section: Discussionmentioning

confidence: 99%

“…The SC1 expressed by Bergmann glial cells is deposited along the length of their radial fibers during the process of granule cell migration in the developing cerebellum . Subcellular fractionation demonstrated that the SC1 116/120-kD doublet is associated with synaptosomes (Mendis et al 1996). Hevin, the human homologue of SC1 which has been isolated from high endothelial venules found in tonsils (Girard and Springer 1995), inhibits attachment and spreading of endothelial cells on fibronectin substrates (Girard and Springer 1996).…”

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confidence: 99%

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

Soderling

Reed

Corsa

et al. 1997

J Histochem Cytochem.

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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)

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“…While the ECM is a critical modulator of spatial and temporal information during development, there are many matrix components whose function are unknown. One such protein is Sc1.Sc1 is abundantly expressed in the adult nervous system and heart (11,17,21). Sc1 is also found in the high endothelial venules of the immune system, where it has been suggested to function in lymphocyte extravasation (6).…”

mentioning

confidence: 99%

Extracellular Matrix-Associated Protein Sc1 Is Not Essential for Mouse Development

McKinnon

McLaughlin

Kapsetaki

et al. 2000

Molecular and Cellular Biology

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Sc1 is an extracellular matrix-associated protein whose function is unknown. During early embryonic development, Sc1 is widely expressed, and from embryonic day 12 (E12), Sc1 is expressed primarily in the developing nervous system. This switch in Sc1 expression at E12 suggests an importance for nervous-system development. To gain insight into Sc1 function, we used gene targeting to inactivate mouse Sc1. The Sc1-null mice showed no obvious deficits in any organs. These mice were born at the expected ratios, were fertile, and had no obvious histological abnormalities, and their long-term survival did not differ from littermate controls. Therefore, the function of Sc1 during development is not critical or, in its absence, is subserved by another protein.Molecules of the extracellular matrix (ECM) show definite patterns of spatial and temporal regulation and are critical for a wide range of events during development. For example, development of the nervous system requires ECM components for axonal target finding, neural crest guidance, and normal tissue morphogenesis (33,36,37). While the ECM is a critical modulator of spatial and temporal information during development, there are many matrix components whose function are unknown. One such protein is Sc1.Sc1 is abundantly expressed in the adult nervous system and heart (11,17,21). Sc1 is also found in the high endothelial venules of the immune system, where it has been suggested to function in lymphocyte extravasation (6). Sc1 is a member of a gene family that includes Sparc, testican, Qr1, agrin, and follistatin (1,8,25,35). The similarity of Sc1 to members of this family, which varies from 30 to 65% amino acid identity, is by virtue of a 230-amino-acid stretch at the carboxyl terminus of the molecule, suggesting functional conservation of this region. However, Sc1 also contains a unique amino terminus (ϳ400 amino acids), which shows no similarity to any protein sequence in the current gene databases. The region of Sc1 encoding the carboxy terminus contains a similar exon structure to that of Sparc, suggesting that these two genes evolved from a common ancestral gene and may have related functions (16).Sparc is highly expressed in bone (hence its alternative name, osteonectin), as well as a number of other tissues (12,20,23,32). Sparc has been implicated in angiogenesis (27, 30), and both Sc1 and Sparc are associated with astrocytes in the adult rodent brain (17,19). Because astrocytes are required for maintenance of the blood-brain barrier and a nutrient supply interface between capillary blood supply and neurons (34), the presence of Sc1 and Sparc in astrocytes supports a role in angiogenesis. The upregulation of Sc1 and Sparc after neural injury (4, 17) may also suggest a role in tissue remodeling or repair.Sparc is able to modulate platelet-derived growth factor binding to its receptor, and this affects cell cycle progression in certain endothelial cell lines (2, 3); the follistatin-like module present in Sparc (and Sc1) may be responsible for this cytokine reg...

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SC1, A SPARC-related glycoprotein, exhibits features of an ECM component in the developing and adult brain

Cited by 39 publications

References 42 publications

SPARC Is Expressed by Ganglion Cells and Astrocytes in Bovine Retina

SPARC Is Expressed by Ganglion Cells and Astrocytes in Bovine Retina

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

Extracellular Matrix-Associated Protein Sc1 Is Not Essential for Mouse Development

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